From ef5111810845344f23c8a68db1d41d089d0618a5 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 10:11:52 -0700
Subject: [PATCH 01/28] fix

---
 src/passes/CMakeLists.txt    |   1 +
 src/passes/PrintBoundary.cpp | 138 +++++++++++++++++++++++++++++++++++
 src/passes/pass.cpp          |   2 +
 src/passes/passes.h          |   1 +
 4 files changed, 142 insertions(+)
 create mode 100644 src/passes/PrintBoundary.cpp

diff --git a/src/passes/CMakeLists.txt b/src/passes/CMakeLists.txt
index a61bfb6195c..d6f9100aad0 100644
--- a/src/passes/CMakeLists.txt
+++ b/src/passes/CMakeLists.txt
@@ -89,6 +89,7 @@ set(passes_SOURCES
   PostEmscripten.cpp
   Precompute.cpp
   Print.cpp
+  PrintBoundary.cpp
   PrintCallGraph.cpp
   PrintFeatures.cpp
   PrintFunctionMap.cpp
diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
new file mode 100644
index 00000000000..7cf772f9e43
--- /dev/null
+++ b/src/passes/PrintBoundary.cpp
@@ -0,0 +1,138 @@
+/*
+ * Copyright 2026 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//
+// Prints the boundary - the imports and exports - in a convenient JSON format.
+// Only enough information for JavaScript is provided (for the full info, parse
+// the wat or wasm).
+//
+// Usage:
+//
+//    wasm-opt --print-boundary=OUTFILE
+//
+// If OUTFILE is not provided, prints to stdout.
+//
+// Example:
+//
+//  {
+//    'imports': [
+//      {
+//        'name': 'foo',
+//        'kind': 'func',
+//        'params': ['i32', '(ref func)'],
+//        'results': ['f64']
+//      },
+//      [..]
+//    ],
+//    'exports': [
+//      {
+//        'name': 'foo',
+//        'kind': 'global',
+//        'type': 'i32',
+//      },
+//      [..]
+//    ]
+//  }
+//
+
+#include "pass.h"
+#include "support/file.h"
+#include "wasm.h"
+
+namespace wasm {
+
+struct PrintCallGraph : public Pass {
+  bool modifiesBinaryenIR() override { return false; }
+
+  void run(Module* module) override {
+    std::string target = getArgumentOrDefault("print-boundary", "");
+
+    Output out(target, Flags::BinaryOption::Text);
+
+    std::ostream& o = std::cout;
+    o << "digraph call {\n"
+         "  rankdir = LR;\n"
+         "  subgraph cluster_key {\n"
+         "    node [shape=box, fontname=courier, fontsize=10];\n"
+         "    edge [fontname=courier, fontsize=10];\n"
+         "    label = \"Key\";\n"
+         "    \"Import\" [style=\"filled\", fillcolor=\"turquoise\"];\n"
+         "    \"Export\" [style=\"filled\", fillcolor=\"gray\"];\n"
+         "    \"Indirect Target\" [style=\"filled, rounded\", "
+         "fillcolor=\"white\"];\n"
+         "    \"A\" -> \"B\" [style=\"filled, rounded\", label = \"Direct "
+         "Call\"];\n"
+         "  }\n\n"
+         "  node [shape=box, fontname=courier, fontsize=10];\n";
+
+    // Defined functions
+    ModuleUtils::iterDefinedFunctions(*module, [&](Function* curr) {
+      std::cout << "  \"" << curr->name
+                << "\" [style=\"filled\", fillcolor=\"white\"];\n";
+    });
+
+    // Imported functions
+    ModuleUtils::iterImportedFunctions(*module, [&](Function* curr) {
+      o << "  \"" << curr->name
+        << "\" [style=\"filled\", fillcolor=\"turquoise\"];\n";
+    });
+
+    // Exports
+    for (auto& curr : module->exports) {
+      if (curr->kind == ExternalKind::Function) {
+        Function* func = module->getFunction(*curr->getInternalName());
+        o << "  \"" << func->name
+          << "\" [style=\"filled\", fillcolor=\"gray\"];\n";
+      }
+    }
+
+    struct CallPrinter : public PostWalker<CallPrinter> {
+      Module* module;
+      Function* currFunction;
+      std::set<Name> visitedTargets; // Used to avoid printing duplicate edges.
+      std::vector<Function*> allIndirectTargets;
+      CallPrinter(Module* module) : module(module) {
+        // Walk function bodies.
+        ModuleUtils::iterDefinedFunctions(*module, [&](Function* curr) {
+          currFunction = curr;
+          visitedTargets.clear();
+          walk(curr->body);
+        });
+      }
+      void visitCall(Call* curr) {
+        auto* target = module->getFunction(curr->target);
+        if (!visitedTargets.emplace(target->name).second) {
+          return;
+        }
+        std::cout << "  \"" << currFunction->name << "\" -> \"" << target->name
+                  << "\"; // call\n";
+      }
+    };
+    CallPrinter printer(module);
+
+    // Indirect Targets
+    ElementUtils::iterAllElementFunctionNames(module, [&](Name name) {
+      auto* func = module->getFunction(name);
+      o << "  \"" << func->name << "\" [style=\"filled, rounded\"];\n";
+    });
+
+    o << "}\n";
+  }
+};
+
+Pass* createPrintCallGraphPass() { return new PrintCallGraph(); }
+
+} // namespace wasm
diff --git a/src/passes/pass.cpp b/src/passes/pass.cpp
index dc6d91feb4e..d29a6fcebf5 100644
--- a/src/passes/pass.cpp
+++ b/src/passes/pass.cpp
@@ -390,6 +390,8 @@ void PassRegistry::registerPasses() {
                createPrintFeaturesPass);
   registerPass(
     "print-full", "print in full s-expression format", createFullPrinterPass);
+  registerPass(
+    "print-boundary", "print boundary in JSON format", createPrintBoundaryPass);
   registerPass(
     "print-call-graph", "print call graph", createPrintCallGraphPass);
 
diff --git a/src/passes/passes.h b/src/passes/passes.h
index 2fdacd84ab0..d7f272bbbb6 100644
--- a/src/passes/passes.h
+++ b/src/passes/passes.h
@@ -128,6 +128,7 @@ Pass* createPostEmscriptenPass();
 Pass* createPrecomputePass();
 Pass* createPrecomputePropagatePass();
 Pass* createPrinterPass();
+Pass* createprintBoundaryPass();
 Pass* createPrintCallGraphPass();
 Pass* createPrintFeaturesPass();
 Pass* createPrintFunctionMapPass();

From 8cf542b28224f6ea753ffaa6bb4e5183cf964d23 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 11:15:10 -0700
Subject: [PATCH 02/28] go

---
 src/passes/PrintBoundary.cpp | 102 +++++++++++++----------------------
 src/passes/passes.h          |   2 +-
 src/support/json.h           |   2 +
 3 files changed, 39 insertions(+), 67 deletions(-)

diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
index 7cf772f9e43..2a9e54351cf 100644
--- a/src/passes/PrintBoundary.cpp
+++ b/src/passes/PrintBoundary.cpp
@@ -30,7 +30,8 @@
 //  {
 //    'imports': [
 //      {
-//        'name': 'foo',
+//        'module': 'foo', // foo.bar
+//        'base': 'bar',
 //        'kind': 'func',
 //        'params': ['i32', '(ref func)'],
 //        'results': ['f64']
@@ -50,89 +51,58 @@
 
 #include "pass.h"
 #include "support/file.h"
+#include "support/json.h"
 #include "wasm.h"
 
 namespace wasm {
 
-struct PrintCallGraph : public Pass {
+struct PrintBoundary : public Pass {
   bool modifiesBinaryenIR() override { return false; }
 
   void run(Module* module) override {
     std::string target = getArgumentOrDefault("print-boundary", "");
 
-    Output out(target, Flags::BinaryOption::Text);
-
-    std::ostream& o = std::cout;
-    o << "digraph call {\n"
-         "  rankdir = LR;\n"
-         "  subgraph cluster_key {\n"
-         "    node [shape=box, fontname=courier, fontsize=10];\n"
-         "    edge [fontname=courier, fontsize=10];\n"
-         "    label = \"Key\";\n"
-         "    \"Import\" [style=\"filled\", fillcolor=\"turquoise\"];\n"
-         "    \"Export\" [style=\"filled\", fillcolor=\"gray\"];\n"
-         "    \"Indirect Target\" [style=\"filled, rounded\", "
-         "fillcolor=\"white\"];\n"
-         "    \"A\" -> \"B\" [style=\"filled, rounded\", label = \"Direct "
-         "Call\"];\n"
-         "  }\n\n"
-         "  node [shape=box, fontname=courier, fontsize=10];\n";
+    // Imports.
+    auto imports = json::Value::make();
+    imports->setArray();
 
-    // Defined functions
-    ModuleUtils::iterDefinedFunctions(*module, [&](Function* curr) {
-      std::cout << "  \"" << curr->name
-                << "\" [style=\"filled\", fillcolor=\"white\"];\n";
-    });
+    for (auto& func : module->functions) {
+      if (!func->imported()) {
+        continue;
+      }
 
-    // Imported functions
-    ModuleUtils::iterImportedFunctions(*module, [&](Function* curr) {
-      o << "  \"" << curr->name
-        << "\" [style=\"filled\", fillcolor=\"turquoise\"];\n";
-    });
+      auto import = json::Value::make();
+      import["module"] = json::Value::make(func->module.toString());
+      import["base"] = json::Value::make(func->base.toString());
+      import["kind"] = json::Value::make("func");
+      import["params"] = getTypes(func->getParams());
+      import["results"] = getTypes(func->getResults());
 
-    // Exports
-    for (auto& curr : module->exports) {
-      if (curr->kind == ExternalKind::Function) {
-        Function* func = module->getFunction(*curr->getInternalName());
-        o << "  \"" << func->name
-          << "\" [style=\"filled\", fillcolor=\"gray\"];\n";
-      }
+      imports->push_back(import);
     }
 
