From 1c44851225958dd1d07a69f4e7175ad6bba71797 Mon Sep 17 00:00:00 2001
From: Jean Boussier <jean.boussier@gmail.com>
Date: Tue, 5 Nov 2024 12:59:58 +0100
Subject: [PATCH] Raise JSON::GeneratorError instead of
 Encoding::UndefinedConversionError

Followup: https://github.com/ruby/json/pull/633

That's what was raised historically. You could argue that this new
exception is more precise, but I've encountered some real production
code that expected the old behavior and that was broken by this change.
---
 ext/json/ext/generator/generator.c |  4 ++++
 java/src/json/ext/Generator.java   | 20 +++++++++++++-------
 lib/json/pure/generator.rb         | 10 +++++++++-
 test/json/json_generator_test.rb   | 14 +++++++++++---
 4 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/ext/json/ext/generator/generator.c b/ext/json/ext/generator/generator.c
index 645500d0..80539af6 100644
--- a/ext/json/ext/generator/generator.c
+++ b/ext/json/ext/generator/generator.c
@@ -1036,6 +1036,10 @@ static VALUE generate_json_rescue(VALUE d, VALUE exc)
     struct generate_json_data *data = (struct generate_json_data *)d;
     fbuffer_free(data->buffer);
 
+    if (RBASIC_CLASS(exc) == rb_path2class("Encoding::UndefinedConversionError")) {
+        exc = rb_exc_new_str(eGeneratorError, rb_funcall(exc, rb_intern("message"), 0));
+    }
+
     rb_exc_raise(exc);
 
     return Qundef;
diff --git a/java/src/json/ext/Generator.java b/java/src/json/ext/Generator.java
index b149feb3..f76dcb38 100644
--- a/java/src/json/ext/Generator.java
+++ b/java/src/json/ext/Generator.java
@@ -17,6 +17,7 @@
 import org.jruby.runtime.ThreadContext;
 import org.jruby.runtime.builtin.IRubyObject;
 import org.jruby.util.ByteList;
+import org.jruby.exceptions.RaiseException;
 
 public final class Generator {
     private Generator() {
@@ -402,14 +403,19 @@ void generate(Session session, RubyString object, ByteList buffer) {
                 RuntimeInfo info = session.getInfo();
                 RubyString src;
 
-                if (object.encoding(session.getContext()) != info.utf8.get()) {
-                    src = (RubyString)object.encode(session.getContext(),
-                                                    info.utf8.get());
-                } else {
-                    src = object;
-                }
+                try {
+                    if (object.encoding(session.getContext()) != info.utf8.get()) {
+                        src = (RubyString)object.encode(session.getContext(),
+                                                        info.utf8.get());
+                    } else {
+                        src = object;
+                    }
 
-                session.getStringEncoder().encode(src.getByteList(), buffer);
+                    session.getStringEncoder().encode(src.getByteList(), buffer);
+                } catch (RaiseException re) {
+                  throw Utils.newException(session.getContext(), Utils.M_GENERATOR_ERROR,
+                   re.getMessage());
+                }
             }
         };
 
diff --git a/lib/json/pure/generator.rb b/lib/json/pure/generator.rb
index 21e76546..5b4c8325 100644
--- a/lib/json/pure/generator.rb
+++ b/lib/json/pure/generator.rb
@@ -354,7 +354,13 @@ def generate(obj)
         # Assumes !@ascii_only, !@script_safe
         private def fast_serialize_string(string, buf) # :nodoc:
           buf << '"'
-          string = string.encode(::Encoding::UTF_8) unless string.encoding == ::Encoding::UTF_8
+          unless string.encoding == ::Encoding::UTF_8
+            begin
+              string = string.encode(::Encoding::UTF_8)
+            rescue Encoding::UndefinedConversionError => error
+              raise GeneratorError, error.message
+            end
+          end
           raise GeneratorError, "source sequence is illegal/malformed utf-8" unless string.valid_encoding?
 
           if /["\\\x0-\x1f]/n.match?(string)
@@ -557,6 +563,8 @@ def to_json(state = nil, *args)
             else
               %("#{JSON.utf8_to_json(string, state.script_safe)}")
             end
+          rescue Encoding::UndefinedConversionError => error
+            raise ::JSON::GeneratorError, error.message
           end
 
           # Module that holds the extending methods if, the String module is
diff --git a/test/json/json_generator_test.rb b/test/json/json_generator_test.rb
index 112c03b2..3bc7eb80 100755
--- a/test/json/json_generator_test.rb
+++ b/test/json/json_generator_test.rb
@@ -477,12 +477,20 @@ def test_invalid_encoding_string
     end
     assert_includes error.message, "source sequence is illegal/malformed utf-8"
 
-    assert_raise(Encoding::UndefinedConversionError) do
+    assert_raise(JSON::GeneratorError) do
+      JSON.dump("\x82\xAC\xEF".b)
+    end
+
+    assert_raise(JSON::GeneratorError) do
       "\x82\xAC\xEF".b.to_json
     end
 
-    assert_raise(Encoding::UndefinedConversionError) do
-      JSON.dump("\x82\xAC\xEF".b)
+    assert_raise(JSON::GeneratorError) do
+      ["\x82\xAC\xEF".b].to_json
+    end
+
+    assert_raise(JSON::GeneratorError) do
+      { foo: "\x82\xAC\xEF".b }.to_json
     end
   end