From 30af2477e1f9c8f80736219490807cb32887b72c Mon Sep 17 00:00:00 2001
From: Eric Proulx <playmaverick@gmail.com>
Date: Mon, 25 May 2026 10:34:50 +0200
Subject: [PATCH] Drop Enumerable from Grape::Exceptions::ValidationErrors

`Grape::Exceptions::ValidationErrors` mixed in `Enumerable` and exposed
a public `#each` that yielded `(attribute, error)` pairs. That surface
was undocumented (the README only covers `#errors`, `#full_messages`,
`#message`, and `rescue_from`), untested, and had a single in-class
consumer: `#full_messages` calling `map` on `self`.

Removed `include Enumerable` and `#each`. Rewrote `#full_messages` to
walk the `errors` hash directly via `flat_map`, which also documents
the actual data shape (`{ params => [validations] }`) at the call site.

UPGRADING entry added since this is a contract break, even if the
surface was undocumented.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 CHANGELOG.md                              |  1 +
 UPGRADING.md                              | 18 +++++++++++++++
 lib/grape/exceptions/validation_errors.rb | 28 ++++++++---------------
 3 files changed, 29 insertions(+), 18 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8c579e464..eb5a5f0f6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -45,6 +45,7 @@
 * [#2733](https://github.com/ruby-grape/grape/pull/2733): Drop the dead `active_support/core_ext/hash/reverse_merge` require; call `ActiveSupport::HashWithIndifferentAccess.new(...)` directly at call sites - [@ericproulx](https://github.com/ericproulx).
 * [#2734](https://github.com/ruby-grape/grape/pull/2734): Extract `options_route_enabled` from the Endpoint options Hash into a dedicated `attr_accessor` - [@ericproulx](https://github.com/ericproulx).
 * [#2736](https://github.com/ruby-grape/grape/pull/2736): Collapse `Endpoint#run_validators` rescue branches via `ValidationErrors` flatten; `ValidationErrors#initialize` keyword renamed `errors:` → `exceptions:` - [@ericproulx](https://github.com/ericproulx).
+* [#2747](https://github.com/ruby-grape/grape/pull/2747): Drop `Enumerable` from `Grape::Exceptions::ValidationErrors` and remove its public `#each`; rewrite `#full_messages` to walk `#errors` directly - [@ericproulx](https://github.com/ericproulx).
 * Your contribution here.
 
 #### Fixes
diff --git a/UPGRADING.md b/UPGRADING.md
index eb3ed9ed5..5d7873696 100644
--- a/UPGRADING.md
+++ b/UPGRADING.md
@@ -13,6 +13,24 @@ Grape::Exceptions::ValidationErrors.new(errors: [validation, validation_array_er
 
 # after
 Grape::Exceptions::ValidationErrors.new(exceptions: [validation, validation_array_errors], headers:)
+#### `Grape::Exceptions::ValidationErrors` no longer mixes in `Enumerable`
+
+`Grape::Exceptions::ValidationErrors` no longer includes `Enumerable` and no longer defines a public `#each`. The Enumerable surface (`#each`, `#map`, `#select`, `#to_a`, etc.) was undocumented and untested; the documented accessors — `#errors`, `#full_messages`, `#message`, `#as_json` — are unchanged.
+
+If a `rescue_from` block iterated over the exception instance, switch to `#errors`:
+
+```ruby
+# before
+rescue_from Grape::Exceptions::ValidationErrors do |e|
+  e.each { |attribute, error| ... }
+end
+
+# after
+rescue_from Grape::Exceptions::ValidationErrors do |e|
+  e.errors.each do |attributes, errs|
+    errs.each { |error| ... }
+  end
+end
 ```
 
 #### `auth`, `http_basic` and `http_digest` now take keyword arguments
diff --git a/lib/grape/exceptions/validation_errors.rb b/lib/grape/exceptions/validation_errors.rb
index 69006201b..9fad6f94c 100644
--- a/lib/grape/exceptions/validation_errors.rb
+++ b/lib/grape/exceptions/validation_errors.rb
@@ -3,8 +3,6 @@
 module Grape
   module Exceptions
     class ValidationErrors < Base
-      include Enumerable
-
       attr_reader :errors
 
       def initialize(exceptions: [], headers: {})
@@ -12,14 +10,6 @@ def initialize(exceptions: [], headers: {})
         super(message: full_messages.join(', '), status: 400, headers:)
       end
 
-      def each
-        errors.each_pair do |attribute, errors|
-          errors.each do |error|
-            yield attribute, error
-          end
-        end
-      end
-
       def as_json(**_opts)
         errors.map do |k, v|
           {
@@ -34,14 +24,16 @@ def to_json(*_opts)
       end
 
       def full_messages
-        messages = map do |attributes, error|
-          translate(
-            :format,
-            scope: 'grape.errors',
-            default: '%<attributes>s %<message>s',
-            attributes: translate_attributes(attributes),
-            message: error.message
-          )
+        messages = errors.flat_map do |attributes, errs|
+          errs.map do |error|
+            translate(
+              :format,
+              scope: 'grape.errors',
+              default: '%<attributes>s %<message>s',
+              attributes: translate_attributes(attributes),
+              message: error.message
+            )
+          end
         end
         messages.uniq!
         messages