-    struct CallPrinter : public PostWalker<CallPrinter> {
-      Module* module;
-      Function* currFunction;
-      std::set<Name> visitedTargets; // Used to avoid printing duplicate edges.
-      std::vector<Function*> allIndirectTargets;
-      CallPrinter(Module* module) : module(module) {
-        // Walk function bodies.
-        ModuleUtils::iterDefinedFunctions(*module, [&](Function* curr) {
-          currFunction = curr;
-          visitedTargets.clear();
-          walk(curr->body);
-        });
-      }
-      void visitCall(Call* curr) {
-        auto* target = module->getFunction(curr->target);
-        if (!visitedTargets.emplace(target->name).second) {
-          return;
-        }
-        std::cout << "  \"" << currFunction->name << "\" -> \"" << target->name
-                  << "\"; // call\n";
-      }
-    };
-    CallPrinter printer(module);
+    // Exports.
+
+    // Emit the final structure
+    json::Value root;
+    root.setArray(2);
+    root[0] = imports;
+    //root[1] = exports;
 
-    // Indirect Targets
-    ElementUtils::iterAllElementFunctionNames(module, [&](Name name) {
-      auto* func = module->getFunction(name);
-      o << "  \"" << func->name << "\" [style=\"filled, rounded\"];\n";
-    });
+    Output output(target, Flags::BinaryOption::Text);
+    root.stringify(output.getStream(), true /* pretty */);
+  }
 
-    o << "}\n";
+  json::Value::Ref getTypes(Type type) {
+    auto ret = json::Value::make();
+    ret->setArray();
+    for (auto t : type) {
+      ret->push_back(json::Value::make(t.toString()));
+    }
+    return ret;
   }
 };
 
-Pass* createPrintCallGraphPass() { return new PrintCallGraph(); }
+Pass* createPrintBoundaryPass() { return new PrintBoundary(); }
 
 } // namespace wasm
diff --git a/src/passes/passes.h b/src/passes/passes.h
index d7f272bbbb6..681a259a831 100644
--- a/src/passes/passes.h
+++ b/src/passes/passes.h
@@ -128,7 +128,7 @@ Pass* createPostEmscriptenPass();
 Pass* createPrecomputePass();
 Pass* createPrecomputePropagatePass();
 Pass* createPrinterPass();
-Pass* createprintBoundaryPass();
+Pass* createPrintBoundaryPass();
 Pass* createPrintCallGraphPass();
 Pass* createPrintFeaturesPass();
 Pass* createPrintFunctionMapPass();
diff --git a/src/support/json.h b/src/support/json.h
index 23d0749f045..7c4d2d9e55d 100644
--- a/src/support/json.h
+++ b/src/support/json.h
@@ -67,6 +67,7 @@ struct Value {
     Ref& operator[](IString x) { return (*this->get())[x]; }
   };
 
+  static Ref make() { return Ref(new Value); }
   template<typename T> static Ref make(T t) { return Ref(new Value(t)); }
 
   enum Type {
@@ -102,6 +103,7 @@ struct Value {
   // constructors all copy their input
   Value() {}
   explicit Value(const char* s) : type(Null) { setString(s); }
+  explicit Value(const std::string& s) : type(Null) { setString(s.c_str()); }
   explicit Value(double n) : type(Null) { setNumber(n); }
   explicit Value(ArrayStorage& a) : type(Null) {
     setArray();

From 91ae16e545d02508bdf64bfe6f6b4fffd906064f Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 11:23:03 -0700
Subject: [PATCH 03/28] go

---
 src/passes/PrintBoundary.cpp | 37 +++++++++++++++++++++++++++++++++---
 src/support/json.h           |  1 +
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
index 2a9e54351cf..01286a6c022 100644
--- a/src/passes/PrintBoundary.cpp
+++ b/src/passes/PrintBoundary.cpp
@@ -72,8 +72,8 @@ struct PrintBoundary : public Pass {
       }
 
       auto import = json::Value::make();
-      import["module"] = json::Value::make(func->module.toString());
-      import["base"] = json::Value::make(func->base.toString());
+      import["module"] = json::Value::make(func->module.view());
+      import["base"] = json::Value::make(func->base.view());
       import["kind"] = json::Value::make("func");
       import["params"] = getTypes(func->getParams());
       import["results"] = getTypes(func->getResults());
@@ -82,12 +82,43 @@ struct PrintBoundary : public Pass {
     }
 
     // Exports.
+    auto exports = json::Value::make();
+    exports->setArray();
+
+    for (auto& exp : module->exports) {
+      auto export_ = json::Value::make();
+      export_["name"] = json::Value::make(exp->name.view());
+      const char* kind;
+      switch (exp->kind) {
+        case ExternalKind::Function:
+          kind = "func";
+          break;
+        case ExternalKind::Table:
+          kind = "table";
+          break;
+        case ExternalKind::Memory:
+          kind = "memory";
+          break;
+        case ExternalKind::Global:
+          kind = "global";
+          break;
+        case ExternalKind::Tag:
+          kind = "tag";
+          break;
+        case ExternalKind::Invalid:
+          WASM_UNREACHABLE("invalid ExternalKind");
+      }
+      export_["kind"] = json::Value::make(kind);
+      export_["type"] = getTypes(exp->type);
+
+      exports->push_back(export_);
+    }
 
     // Emit the final structure
     json::Value root;
     root.setArray(2);
     root[0] = imports;
-    //root[1] = exports;
+    root[1] = exports;
 
     Output output(target, Flags::BinaryOption::Text);
     root.stringify(output.getStream(), true /* pretty */);
diff --git a/src/support/json.h b/src/support/json.h
index 7c4d2d9e55d..cc02c95a465 100644
--- a/src/support/json.h
+++ b/src/support/json.h
@@ -104,6 +104,7 @@ struct Value {
   Value() {}
   explicit Value(const char* s) : type(Null) { setString(s); }
   explicit Value(const std::string& s) : type(Null) { setString(s.c_str()); }
+  explicit Value(const std::string_view& s) : type(Null) { setString(std::string(s)); }
   explicit Value(double n) : type(Null) { setNumber(n); }
   explicit Value(ArrayStorage& a) : type(Null) {
     setArray();

From 377a466109661e49ac47088dffc01c0721d581c0 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 11:36:55 -0700
Subject: [PATCH 04/28] go

---
 src/ir/module-utils.cpp      | 17 +++++++++++++
 src/ir/module-utils.h        |  3 +++
 src/passes/PrintBoundary.cpp | 49 ++++++++++++++++++++----------------
 3 files changed, 48 insertions(+), 21 deletions(-)

diff --git a/src/ir/module-utils.cpp b/src/ir/module-utils.cpp
index 6ee94d35d65..ceeea1a4b70 100644
--- a/src/ir/module-utils.cpp
+++ b/src/ir/module-utils.cpp
@@ -293,6 +293,23 @@ void clearModule(Module& wasm) {
   new (&wasm) Module;
 }
 
+Type getType(Module& wasm, ExternalKind kind, Name name) {
+  switch (kind) {
+    case ExternalKind::Function:
+      return wasm.getFunction(name)->type;
+    case ExternalKind::Table:
+      return wasm.getTable(name)->type;
+    case ExternalKind::Memory:
+      return wasm.getMemory(name)->type;
+    case ExternalKind::Global:
+      return wasm.getGlobal(name)->type;
+    case ExternalKind::Tag:
+      return wasm.getTag(name)->type;
+    case ExternalKind::Invalid:
+      WASM_UNREACHABLE("invalid ExternalKind");
+  }
+}
+
 // Renaming
 
 // Rename functions along with all their uses.
diff --git a/src/ir/module-utils.h b/src/ir/module-utils.h
index 50b67df7cea..039c90d2639 100644
--- a/src/ir/module-utils.h
+++ b/src/ir/module-utils.h
@@ -261,6 +261,9 @@ template<typename T> inline void iterModuleItems(Module& wasm, T visitor) {
   }
 }
 
+// Generic type finding of any import/export, similar to the iteration above.
+Type getType(Module& wasm, ExternalKind kind, Name name);
+
 // Helper class for performing an operation on all the functions in the module,
 // in parallel, with an Info object for each one that can contain results of
 // some computation that the operation performs.
diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
index 01286a6c022..ed4ac5a003e 100644
--- a/src/passes/PrintBoundary.cpp
+++ b/src/passes/PrintBoundary.cpp
@@ -33,8 +33,10 @@
 //        'module': 'foo', // foo.bar
 //        'base': 'bar',
 //        'kind': 'func',
-//        'params': ['i32', '(ref func)'],
-//        'results': ['f64']
+//        'type': {
+//          'params': ['i32', '(ref func)'],
+//          'results': ['f64']
+//        },
 //      },
 //      [..]
 //    ],
@@ -49,6 +51,7 @@
 //  }
 //
 
+#include "ir/module-utils.h"
 #include "pass.h"
 #include "support/file.h"
 #include "support/json.h"
@@ -66,28 +69,22 @@ struct PrintBoundary : public Pass {
     auto imports = json::Value::make();
     imports->setArray();
 
-    for (auto& func : module->functions) {
-      if (!func->imported()) {
-        continue;
-      }
-
-      auto import = json::Value::make();
-      import["module"] = json::Value::make(func->module.view());
-      import["base"] = json::Value::make(func->base.view());
-      import["kind"] = json::Value::make("func");
-      import["params"] = getTypes(func->getParams());
-      import["results"] = getTypes(func->getResults());
-
-      imports->push_back(import);
-    }
+    ModuleUtils::iterImportable(*module, [&](ExternalKind kind, Importable* import) {
+      auto item = json::Value::make();
+      item["module"] = json::Value::make(import->module.view());
+      item["base"] = json::Value::make(import->base.view());
+      item["kind"] = json::Value::make(kind);
+      item["type"] = getTypes(ModuleUtils::getType(kind, import->name));
+      imports->push_back(item);
+    });
 
     // Exports.
     auto exports = json::Value::make();
     exports->setArray();
 
     for (auto& exp : module->exports) {
-      auto export_ = json::Value::make();
-      export_["name"] = json::Value::make(exp->name.view());
+      auto item = json::Value::make();
+      item["name"] = json::Value::make(exp->name.view());
       const char* kind;
       switch (exp->kind) {
         case ExternalKind::Function:
@@ -108,10 +105,10 @@ struct PrintBoundary : public Pass {
         case ExternalKind::Invalid:
           WASM_UNREACHABLE("invalid ExternalKind");
       }
-      export_["kind"] = json::Value::make(kind);
-      export_["type"] = getTypes(exp->type);
+      item["kind"] = json::Value::make(kind);
+      item["type"] = getTypes(ModuleUtils::getType(kind, exp->getInternalName()));
 
