From 9c13a6ce5ff1f83489d9df65a5c7745efe16c8a4 Mon Sep 17 00:00:00 2001
From: Alexander Momchilov <alexander.momchilov@shopify.com>
Date: Fri, 22 Jul 2022 16:16:04 -0400
Subject: [PATCH] [ruby/psych] Raise specific error when an anchor isn't
 defined

https://github.com/ruby/psych/commit/98fbd5247a
---
 ext/psych/lib/psych/exception.rb        | 7 +++++++
 ext/psych/lib/psych/visitors/to_ruby.rb | 2 +-
 test/psych/test_hash.rb                 | 2 +-
 test/psych/test_merge_keys.rb           | 2 +-
 4 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/ext/psych/lib/psych/exception.rb b/ext/psych/lib/psych/exception.rb
index 04a9a906a4..d7469a4b30 100644
--- a/ext/psych/lib/psych/exception.rb
+++ b/ext/psych/lib/psych/exception.rb
@@ -13,6 +13,13 @@ module Psych
     end
   end
 
+  # Subclasses `BadAlias` for backwards compatibility
+  class AnchorNotDefined < BadAlias
+    def initialize anchor_name
+      super "An alias referenced an unknown anchor: #{anchor_name}"
+    end
+  end
+
   class DisallowedClass < Exception
     def initialize action, klass_name
       super "Tried to #{action} unspecified class: #{klass_name}"
diff --git a/ext/psych/lib/psych/visitors/to_ruby.rb b/ext/psych/lib/psych/visitors/to_ruby.rb
index 0bf5198ccc..cce5daf3bb 100644
--- a/ext/psych/lib/psych/visitors/to_ruby.rb
+++ b/ext/psych/lib/psych/visitors/to_ruby.rb
@@ -323,7 +323,7 @@ module Psych
       end
 
       def visit_Psych_Nodes_Alias o
-        @st.fetch(o.anchor) { raise BadAlias, "Unknown alias: #{o.anchor}" }
+        @st.fetch(o.anchor) { raise AnchorNotDefined, o.anchor }
       end
 
       private
diff --git a/test/psych/test_hash.rb b/test/psych/test_hash.rb
index 88b520ebfc..31eba8580b 100644
--- a/test/psych/test_hash.rb
+++ b/test/psych/test_hash.rb
@@ -124,7 +124,7 @@ module Psych
     end
 
     def test_raises_if_anchor_not_defined
-      assert_raise(Psych::BadAlias) do
+      assert_raise(Psych::AnchorNotDefined) do
         Psych.unsafe_load(<<~eoyml)
           ---
           foo: &foo
diff --git a/test/psych/test_merge_keys.rb b/test/psych/test_merge_keys.rb
index 8d2fceabf5..2f55a1ed8e 100644
--- a/test/psych/test_merge_keys.rb
+++ b/test/psych/test_merge_keys.rb
@@ -117,7 +117,7 @@ development:
 bar:
   << : *foo
       eoyml
-      exp = assert_raise(Psych::BadAlias) { Psych.load(yaml, aliases: true) }
+      exp = assert_raise(Psych::AnchorNotDefined) { Psych.load(yaml, aliases: true) }
       assert_match 'foo', exp.message
     end