Raise JSON::GeneratorError instead of Encoding::UndefinedConversionError

Followup: ruby#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.

Author: byroot

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;

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());
+                }
             }
         };
 

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

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