-      exports->push_back(export_);
+      exports->push_back(item);
     }
 
     // Emit the final structure
@@ -124,7 +121,17 @@ struct PrintBoundary : public Pass {
     root.stringify(output.getStream(), true /* pretty */);
   }
 
+  // Emits an array of multivalue types. For a signature, emits params and
+  // results.
   json::Value::Ref getTypes(Type type) {
+    if (type.isSignature()) {
+      auto sig = type.getSignature();
+      auto ret= json::Value::make();
+      import["params"] = getTypes(sig.params);
+      import["results"] = getTypes(sig.results);
+      return ret;
+    }
+
     auto ret = json::Value::make();
     ret->setArray();
     for (auto t : type) {

From 573cdf1a65a9b44241d40308081559ea364f358a Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 15:00:56 -0700
Subject: [PATCH 05/28] work

---
 src/ir/module-utils.cpp      | 17 -----------------
 src/ir/module-utils.h        |  3 ---
 src/passes/PrintBoundary.cpp | 26 +++++++++++++++++++++++---
 3 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/src/ir/module-utils.cpp b/src/ir/module-utils.cpp
index ceeea1a4b70..6ee94d35d65 100644
--- a/src/ir/module-utils.cpp
+++ b/src/ir/module-utils.cpp
@@ -293,23 +293,6 @@ void clearModule(Module& wasm) {
   new (&wasm) Module;
 }
 
-Type getType(Module& wasm, ExternalKind kind, Name name) {
-  switch (kind) {
-    case ExternalKind::Function:
-      return wasm.getFunction(name)->type;
-    case ExternalKind::Table:
-      return wasm.getTable(name)->type;
-    case ExternalKind::Memory:
-      return wasm.getMemory(name)->type;
-    case ExternalKind::Global:
-      return wasm.getGlobal(name)->type;
-    case ExternalKind::Tag:
-      return wasm.getTag(name)->type;
-    case ExternalKind::Invalid:
-      WASM_UNREACHABLE("invalid ExternalKind");
-  }
-}
-
 // Renaming
 
 // Rename functions along with all their uses.
diff --git a/src/ir/module-utils.h b/src/ir/module-utils.h
index 039c90d2639..50b67df7cea 100644
--- a/src/ir/module-utils.h
+++ b/src/ir/module-utils.h
@@ -261,9 +261,6 @@ template<typename T> inline void iterModuleItems(Module& wasm, T visitor) {
   }
 }
 
-// Generic type finding of any import/export, similar to the iteration above.
-Type getType(Module& wasm, ExternalKind kind, Name name);
-
 // Helper class for performing an operation on all the functions in the module,
 // in parallel, with an Info object for each one that can contain results of
 // some computation that the operation performs.
diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
index ed4ac5a003e..3f23e843bf1 100644
--- a/src/passes/PrintBoundary.cpp
+++ b/src/passes/PrintBoundary.cpp
@@ -74,7 +74,7 @@ struct PrintBoundary : public Pass {
       item["module"] = json::Value::make(import->module.view());
       item["base"] = json::Value::make(import->base.view());
       item["kind"] = json::Value::make(kind);
-      item["type"] = getTypes(ModuleUtils::getType(kind, import->name));
+      item["type"] = getExternalType(kind, name);
       imports->push_back(item);
     });
 
@@ -106,8 +106,7 @@ struct PrintBoundary : public Pass {
           WASM_UNREACHABLE("invalid ExternalKind");
       }
       item["kind"] = json::Value::make(kind);
-      item["type"] = getTypes(ModuleUtils::getType(kind, exp->getInternalName()));
-
+      item["type"] = getExternalType(kind, exp->getInternalName());
       exports->push_back(item);
     }
 
@@ -139,6 +138,27 @@ struct PrintBoundary : public Pass {
     }
     return ret;
   }
+
+  // For an imported or exported thing (something external), and its name,
+  // return the type info we report for it.
+  json::Value::Ref getExternalType(ExternalKind kind, Name name) {
+    switch (kind) {
+      case ExternalKind::Function:
+        return getTypes(wasm.getFunction(name)->type);
+        break;
+      case ExternalKind::Table:
+        break;
+      case ExternalKind::Memory:
+        break;
+      case ExternalKind::Global:
+        return getTypes(wasm.getGlobal(name)->type);
+      case ExternalKind::Tag:
+        break;
+      case ExternalKind::Invalid:
+        WASM_UNREACHABLE("invalid ExternalKind");
+    }
+    return {};
+  }
 };
 
 Pass* createPrintBoundaryPass() { return new PrintBoundary(); }

From 88d29d177d0b43d0f3aeb02e6da6ba571bffebd6 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 15:07:58 -0700
Subject: [PATCH 06/28] work

---
 src/passes/PrintBoundary.cpp | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
index 3f23e843bf1..4e2587a3feb 100644
--- a/src/passes/PrintBoundary.cpp
+++ b/src/passes/PrintBoundary.cpp
@@ -74,7 +74,7 @@ struct PrintBoundary : public Pass {
       item["module"] = json::Value::make(import->module.view());
       item["base"] = json::Value::make(import->base.view());
       item["kind"] = json::Value::make(kind);
-      item["type"] = getExternalType(kind, name);
+      item["type"] = getExternalType(kind, name, *module);
       imports->push_back(item);
     });
 
@@ -106,7 +106,7 @@ struct PrintBoundary : public Pass {
           WASM_UNREACHABLE("invalid ExternalKind");
       }
       item["kind"] = json::Value::make(kind);
-      item["type"] = getExternalType(kind, exp->getInternalName());
+      item["type"] = getExternalType(exp->kind, *exp->getInternalName(), *module);
       exports->push_back(item);
     }
 
@@ -123,12 +123,15 @@ struct PrintBoundary : public Pass {
   // Emits an array of multivalue types. For a signature, emits params and
   // results.
   json::Value::Ref getTypes(Type type) {
-    if (type.isSignature()) {
-      auto sig = type.getSignature();
-      auto ret= json::Value::make();
-      import["params"] = getTypes(sig.params);
-      import["results"] = getTypes(sig.results);
-      return ret;
+    if (type.isRef()) {
+      auto heapType = type.getHeapType();
+      if (heapType.isSignature()) {
+        auto sig = heapType.getSignature();
+        auto ret= json::Value::make();
+        ret["params"] = getTypes(sig.params);
+        ret["results"] = getTypes(sig.results);
+        return ret;
+      }
     }
 
     auto ret = json::Value::make();
@@ -141,7 +144,7 @@ struct PrintBoundary : public Pass {
 
   // For an imported or exported thing (something external), and its name,
   // return the type info we report for it.
-  json::Value::Ref getExternalType(ExternalKind kind, Name name) {
+  json::Value::Ref getExternalType(ExternalKind kind, Name name, Module& wasm) {
     switch (kind) {
       case ExternalKind::Function:
         return getTypes(wasm.getFunction(name)->type);

From 97843d5a7eda5dead04cec018b2f46ebc2bf4a03 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 15:08:39 -0700
Subject: [PATCH 07/28] work

---
 src/passes/PrintBoundary.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
index 4e2587a3feb..4ae148b3c24 100644
--- a/src/passes/PrintBoundary.cpp
+++ b/src/passes/PrintBoundary.cpp
@@ -85,7 +85,7 @@ struct PrintBoundary : public Pass {
     for (auto& exp : module->exports) {
       auto item = json::Value::make();
       item["name"] = json::Value::make(exp->name.view());
-      const char* kind;
+      const char* kind = nullptr;
       switch (exp->kind) {
         case ExternalKind::Function:
           kind = "func";

From 4354d3e06d40157cb63046063669979de13efe50 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 15:23:39 -0700
Subject: [PATCH 08/28] work

---
 src/passes/PrintBoundary.cpp | 12 ++++++------
 src/support/json.h           |  7 ++++++-
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
index 4ae148b3c24..9a198aa5055 100644
--- a/src/passes/PrintBoundary.cpp
+++ b/src/passes/PrintBoundary.cpp
@@ -66,11 +66,11 @@ struct PrintBoundary : public Pass {
     std::string target = getArgumentOrDefault("print-boundary", "");
 
     // Imports.
-    auto imports = json::Value::make();
+    auto imports = json::Value::makeObject();
     imports->setArray();
 
     ModuleUtils::iterImportable(*module, [&](ExternalKind kind, Importable* import) {
-      auto item = json::Value::make();
+      auto item = json::Value::makeObject();
       item["module"] = json::Value::make(import->module.view());
       item["base"] = json::Value::make(import->base.view());
       item["kind"] = json::Value::make(kind);
@@ -79,11 +79,11 @@ struct PrintBoundary : public Pass {
     });
 
     // Exports.
-    auto exports = json::Value::make();
+    auto exports = json::Value::makeObject();
     exports->setArray();
 
     for (auto& exp : module->exports) {
-      auto item = json::Value::make();
+      auto item = json::Value::makeObject();
       item["name"] = json::Value::make(exp->name.view());
       const char* kind = nullptr;
       switch (exp->kind) {
@@ -127,14 +127,14 @@ struct PrintBoundary : public Pass {
       auto heapType = type.getHeapType();
       if (heapType.isSignature()) {
         auto sig = heapType.getSignature();
-        auto ret= json::Value::make();
+        auto ret= json::Value::makeObject();
         ret["params"] = getTypes(sig.params);
         ret["results"] = getTypes(sig.results);
         return ret;
       }
     }
 
-    auto ret = json::Value::make();
+    auto ret = json::Value::makeObject();
     ret->setArray();
     for (auto t : type) {
       ret->push_back(json::Value::make(t.toString()));
diff --git a/src/support/json.h b/src/support/json.h
index cc02c95a465..40c02328275 100644
--- a/src/support/json.h
+++ b/src/support/json.h
@@ -67,9 +67,14 @@ struct Value {
     Ref& operator[](IString x) { return (*this->get())[x]; }
   };
 
