gh-103: Make non-existent MAP keys error.

Author: python-processing-unit

docs/SPECIFICATION.html

@@ -356,6 +356,8 @@
 
 `MAP` indexing MUST use angle brackets (`<` and `>`) with a comma-separated list of keys. Each key MUST evaluate to a scalar value of type `INT`, `FLT`, or `STR`. Tensor values MUST NOT be permitted as keys. The number of keys supplied MAY vary between lookups.
 
+Looking up a key that does not exist MUST raise a runtime error.
+
 Intermediate nested maps MUST be created on-demand when assigning to deeper keys. Assigning a value of a different type to an existing key MUST raise a runtime error.
 
 When a `MAP` index expression is used in call position and the indexed value resolves to a `FUNC`, the interpreter MUST bind `SELF` for the duration of that call to the `MAP` value that supplied the function. If the `MAP` expression refers to a visible pointer alias to a `MAP` binding, `SELF` MUST alias the underlying binding so that mutations through `SELF` update the original map. Otherwise `SELF` MUST follow normal `MAP` value semantics, so calling through a non-pointer value mutates only the local copy.

src/interpreter.c

@@ -1854,7 +1854,14 @@ Value eval_expr(Interpreter* interp, Expr* expr, Env* env) {
                         int found = 0;
                         Value got = value_map_get(cur, ikv, &found);
                         value_free(ikv);
-                        if (!found) { value_free(cur); final_val = value_null(); break; }
+                        if (!found) {
+                            value_free(cur);
+                            interp->error = strdup("Map key not found");
+                            interp->error_line = ik->line;
+                            interp->error_col = ik->column;
+                            err = true;
+                            break;
+                        }
                         value_free(cur);
                         cur = got; // continue descending (got is a copy)
                         if (ii + 1 == idxs->count) final_val = value_copy(cur);
@@ -1925,8 +1932,13 @@ Value eval_expr(Interpreter* interp, Expr* expr, Env* env) {
                     int found = 0;
                     Value got = value_map_get(cur, key, &found);
                     value_free(key);
-                    // If not found, return null (missing key)
-                    if (!found) { value_free(cur); return value_null(); }
+                    if (!found) {
+                        value_free(cur);
+                        interp->error = strdup("Map key not found");
+                        interp->error_line = it->line;
+                        interp->error_col = it->column;
+                        return value_null();
+                    }
                     // If this is last index, return the found value
                     if (i + 1 == nidx) {
                         // free original map container if it was a copy

tests/test2.pre

@@ -223,19 +223,32 @@ ASSERT(EQ(m<"foo">, 0d5))
 ASSERT(EQ(m<"bar">, 0d10))
 ASSERT(EQ(m<"nested", "a">, 0d1))
 ASSERT(EQ(m<"nested", "b">, 0d2))
-! Missing key should return null/false
-ASSERT(NOT(m<"nope">))
+! Missing key should raise an error
+INT: map_missing_err = 0d0
+TRY{
+    m<"nope">
+}CATCH{
+    map_missing_err = 0d1
+}
+ASSERT(EQ(map_missing_err, 0d1))
 PRINT("Maps: PASS\n")
 
 ! Regression test for GH-61: ensure DEL works on map index targets
 PRINT("Testing DEL on map indexing (regression GH-61)...")
 MAP: reg = <"foo" = 0d1, "bar" = 0d2, "nested" = <"a" = 0d10>>
 ASSERT(EQ(reg<"foo">, 0d1))
 DEL(reg<"foo">)
-ASSERT(NOT(reg<"foo">))
+ASSERT(NOT(KEYIN("foo", reg)))
+INT: reg_missing_err = 0d0
+TRY{
+    reg<"foo">
+}CATCH{
+    reg_missing_err = 0d1
+}
+ASSERT(EQ(reg_missing_err, 0d1))
 ! Deleting nested key
 DEL(reg<"nested", "a">)
-ASSERT(NOT(reg<"nested", "a">))
+ASSERT(NOT(KEYIN("a", reg<"nested">)))
 DEL(reg)
 PRINT("DEL map-index: PASS\n")