-  static Ref make() { return Ref(new Value); }
   template<typename T> static Ref make(T t) { return Ref(new Value(t)); }
 
+  static Ref makeObject() {
+    Ref ret(new Value);
+    ret->setObject();
+    return ret;
+  }
+
   enum Type {
     String = 0,
     Number = 1,

From a3e30c6f8fb11cd584e427385a74ee02b5568645 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 15:41:37 -0700
Subject: [PATCH 09/28] work

---
 src/passes/PrintBoundary.cpp |  8 ++---
 src/support/json.cpp         | 70 +++++++++++++++++++++++++-----------
 src/support/json.h           |  7 +++-
 3 files changed, 59 insertions(+), 26 deletions(-)

diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
index 9a198aa5055..1816b239be7 100644
--- a/src/passes/PrintBoundary.cpp
+++ b/src/passes/PrintBoundary.cpp
@@ -74,7 +74,7 @@ struct PrintBoundary : public Pass {
       item["module"] = json::Value::make(import->module.view());
       item["base"] = json::Value::make(import->base.view());
       item["kind"] = json::Value::make(kind);
-      item["type"] = getExternalType(kind, name, *module);
+      item["type"] = getExternalType(kind, import->name, *module);
       imports->push_back(item);
     });
 
@@ -112,9 +112,9 @@ struct PrintBoundary : public Pass {
 
     // Emit the final structure
     json::Value root;
-    root.setArray(2);
-    root[0] = imports;
-    root[1] = exports;
+    root.setArray();
+    root.push_back(imports);
+    root.push_back(exports);
 
     Output output(target, Flags::BinaryOption::Text);
     root.stringify(output.getStream(), true /* pretty */);
diff --git a/src/support/json.cpp b/src/support/json.cpp
index ff393317410..7067b16e9d3 100644
--- a/src/support/json.cpp
+++ b/src/support/json.cpp
@@ -20,29 +20,57 @@
 namespace json {
 
 void Value::stringify(std::ostream& os, bool pretty) {
-  if (isString()) {
-    std::stringstream wtf16;
-    [[maybe_unused]] bool valid =
-      wasm::String::convertWTF8ToWTF16(wtf16, getIString().view());
-    assert(valid);
-    // TODO: Use wtf16.view() once we have C++20.
-    wasm::String::printEscapedJSON(os, wtf16.str());
-  } else if (isArray()) {
-    os << '[';
-    auto first = true;
-    for (auto& item : getArray()) {
-      if (first) {
-        first = false;
-      } else {
-        // TODO pretty whitespace
-        os << ',';
+  switch (type) {
+    case String: {
+      std::stringstream wtf16;
+      [[maybe_unused]] bool valid =
+        wasm::String::convertWTF8ToWTF16(wtf16, getIString().view());
+      assert(valid);
+      // TODO: Use wtf16.view() once we have C++20.
+      wasm::String::printEscapedJSON(os, wtf16.str());
+      return;
+    }
+    case Array: {
+      os << '[';
+      auto first = true;
+      for (auto& item : getArray()) {
+        if (first) {
+          first = false;
+        } else {
+          // TODO pretty whitespace
+          os << ',';
+        }
+        item->stringify(os, pretty);
+      }
+      os << ']';
+      return;
+    }
+    case Object: {
+      os << '{';
+      auto first = true;
+      for (auto& [key, value] : getObject()) {
+        if (first) {
+          first = false;
+        } else {
+          // TODO pretty whitespace
+          os << ',';
+        }
+        os << "\"" << key << "\": ";
+        value->stringify(os, pretty);
       }
-      item->stringify(os, pretty);
+      os << ']';
+      return;
     }
-    os << ']';
-  } else {
-    WASM_UNREACHABLE("TODO: stringify all of JSON");
-  }
+    case Number:
+      os << getNumber();
+      return;
+    case Null:
+      os << "null";
+      return;
+    case Bool:
+      os << (getBool() ? "true" : "false");
+      return;
+  };
 }
 
 } // namespace json
diff --git a/src/support/json.h b/src/support/json.h
index 40c02328275..70bdc6a2792 100644
--- a/src/support/json.h
+++ b/src/support/json.h
@@ -37,6 +37,7 @@
 #include <unordered_set>
 #include <vector>
 
+#include "support/insert_ordered.h"
 #include "support/istring.h"
 #include "support/safe_integer.h"
 #include "support/string.h"
@@ -87,7 +88,7 @@ struct Value {
   Type type = Null;
 
   using ArrayStorage = std::vector<Ref>;
-  using ObjectStorage = std::unordered_map<IString, Ref>;
+  using ObjectStorage = wasm::InsertOrderedMap<IString, Ref>;
 
   // MSVC does not allow unrestricted unions:
   // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2544.pdf
@@ -210,6 +211,10 @@ struct Value {
     assert(isArray());
     return *arr;
   }
+  ObjectStorage& getObject() {
+    assert(isObject());
+    return *obj;
+  }
   bool& getBool() {
     assert(isBool());
     return boo;

From 56ea60e9815aad9ef739b18c45eb60d310a0a1b4 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 15:52:46 -0700
Subject: [PATCH 10/28] work

---
 src/passes/PrintBoundary.cpp |  9 +++-----
 src/support/json.cpp         | 40 +++++++++++++++++++++++++++++++-----
 src/support/json.h           |  9 ++++++--
 test/gtest/json.cpp          | 14 ++++++++++++-
 4 files changed, 58 insertions(+), 14 deletions(-)

diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
index 1816b239be7..ad4c1157042 100644
--- a/src/passes/PrintBoundary.cpp
+++ b/src/passes/PrintBoundary.cpp
@@ -66,8 +66,7 @@ struct PrintBoundary : public Pass {
     std::string target = getArgumentOrDefault("print-boundary", "");
 
     // Imports.
-    auto imports = json::Value::makeObject();
-    imports->setArray();
+    auto imports = json::Value::makeArray();
 
     ModuleUtils::iterImportable(*module, [&](ExternalKind kind, Importable* import) {
       auto item = json::Value::makeObject();
@@ -79,8 +78,7 @@ struct PrintBoundary : public Pass {
     });
 
     // Exports.
-    auto exports = json::Value::makeObject();
-    exports->setArray();
+    auto exports = json::Value::makeArray();
 
     for (auto& exp : module->exports) {
       auto item = json::Value::makeObject();
@@ -134,8 +132,7 @@ struct PrintBoundary : public Pass {
       }
     }
 
-    auto ret = json::Value::makeObject();
-    ret->setArray();
+    auto ret = json::Value::makeArray();
     for (auto t : type) {
       ret->push_back(json::Value::make(t.toString()));
     }
diff --git a/src/support/json.cpp b/src/support/json.cpp
index 7067b16e9d3..03757adf8ab 100644
--- a/src/support/json.cpp
+++ b/src/support/json.cpp
@@ -19,7 +19,13 @@
 
 namespace json {
 
-void Value::stringify(std::ostream& os, bool pretty) {
+void Value::stringify(std::ostream& os, bool pretty, int indent) {
+  auto doIndent = [&]() {
+    for (int i = 0; i < indent; i++) {
+      os << ' ';
+    }
+  };
+
   switch (type) {
     case String: {
       std::stringstream wtf16;
@@ -32,31 +38,55 @@ void Value::stringify(std::ostream& os, bool pretty) {
     }
     case Array: {
       os << '[';
+      indent++;
       auto first = true;
       for (auto& item : getArray()) {
         if (first) {
           first = false;
         } else {
-          // TODO pretty whitespace
           os << ',';
+          if (pretty) {
+            os << ' ';
+          }
+        }
+        if (pretty) {
+          os << '\n';
+          doIndent();
         }
-        item->stringify(os, pretty);
+        item->stringify(os, pretty, indent + 1);
+      }
+      indent--;
+      if (pretty) {
+        os << '\n';
+        doIndent();
       }
       os << ']';
       return;
     }
     case Object: {
       os << '{';
+      indent++;
       auto first = true;
       for (auto& [key, value] : getObject()) {
         if (first) {
           first = false;
         } else {
-          // TODO pretty whitespace
           os << ',';
+          if (pretty) {
+            os << ' ';
+          }
+        }
+        if (pretty) {
+          os << '\n';
+          doIndent();
         }
         os << "\"" << key << "\": ";
-        value->stringify(os, pretty);
+        value->stringify(os, pretty, indent + 1);
+      }
+      indent--;
+      if (pretty) {
+        os << '\n';
+        doIndent();
       }
       os << ']';
       return;
diff --git a/src/support/json.h b/src/support/json.h
index 70bdc6a2792..3a5842fe8a0 100644
--- a/src/support/json.h
+++ b/src/support/json.h
@@ -68,8 +68,13 @@ struct Value {
     Ref& operator[](IString x) { return (*this->get())[x]; }
   };
 
+  static Ref make() { return Ref(new Value); }
   template<typename T> static Ref make(T t) { return Ref(new Value(t)); }
-
+  static Ref makeArray() {
+    Ref ret(new Value);
+    ret->setArray();
+    return ret;
+  }
   static Ref makeObject() {
     Ref ret(new Value);
     ret->setObject();
@@ -391,7 +396,7 @@ struct Value {
     return curr;
   }
 
-  void stringify(std::ostream& os, bool pretty = false);
+  void stringify(std::ostream& os, bool pretty = false, int indent = 0);
 
   // String operations
 
diff --git a/test/gtest/json.cpp b/test/gtest/json.cpp
index 626861a626a..0fa2e76d9ca 100644
--- a/test/gtest/json.cpp
+++ b/test/gtest/json.cpp
@@ -3,7 +3,19 @@
 
 using JSONTest = ::testing::Test;
 
-TEST_F(JSONTest, Stringify) {
+TEST_F(JSONTest, RoundtripString) {
+  // TODO: change the API to not require a copy
+  auto input = "[\"hello\",\"world\"]";
+  auto* copy = strdup(input);
+  json::Value value;
+  value.parse(copy, json::Value::ASCII);
+  std::stringstream ss;
+  value.stringify(ss);
+  EXPECT_EQ(ss.str(), input);
+  free(copy);
+}
+
+TEST_F(JSONTest, StringifyArray) {
   // TODO: change the API to not require a copy
   auto input = "[\"hello\",\"world\"]";
   auto* copy = strdup(input);

From fb5ff358515891782cc8672428003ee0bf490a4f Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 16:00:54 -0700
Subject: [PATCH 11/28] work

---
 src/support/json.cpp |  6 ------
 test/gtest/json.cpp  | 27 ++++++++++++++++++---------
 2 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/src/support/json.cpp b/src/support/json.cpp
index 03757adf8ab..2638ca2bfee 100644
--- a/src/support/json.cpp
+++ b/src/support/json.cpp
@@ -45,9 +45,6 @@ void Value::stringify(std::ostream& os, bool pretty, int indent) {
           first = false;
         } else {
           os << ',';
-          if (pretty) {
-            os << ' ';
-          }
         }
         if (pretty) {
           os << '\n';
@@ -72,9 +69,6 @@ void Value::stringify(std::ostream& os, bool pretty, int indent) {
           first = false;
         } else {
           os << ',';
-          if (pretty) {
-            os << ' ';
-          }
         }
         if (pretty) {
           os << '\n';
diff --git a/test/gtest/json.cpp b/test/gtest/json.cpp
index 0fa2e76d9ca..d0ce24c5305 100644
--- a/test/gtest/json.cpp
+++ b/test/gtest/json.cpp
@@ -15,14 +15,23 @@ TEST_F(JSONTest, RoundtripString) {
   free(copy);
 }
 
-TEST_F(JSONTest, StringifyArray) {
-  // TODO: change the API to not require a copy
-  auto input = "[\"hello\",\"world\"]";
-  auto* copy = strdup(input);
-  json::Value value;
-  value.parse(copy, json::Value::ASCII);
+static void checkOutput(json::Value::Ref ref, std::string expected, bool pretty=false) {
   std::stringstream ss;
-  value.stringify(ss);
-  EXPECT_EQ(ss.str(), input);
-  free(copy);
+  ref->stringify(ss, pretty);
+  EXPECT_EQ(ss.str(), expected);
+}
+
+static void checkPrettyOutput(json::Value::Ref ref, std::string expected) {
+  checkOutput(ref, expected, true);
+}
+
+TEST_F(JSONTest, StringifyArray) {
+  auto array = json::Value::makeArray();
+  array->push_back(json::Value::make(42));
+  array->push_back(json::Value::make("1337"));
+  checkOutput(array, "[42,\"1337\"]");
+  checkPrettyOutput(array, R"([
+ 42,
+ "1337"
+])");
 }

From b8492ff1a05b2e377ae0c7f86e3ed445b37f9ca2 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 16:11:08 -0700
Subject: [PATCH 12/28] work

---
 test/gtest/json.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/test/gtest/json.cpp b/test/gtest/json.cpp
index d0ce24c5305..2fe3981e62b 100644
--- a/test/gtest/json.cpp
+++ b/test/gtest/json.cpp
@@ -29,9 +29,11 @@ TEST_F(JSONTest, StringifyArray) {
   auto array = json::Value::makeArray();
   array->push_back(json::Value::make(42));
   array->push_back(json::Value::make("1337"));
-  checkOutput(array, "[42,\"1337\"]");
+  array->push_back(json::Value::make()); // null
+  checkOutput(array, "[42,\"1337\",null]");
   checkPrettyOutput(array, R"([
  42,
- "1337"
+ "1337",
+ null
 ])");
 }

From e5ca754122be2a15e97c335d508d4e4d63107cc7 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 16:13:53 -0700
Subject: [PATCH 13/28] work

---
 src/support/json.cpp |  7 +++++--
 test/gtest/json.cpp  | 11 +++++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/support/json.cpp b/src/support/json.cpp
index 2638ca2bfee..3d9a2f3629c 100644
--- a/src/support/json.cpp
+++ b/src/support/json.cpp
@@ -74,7 +74,10 @@ void Value::stringify(std::ostream& os, bool pretty, int indent) {
           os << '\n';
           doIndent();
         }
-        os << "\"" << key << "\": ";
+        os << "\"" << key << "\":";
+        if (pretty) {
+          os << ' ';
+        }
         value->stringify(os, pretty, indent + 1);
       }
       indent--;
@@ -82,7 +85,7 @@ void Value::stringify(std::ostream& os, bool pretty, int indent) {
         os << '\n';
         doIndent();
       }
-      os << ']';
+      os << '}';
       return;
     }
     case Number:
diff --git a/test/gtest/json.cpp b/test/gtest/json.cpp
index 2fe3981e62b..92d32e761b6 100644
--- a/test/gtest/json.cpp
+++ b/test/gtest/json.cpp
@@ -37,3 +37,14 @@ TEST_F(JSONTest, StringifyArray) {
  null
 ])");
 }
+
+TEST_F(JSONTest, StringifyObject) {
+  auto object = json::Value::makeObject();
+  object["foo"] = json::Value::make(42);
+  object["bar"] = json::Value::make("1337");
+  checkOutput(object, "{\"foo\":42,\"bar\":\"1337\"}");
+  checkPrettyOutput(object, R"({
+ "foo": 42,
+ "bar": "1337"
+})");
+}

From 5b67220f5bbe9664002cf7bb4d57270fee99c0ae Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 16:15:50 -0700
Subject: [PATCH 14/28] work

---
 test/gtest/json.cpp | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/test/gtest/json.cpp b/test/gtest/json.cpp
index 92d32e761b6..52d997dbd28 100644
--- a/test/gtest/json.cpp
+++ b/test/gtest/json.cpp
@@ -48,3 +48,24 @@ TEST_F(JSONTest, StringifyObject) {
  "bar": "1337"
 })");
 }
+
+TEST_F(JSONTest, StringifyNesting) {
+  auto array = json::Value::makeArray();
+  auto object = json::Value::makeObject();
+  auto array1 = json::Value::makeArray();
+  auto object1 = json::Value::makeObject();
+  array->push_back(object);
+  object["body"] = array1;
+  array1->push_back(object1);
+  object1["value"] = json::Value::make(42);
+  checkPrettyOutput(array, R"([
+ {
+  "body": [
+   {
+    "
+ 42,
+ "1337",
+ null
+])");
+}
+

From c23c910a358658c2f1097493aa47df192684a9b9 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 16:20:21 -0700
Subject: [PATCH 15/28] work

---
 src/support/json.cpp | 4 ++--
 test/gtest/json.cpp  | 8 ++++----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/support/json.cpp b/src/support/json.cpp
index 3d9a2f3629c..506f9cc475f 100644
--- a/src/support/json.cpp
+++ b/src/support/json.cpp
@@ -50,7 +50,7 @@ void Value::stringify(std::ostream& os, bool pretty, int indent) {
           os << '\n';
           doIndent();
         }
-        item->stringify(os, pretty, indent + 1);
+        item->stringify(os, pretty, indent);
       }
       indent--;
       if (pretty) {
@@ -78,7 +78,7 @@ void Value::stringify(std::ostream& os, bool pretty, int indent) {
         if (pretty) {
           os << ' ';
         }
-        value->stringify(os, pretty, indent + 1);
+        value->stringify(os, pretty, indent);
       }
       indent--;
       if (pretty) {
diff --git a/test/gtest/json.cpp b/test/gtest/json.cpp
index 52d997dbd28..bcb12470c5c 100644
--- a/test/gtest/json.cpp
+++ b/test/gtest/json.cpp
@@ -62,10 +62,10 @@ TEST_F(JSONTest, StringifyNesting) {
  {
   "body": [
    {
-    "
- 42,
- "1337",
- null
+    "value": 42
+   }
+  ]
+ }
 ])");
 }
 

From a2812a0caf47cecc87c18e04e432beedc20fce4f Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 16:20:38 -0700
Subject: [PATCH 16/28] format

---
 src/passes/PrintBoundary.cpp | 22 ++++++++++++----------
 src/support/json.h           |  4 +++-
 test/gtest/json.cpp          |  4 ++--
 3 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
index ad4c1157042..0c237736763 100644
--- a/src/passes/PrintBoundary.cpp
+++ b/src/passes/PrintBoundary.cpp
@@ -68,14 +68,15 @@ struct PrintBoundary : public Pass {
     // Imports.
     auto imports = json::Value::makeArray();
 
-    ModuleUtils::iterImportable(*module, [&](ExternalKind kind, Importable* import) {
-      auto item = json::Value::makeObject();
-      item["module"] = json::Value::make(import->module.view());
-      item["base"] = json::Value::make(import->base.view());
-      item["kind"] = json::Value::make(kind);
-      item["type"] = getExternalType(kind, import->name, *module);
-      imports->push_back(item);
-    });
+    ModuleUtils::iterImportable(
+      *module, [&](ExternalKind kind, Importable* import) {
+        auto item = json::Value::makeObject();
+        item["module"] = json::Value::make(import->module.view());
+        item["base"] = json::Value::make(import->base.view());
+        item["kind"] = json::Value::make(kind);
+        item["type"] = getExternalType(kind, import->name, *module);
+        imports->push_back(item);
+      });
 
     // Exports.
     auto exports = json::Value::makeArray();
@@ -104,7 +105,8 @@ struct PrintBoundary : public Pass {
           WASM_UNREACHABLE("invalid ExternalKind");
       }
       item["kind"] = json::Value::make(kind);
-      item["type"] = getExternalType(exp->kind, *exp->getInternalName(), *module);
+      item["type"] =
+        getExternalType(exp->kind, *exp->getInternalName(), *module);
       exports->push_back(item);
     }
 
@@ -125,7 +127,7 @@ struct PrintBoundary : public Pass {
       auto heapType = type.getHeapType();
       if (heapType.isSignature()) {
         auto sig = heapType.getSignature();
-        auto ret= json::Value::makeObject();
+        auto ret = json::Value::makeObject();
         ret["params"] = getTypes(sig.params);
         ret["results"] = getTypes(sig.results);
         return ret;
diff --git a/src/support/json.h b/src/support/json.h
index 3a5842fe8a0..98e46b063fd 100644
--- a/src/support/json.h
+++ b/src/support/json.h
@@ -115,7 +115,9 @@ struct Value {
   Value() {}
   explicit Value(const char* s) : type(Null) { setString(s); }
   explicit Value(const std::string& s) : type(Null) { setString(s.c_str()); }
-  explicit Value(const std::string_view& s) : type(Null) { setString(std::string(s)); }
+  explicit Value(const std::string_view& s) : type(Null) {
+    setString(std::string(s));
+  }
   explicit Value(double n) : type(Null) { setNumber(n); }
   explicit Value(ArrayStorage& a) : type(Null) {
     setArray();
diff --git a/test/gtest/json.cpp b/test/gtest/json.cpp
index bcb12470c5c..5cd737ac6df 100644
--- a/test/gtest/json.cpp
+++ b/test/gtest/json.cpp
@@ -15,7 +15,8 @@ TEST_F(JSONTest, RoundtripString) {
   free(copy);
 }
 
-static void checkOutput(json::Value::Ref ref, std::string expected, bool pretty=false) {
+static void
+checkOutput(json::Value::Ref ref, std::string expected, bool pretty = false) {
   std::stringstream ss;
   ref->stringify(ss, pretty);
   EXPECT_EQ(ss.str(), expected);
@@ -68,4 +69,3 @@ TEST_F(JSONTest, StringifyNesting) {
  }
 ])");
 }
-

From 6b1ea4a352922b0183d011310b344cb04e805446 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 16:22:49 -0700
Subject: [PATCH 17/28] work

---
 test/lit/passes/print-boundary.wast | 63 +++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 test/lit/passes/print-boundary.wast

diff --git a/test/lit/passes/print-boundary.wast b/test/lit/passes/print-boundary.wast
new file mode 100644
index 00000000000..b1caf0b4801
--- /dev/null
+++ b/test/lit/passes/print-boundary.wast
@@ -0,0 +1,63 @@
+(module
+  (type $struct (struct))
+
+  (import "module" "base" (func $foo (param i32) (param f64) (result anyref)))
+
+  (import "module2" "other" (func $bar (result i32 f32)))
+
+  (export "one" (func $one))
+
+  (func $one (param $x (ref $struct)) (result i32 i32 i32)
+    (unreachable)
+  )
+)
+
+;; RUN: wasm-opt %s -all --print-boundary -S -o - | filecheck
+
+;; CHECK: [
+;; CHECK-NEXT:  [
+;; CHECK-NEXT:   {
+;; CHECK-NEXT:    "module": "module",
+;; CHECK-NEXT:    "base": "base",
+;; CHECK-NEXT:    "kind": 0,
+;; CHECK-NEXT:    "type": {
+;; CHECK-NEXT:     "params": [
+;; CHECK-NEXT:      "i32",
+;; CHECK-NEXT:      "f64"
+;; CHECK-NEXT:     ],
+;; CHECK-NEXT:     "results": [
+;; CHECK-NEXT:      "anyref"
+;; CHECK-NEXT:     ]
+;; CHECK-NEXT:    }
+;; CHECK-NEXT:   },
+;; CHECK-NEXT:   {
+;; CHECK-NEXT:    "module": "module2",
+;; CHECK-NEXT:    "base": "other",
+;; CHECK-NEXT:    "kind": 0,
+;; CHECK-NEXT:    "type": {
+;; CHECK-NEXT:     "params": [
+;; CHECK-NEXT:     ],
+;; CHECK-NEXT:     "results": [
+;; CHECK-NEXT:      "i32",
+;; CHECK-NEXT:      "f32"
+;; CHECK-NEXT:     ]
+;; CHECK-NEXT:    }
+;; CHECK-NEXT:   }
+;; CHECK-NEXT:  ],
+;; CHECK-NEXT:  [
+;; CHECK-NEXT:   {
+;; CHECK-NEXT:    "name": "one",
+;; CHECK-NEXT:    "kind": "func",
+;; CHECK-NEXT:    "type": {
+;; CHECK-NEXT:     "params": [
+;; CHECK-NEXT:      "(ref $struct.0)"
+;; CHECK-NEXT:     ],
+;; CHECK-NEXT:     "results": [
+;; CHECK-NEXT:      "i32",
+;; CHECK-NEXT:      "i32",
+;; CHECK-NEXT:      "i32"
+;; CHECK-NEXT:     ]
+;; CHECK-NEXT:    }
+;; CHECK-NEXT:   }
+;; CHECK-NEXT:  ]
+;; CHECK-NEXT: ]

From 71ce04be636c7e1cb0421fe14fc48c7fd83af2b0 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Tue, 12 May 2026 16:23:20 -0700
Subject: [PATCH 18/28] work

---
 test/lit/passes/print-boundary.wast | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/lit/passes/print-boundary.wast b/test/lit/passes/print-boundary.wast
index b1caf0b4801..300d64d34b6 100644
--- a/test/lit/passes/print-boundary.wast
+++ b/test/lit/passes/print-boundary.wast
@@ -12,7 +12,7 @@
   )
 )
 
-;; RUN: wasm-opt %s -all --print-boundary -S -o - | filecheck
+;; RUN: wasm-opt %s -all --print-boundary -S -o - | filecheck %s
 
 ;; CHECK: [
 ;; CHECK-NEXT:  [

From 4b500a200fc04211d6373fcd02933ae15b9549e8 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 14 May 2026 09:01:32 -0700
Subject: [PATCH 19/28] work

---
 src/support/json.cpp | 99 ++++++++++++++++++++++++++++++++++----------
 src/support/json.h   | 24 ++++++++++-
 test/gtest/json.cpp  | 57 ++++++++++++++++++++++++-
 3 files changed, 155 insertions(+), 25 deletions(-)

diff --git a/src/support/json.cpp b/src/support/json.cpp
index ff393317410..506f9cc475f 100644
--- a/src/support/json.cpp
+++ b/src/support/json.cpp
@@ -19,30 +19,85 @@
 
 namespace json {
 
-void Value::stringify(std::ostream& os, bool pretty) {
-  if (isString()) {
-    std::stringstream wtf16;
-    [[maybe_unused]] bool valid =
-      wasm::String::convertWTF8ToWTF16(wtf16, getIString().view());
-    assert(valid);
-    // TODO: Use wtf16.view() once we have C++20.
-    wasm::String::printEscapedJSON(os, wtf16.str());
-  } else if (isArray()) {
-    os << '[';
-    auto first = true;
-    for (auto& item : getArray()) {
-      if (first) {
-        first = false;
-      } else {
-        // TODO pretty whitespace
-        os << ',';
+void Value::stringify(std::ostream& os, bool pretty, int indent) {
+  auto doIndent = [&]() {
+    for (int i = 0; i < indent; i++) {
+      os << ' ';
+    }
+  };
+
+  switch (type) {
+    case String: {
+      std::stringstream wtf16;
+      [[maybe_unused]] bool valid =
+        wasm::String::convertWTF8ToWTF16(wtf16, getIString().view());
+      assert(valid);
+      // TODO: Use wtf16.view() once we have C++20.
+      wasm::String::printEscapedJSON(os, wtf16.str());
+      return;
+    }
+    case Array: {
+      os << '[';
+      indent++;
+      auto first = true;
+      for (auto& item : getArray()) {
+        if (first) {
+          first = false;
+        } else {
+          os << ',';
+        }
+        if (pretty) {
+          os << '\n';
+          doIndent();
+        }
+        item->stringify(os, pretty, indent);
+      }
+      indent--;
+      if (pretty) {
+        os << '\n';
+        doIndent();
+      }
+      os << ']';
+      return;
+    }
+    case Object: {
+      os << '{';
+      indent++;
+      auto first = true;
+      for (auto& [key, value] : getObject()) {
+        if (first) {
+          first = false;
+        } else {
+          os << ',';
+        }
+        if (pretty) {
+          os << '\n';
+          doIndent();
+        }
+        os << "\"" << key << "\":";
+        if (pretty) {
+          os << ' ';
+        }
+        value->stringify(os, pretty, indent);
+      }
+      indent--;
+      if (pretty) {
+        os << '\n';
+        doIndent();
       }
-      item->stringify(os, pretty);
+      os << '}';
+      return;
     }
-    os << ']';
-  } else {
-    WASM_UNREACHABLE("TODO: stringify all of JSON");
-  }
+    case Number:
+      os << getNumber();
+      return;
+    case Null:
+      os << "null";
+      return;
+    case Bool:
+      os << (getBool() ? "true" : "false");
+      return;
+  };
 }
 
 } // namespace json
diff --git a/src/support/json.h b/src/support/json.h
index 23d0749f045..98e46b063fd 100644
--- a/src/support/json.h
+++ b/src/support/json.h
@@ -37,6 +37,7 @@
 #include <unordered_set>
 #include <vector>
 
+#include "support/insert_ordered.h"
 #include "support/istring.h"
 #include "support/safe_integer.h"
 #include "support/string.h"
@@ -67,7 +68,18 @@ struct Value {
     Ref& operator[](IString x) { return (*this->get())[x]; }
   };
 
+  static Ref make() { return Ref(new Value); }
   template<typename T> static Ref make(T t) { return Ref(new Value(t)); }
+  static Ref makeArray() {
+    Ref ret(new Value);
+    ret->setArray();
+    return ret;
+  }
+  static Ref makeObject() {
+    Ref ret(new Value);
+    ret->setObject();
+    return ret;
+  }
 
   enum Type {
     String = 0,
@@ -81,7 +93,7 @@ struct Value {
   Type type = Null;
 
   using ArrayStorage = std::vector<Ref>;
-  using ObjectStorage = std::unordered_map<IString, Ref>;
+  using ObjectStorage = wasm::InsertOrderedMap<IString, Ref>;
 
   // MSVC does not allow unrestricted unions:
   // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2544.pdf
@@ -102,6 +114,10 @@ struct Value {
   // constructors all copy their input
   Value() {}
   explicit Value(const char* s) : type(Null) { setString(s); }
+  explicit Value(const std::string& s) : type(Null) { setString(s.c_str()); }
+  explicit Value(const std::string_view& s) : type(Null) {
+    setString(std::string(s));
+  }
   explicit Value(double n) : type(Null) { setNumber(n); }
   explicit Value(ArrayStorage& a) : type(Null) {
     setArray();
@@ -202,6 +218,10 @@ struct Value {
     assert(isArray());
     return *arr;
   }
+  ObjectStorage& getObject() {
+    assert(isObject());
+    return *obj;
+  }
   bool& getBool() {
     assert(isBool());
     return boo;
@@ -378,7 +398,7 @@ struct Value {
     return curr;
   }
 
-  void stringify(std::ostream& os, bool pretty = false);
+  void stringify(std::ostream& os, bool pretty = false, int indent = 0);
 
   // String operations
 
diff --git a/test/gtest/json.cpp b/test/gtest/json.cpp
index 626861a626a..5cd737ac6df 100644
--- a/test/gtest/json.cpp
+++ b/test/gtest/json.cpp
@@ -3,7 +3,7 @@
 
 using JSONTest = ::testing::Test;
 
-TEST_F(JSONTest, Stringify) {
+TEST_F(JSONTest, RoundtripString) {
   // TODO: change the API to not require a copy
   auto input = "[\"hello\",\"world\"]";
   auto* copy = strdup(input);
@@ -14,3 +14,58 @@ TEST_F(JSONTest, Stringify) {
   EXPECT_EQ(ss.str(), input);
   free(copy);
 }
+
+static void
+checkOutput(json::Value::Ref ref, std::string expected, bool pretty = false) {
+  std::stringstream ss;
+  ref->stringify(ss, pretty);
+  EXPECT_EQ(ss.str(), expected);
+}
+
+static void checkPrettyOutput(json::Value::Ref ref, std::string expected) {
+  checkOutput(ref, expected, true);
+}
+
+TEST_F(JSONTest, StringifyArray) {
+  auto array = json::Value::makeArray();
+  array->push_back(json::Value::make(42));
+  array->push_back(json::Value::make("1337"));
+  array->push_back(json::Value::make()); // null
+  checkOutput(array, "[42,\"1337\",null]");
+  checkPrettyOutput(array, R"([
+ 42,
+ "1337",
+ null
+])");
+}
+
+TEST_F(JSONTest, StringifyObject) {
+  auto object = json::Value::makeObject();
+  object["foo"] = json::Value::make(42);
+  object["bar"] = json::Value::make("1337");
+  checkOutput(object, "{\"foo\":42,\"bar\":\"1337\"}");
+  checkPrettyOutput(object, R"({
+ "foo": 42,
+ "bar": "1337"
+})");
+}
+
+TEST_F(JSONTest, StringifyNesting) {
+  auto array = json::Value::makeArray();
+  auto object = json::Value::makeObject();
+  auto array1 = json::Value::makeArray();
+  auto object1 = json::Value::makeObject();
+  array->push_back(object);
+  object["body"] = array1;
+  array1->push_back(object1);
+  object1["value"] = json::Value::make(42);
+  checkPrettyOutput(array, R"([
+ {
+  "body": [
+   {
+    "value": 42
+   }
+  ]
+ }
+])");
+}

From 7d01d8861183e9666e1a662f1d9dc3c5956f6a5a Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 14 May 2026 11:41:46 -0700
Subject: [PATCH 20/28] c++20

---
 src/support/json.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/support/json.cpp b/src/support/json.cpp
index 506f9cc475f..111ccd4e6eb 100644
--- a/src/support/json.cpp
+++ b/src/support/json.cpp
@@ -32,8 +32,7 @@ void Value::stringify(std::ostream& os, bool pretty, int indent) {
       [[maybe_unused]] bool valid =
         wasm::String::convertWTF8ToWTF16(wtf16, getIString().view());
       assert(valid);
-      // TODO: Use wtf16.view() once we have C++20.
-      wasm::String::printEscapedJSON(os, wtf16.str());
+      wasm::String::printEscapedJSON(os, wtf16.view());
       return;
     }
     case Array: {

From 43f58d2fb5d232dce73f940a31254b6d74ff232d Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 14 May 2026 11:42:00 -0700
Subject: [PATCH 21/28] maybeNewline helper

---
 src/support/json.cpp | 27 +++++++++++----------------
 1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/src/support/json.cpp b/src/support/json.cpp
index 111ccd4e6eb..94f3df082e7 100644
--- a/src/support/json.cpp
+++ b/src/support/json.cpp
@@ -26,6 +26,13 @@ void Value::stringify(std::ostream& os, bool pretty, int indent) {
     }
   };
 
+  auto maybeNewline = [&]() {
+    if (pretty) {
+      os << '\n';
+      doIndent();
+    }
+  };
+
   switch (type) {
     case String: {
       std::stringstream wtf16;
@@ -45,17 +52,11 @@ void Value::stringify(std::ostream& os, bool pretty, int indent) {
         } else {
           os << ',';
         }
-        if (pretty) {
-          os << '\n';
-          doIndent();
-        }
+        maybeNewline();
         item->stringify(os, pretty, indent);
       }
       indent--;
-      if (pretty) {
-        os << '\n';
-        doIndent();
-      }
+      maybeNewline();
       os << ']';
       return;
     }
@@ -69,10 +70,7 @@ void Value::stringify(std::ostream& os, bool pretty, int indent) {
         } else {
           os << ',';
         }
-        if (pretty) {
-          os << '\n';
-          doIndent();
-        }
+        maybeNewline();
         os << "\"" << key << "\":";
         if (pretty) {
           os << ' ';
@@ -80,10 +78,7 @@ void Value::stringify(std::ostream& os, bool pretty, int indent) {
         value->stringify(os, pretty, indent);
       }
       indent--;
-      if (pretty) {
-        os << '\n';
-        doIndent();
-      }
+      maybeNewline();
       os << '}';
       return;
     }

From 5d8f9e61404eb8faa858a5ee09462691228640e3 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 14 May 2026 13:03:46 -0700
Subject: [PATCH 22/28] help

---
 test/lit/help/wasm-metadce.test | 2 ++
 test/lit/help/wasm-opt.test     | 2 ++
 test/lit/help/wasm2js.test      | 2 ++
 3 files changed, 6 insertions(+)

diff --git a/test/lit/help/wasm-metadce.test b/test/lit/help/wasm-metadce.test
index 4d5f8e33b89..b35982035d0 100644
--- a/test/lit/help/wasm-metadce.test
+++ b/test/lit/help/wasm-metadce.test
@@ -362,6 +362,8 @@
 ;; CHECK-NEXT:
 ;; CHECK-NEXT:   --print                                       print in s-expression format
 ;; CHECK-NEXT:
+;; CHECK-NEXT:   --print-boundary                              print boundary in JSON format
+;; CHECK-NEXT:
 ;; CHECK-NEXT:   --print-call-graph                            print call graph
 ;; CHECK-NEXT:
 ;; CHECK-NEXT:   --print-features                              print options for enabled
diff --git a/test/lit/help/wasm-opt.test b/test/lit/help/wasm-opt.test
index 8566645db87..1565b9686b7 100644
--- a/test/lit/help/wasm-opt.test
+++ b/test/lit/help/wasm-opt.test
@@ -398,6 +398,8 @@
 ;; CHECK-NEXT:
 ;; CHECK-NEXT:   --print                                       print in s-expression format
 ;; CHECK-NEXT:
+;; CHECK-NEXT:   --print-boundary                              print boundary in JSON format
+;; CHECK-NEXT:
 ;; CHECK-NEXT:   --print-call-graph                            print call graph
 ;; CHECK-NEXT:
 ;; CHECK-NEXT:   --print-features                              print options for enabled
diff --git a/test/lit/help/wasm2js.test b/test/lit/help/wasm2js.test
index 88d6504b384..32a1f60ed3e 100644
--- a/test/lit/help/wasm2js.test
+++ b/test/lit/help/wasm2js.test
@@ -326,6 +326,8 @@
 ;; CHECK-NEXT:
 ;; CHECK-NEXT:   --print                                       print in s-expression format
 ;; CHECK-NEXT:
+;; CHECK-NEXT:   --print-boundary                              print boundary in JSON format
+;; CHECK-NEXT:
 ;; CHECK-NEXT:   --print-call-graph                            print call graph
 ;; CHECK-NEXT:
 ;; CHECK-NEXT:   --print-features                              print options for enabled

From 1fa90862265693563dd5b4a66b93b4a7bfbef596 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 14 May 2026 13:13:49 -0700
Subject: [PATCH 23/28] fix

---
 src/passes/PrintBoundary.cpp        | 48 ++++++++++++++++-------------
 test/lit/passes/print-boundary.wast | 15 +++++++--
 2 files changed, 39 insertions(+), 24 deletions(-)

diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
index 0c237736763..94f876d98ea 100644
--- a/src/passes/PrintBoundary.cpp
+++ b/src/passes/PrintBoundary.cpp
@@ -73,7 +73,7 @@ struct PrintBoundary : public Pass {
         auto item = json::Value::makeObject();
         item["module"] = json::Value::make(import->module.view());
         item["base"] = json::Value::make(import->base.view());
-        item["kind"] = json::Value::make(kind);
+        item["kind"] = getKindName(kind);
         item["type"] = getExternalType(kind, import->name, *module);
         imports->push_back(item);
       });
@@ -84,27 +84,7 @@ struct PrintBoundary : public Pass {
     for (auto& exp : module->exports) {
       auto item = json::Value::makeObject();
       item["name"] = json::Value::make(exp->name.view());
-      const char* kind = nullptr;
-      switch (exp->kind) {
-        case ExternalKind::Function:
-          kind = "func";
-          break;
-        case ExternalKind::Table:
-          kind = "table";
-          break;
-        case ExternalKind::Memory:
-          kind = "memory";
-          break;
-        case ExternalKind::Global:
-          kind = "global";
-          break;
-        case ExternalKind::Tag:
-          kind = "tag";
-          break;
-        case ExternalKind::Invalid:
-          WASM_UNREACHABLE("invalid ExternalKind");
-      }
-      item["kind"] = json::Value::make(kind);
+      item["kind"] = getKindName(exp->kind);
       item["type"] =
         getExternalType(exp->kind, *exp->getInternalName(), *module);
       exports->push_back(item);
@@ -161,6 +141,30 @@ struct PrintBoundary : public Pass {
     }
     return {};
   }
+
+  json::Value::Ref getKindName(ExternalKind kind) {
+    const char* name = nullptr;
+    switch (kind) {
+      case ExternalKind::Function:
+        name = "func";
+        break;
+      case ExternalKind::Table:
+        name = "table";
+        break;
+      case ExternalKind::Memory:
+        name = "memory";
+        break;
+      case ExternalKind::Global:
+        name = "global";
+        break;
+      case ExternalKind::Tag:
+        name = "tag";
+        break;
+      case ExternalKind::Invalid:
+        WASM_UNREACHABLE("invalid ExternalKind");
+    }
+    return json::Value::make(name);
+  }
 };
 
 Pass* createPrintBoundaryPass() { return new PrintBoundary(); }
diff --git a/test/lit/passes/print-boundary.wast b/test/lit/passes/print-boundary.wast
index 300d64d34b6..936b451e5da 100644
--- a/test/lit/passes/print-boundary.wast
+++ b/test/lit/passes/print-boundary.wast
@@ -5,8 +5,12 @@
 
   (import "module2" "other" (func $bar (result i32 f32)))
 
+  (global $g (mut i32) (i32.const 42))
+
   (export "one" (func $one))
 
+  (export "glob" (global $g))
+
   (func $one (param $x (ref $struct)) (result i32 i32 i32)
     (unreachable)
   )
@@ -19,7 +23,7 @@
 ;; CHECK-NEXT:   {
 ;; CHECK-NEXT:    "module": "module",
 ;; CHECK-NEXT:    "base": "base",
-;; CHECK-NEXT:    "kind": 0,
+;; CHECK-NEXT:    "kind": "func",
 ;; CHECK-NEXT:    "type": {
 ;; CHECK-NEXT:     "params": [
 ;; CHECK-NEXT:      "i32",
@@ -33,7 +37,7 @@
 ;; CHECK-NEXT:   {
 ;; CHECK-NEXT:    "module": "module2",
 ;; CHECK-NEXT:    "base": "other",
-;; CHECK-NEXT:    "kind": 0,
+;; CHECK-NEXT:    "kind": "func",
 ;; CHECK-NEXT:    "type": {
 ;; CHECK-NEXT:     "params": [
 ;; CHECK-NEXT:     ],
@@ -58,6 +62,13 @@
 ;; CHECK-NEXT:      "i32"
 ;; CHECK-NEXT:     ]
 ;; CHECK-NEXT:    }
+;; CHECK-NEXT:   },
+;; CHECK-NEXT:   {
+;; CHECK-NEXT:    "name": "glob",
+;; CHECK-NEXT:    "kind": "global",
+;; CHECK-NEXT:    "type": [
+;; CHECK-NEXT:     "i32"
+;; CHECK-NEXT:    ]
 ;; CHECK-NEXT:   }
 ;; CHECK-NEXT:  ]
 ;; CHECK-NEXT: ]

From 4046717ea24b42dec69769788d23d942ce71b28f Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 14 May 2026 13:16:02 -0700
Subject: [PATCH 24/28] nice

---
 src/passes/PrintBoundary.cpp        | 6 +++---
 test/lit/passes/print-boundary.wast | 8 ++++----
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
index 94f876d98ea..da7f8b8a08c 100644
--- a/src/passes/PrintBoundary.cpp
+++ b/src/passes/PrintBoundary.cpp
@@ -92,9 +92,9 @@ struct PrintBoundary : public Pass {
 
     // Emit the final structure
     json::Value root;
-    root.setArray();
-    root.push_back(imports);
-    root.push_back(exports);
+    root.setObject();
+    root["imports"] = imports;
+    root["exports"] = exports;
 
     Output output(target, Flags::BinaryOption::Text);
     root.stringify(output.getStream(), true /* pretty */);
diff --git a/test/lit/passes/print-boundary.wast b/test/lit/passes/print-boundary.wast
index 936b451e5da..6a1c27ada4f 100644
--- a/test/lit/passes/print-boundary.wast
+++ b/test/lit/passes/print-boundary.wast
@@ -18,8 +18,8 @@
 
 ;; RUN: wasm-opt %s -all --print-boundary -S -o - | filecheck %s
 
-;; CHECK: [
-;; CHECK-NEXT:  [
+;; CHECK: {
+;; CHECK-NEXT:  "imports":
 ;; CHECK-NEXT:   {
 ;; CHECK-NEXT:    "module": "module",
 ;; CHECK-NEXT:    "base": "base",
@@ -48,7 +48,7 @@
 ;; CHECK-NEXT:    }
 ;; CHECK-NEXT:   }
 ;; CHECK-NEXT:  ],
-;; CHECK-NEXT:  [
+;; CHECK-NEXT:  "exports": [
 ;; CHECK-NEXT:   {
 ;; CHECK-NEXT:    "name": "one",
 ;; CHECK-NEXT:    "kind": "func",
@@ -71,4 +71,4 @@
 ;; CHECK-NEXT:    ]
 ;; CHECK-NEXT:   }
 ;; CHECK-NEXT:  ]
-;; CHECK-NEXT: ]
+;; CHECK-NEXT: }

From 0bb32cb91827a3dac64d287c3a8b4dc7cae631e0 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 14 May 2026 13:16:12 -0700
Subject: [PATCH 25/28] nice

---
 test/lit/passes/print-boundary.wast | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/lit/passes/print-boundary.wast b/test/lit/passes/print-boundary.wast
index 6a1c27ada4f..120b5b39858 100644
--- a/test/lit/passes/print-boundary.wast
+++ b/test/lit/passes/print-boundary.wast
@@ -18,7 +18,7 @@
 
 ;; RUN: wasm-opt %s -all --print-boundary -S -o - | filecheck %s
 
-;; CHECK: {
+;; CHECK:      {
 ;; CHECK-NEXT:  "imports":
 ;; CHECK-NEXT:   {
 ;; CHECK-NEXT:    "module": "module",

From 9de1bf5626dd620943b9396c69e234f44bb96e03 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 14 May 2026 13:16:27 -0700
Subject: [PATCH 26/28] nice

---
 test/lit/passes/print-boundary.wast | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/lit/passes/print-boundary.wast b/test/lit/passes/print-boundary.wast
index 120b5b39858..f58d7c16345 100644
--- a/test/lit/passes/print-boundary.wast
+++ b/test/lit/passes/print-boundary.wast
@@ -19,7 +19,7 @@
 ;; RUN: wasm-opt %s -all --print-boundary -S -o - | filecheck %s
 
 ;; CHECK:      {
-;; CHECK-NEXT:  "imports":
+;; CHECK-NEXT:  "imports": [
 ;; CHECK-NEXT:   {
 ;; CHECK-NEXT:    "module": "module",
 ;; CHECK-NEXT:    "base": "base",

From 24308d4e7cd6436a649e51d63bedb15e68ce29a2 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Fri, 15 May 2026 09:45:44 -0700
Subject: [PATCH 27/28] polish API: avoid lists for globals etc.

---
 src/passes/PrintBoundary.cpp        | 14 +++++++++++---
 test/lit/passes/print-boundary.wast |  4 +---
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
index da7f8b8a08c..6469d5e8c3a 100644
--- a/src/passes/PrintBoundary.cpp
+++ b/src/passes/PrintBoundary.cpp
@@ -102,18 +102,26 @@ struct PrintBoundary : public Pass {
 
   // Emits an array of multivalue types. For a signature, emits params and
   // results.
-  json::Value::Ref getTypes(Type type) {
+  //
+  // We emit an array only when needed, unless forceArray is set.
+  json::Value::Ref getTypes(Type type, bool forceArray=false) {
     if (type.isRef()) {
       auto heapType = type.getHeapType();
       if (heapType.isSignature()) {
         auto sig = heapType.getSignature();
         auto ret = json::Value::makeObject();
-        ret["params"] = getTypes(sig.params);
-        ret["results"] = getTypes(sig.results);
+        // Always emit arrays for params and results.
+        ret["params"] = getTypes(sig.params, true);
+        ret["results"] = getTypes(sig.results, true);
         return ret;
       }
     }
 
+    // Simplify the output, avoiding an array for a single value.
+    if (!forceArray && type.size() == 1) {
+      return json::Value::make(type.toString());
+    }
+
     auto ret = json::Value::makeArray();
     for (auto t : type) {
       ret->push_back(json::Value::make(t.toString()));
diff --git a/test/lit/passes/print-boundary.wast b/test/lit/passes/print-boundary.wast
index f58d7c16345..850618f07b1 100644
--- a/test/lit/passes/print-boundary.wast
+++ b/test/lit/passes/print-boundary.wast
@@ -66,9 +66,7 @@
 ;; CHECK-NEXT:   {
 ;; CHECK-NEXT:    "name": "glob",
 ;; CHECK-NEXT:    "kind": "global",
-;; CHECK-NEXT:    "type": [
-;; CHECK-NEXT:     "i32"
-;; CHECK-NEXT:    ]
+;; CHECK-NEXT:    "type": "i32"
 ;; CHECK-NEXT:   }
 ;; CHECK-NEXT:  ]
 ;; CHECK-NEXT: }

From 03ea8b6d3332de68ba8e1cc1153d5495c5501bb2 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Fri, 15 May 2026 11:34:52 -0700
Subject: [PATCH 28/28] format

---
 src/passes/PrintBoundary.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/passes/PrintBoundary.cpp b/src/passes/PrintBoundary.cpp
index 6469d5e8c3a..371e642e2d8 100644
--- a/src/passes/PrintBoundary.cpp
+++ b/src/passes/PrintBoundary.cpp
@@ -104,7 +104,7 @@ struct PrintBoundary : public Pass {
   // results.
   //
   // We emit an array only when needed, unless forceArray is set.
-  json::Value::Ref getTypes(Type type, bool forceArray=false) {
+  json::Value::Ref getTypes(Type type, bool forceArray = false) {
     if (type.isRef()) {
       auto heapType = type.getHeapType();
       if (heapType.isSignature()) {