Add JSON conformance test that a single value provided for a repeated field should parse fail.

This adds tests for both an object instead of an array for a repeated submessage field, and a number instead of an array for a repeated int32 field.

C++Proto fails both tests. Pure-PHP fails this test only for the numbers case.

PiperOrigin-RevId: 791266294

Author: protobuf-github-bot

conformance/binary_json_conformance_suite.cc

@@ -1981,8 +1981,6 @@ void BinaryAndJsonConformanceSuiteImpl<MessageType>::RunJsonTests() {
                    "{\"optionalString\":\"Hello, World!\"}",
                    "optional_string: 'Hello, World!'");
 
-  // NOTE: The spec for JSON support is still being sorted out, these may not
-  // all be correct.
   RunJsonTestsForFieldNameConvention();
   RunJsonTestsForNonRepeatedTypes();
   RunJsonTestsForRepeatedTypes();
@@ -2902,6 +2900,14 @@ void BinaryAndJsonConformanceSuiteImpl<
   ExpectParseFailureForJson(
       "RepeatedFieldWrongElementTypeExpectingMessagesGotString", REQUIRED,
       R"({"repeatedNestedMessage": [{"a": 1}, "2"]})");
+
+  // A singular field where a repeated field was expected is not allowed, even
+  // if it is the right type.
+  ExpectParseFailureForJson("SingleValueForRepeatedFieldInt32", REQUIRED,
+                            R"({"repeatedInt32": 1})");
+  ExpectParseFailureForJson("SingleValueForRepeatedFieldMessage", REQUIRED,
+                            R"({"repeatedNestedMessage": {"a": 1}})");
+
   // Trailing comma in the repeated field is not allowed.
   ExpectParseFailureForJson("RepeatedFieldTrailingComma", RECOMMENDED,
                             R"({"repeatedInt32": [1, 2, 3, 4,]})");

conformance/failure_list_cpp.txt

@@ -35,3 +35,5 @@ Recommended.*.FieldMaskTooManyUnderscore.JsonOutput
 Recommended.*.JsonInput.FieldMaskInvalidCharacter                                                                  # Should have failed to parse, but didn't.
 Required.*.TimestampProtoNanoTooLarge.JsonOutput                                                                   # Should have failed to serialize, but didn't.
 Required.*.TimestampProtoNegativeNanos.JsonOutput                                                                  # Should have failed to serialize, but didn't.
+Required.*.JsonInput.SingleValueForRepeatedFieldInt32                                                              # Should have failed to parse, but didn't.
+Required.*.JsonInput.SingleValueForRepeatedFieldMessage                                                            # Should have failed to parse, but didn't.

conformance/failure_list_php.txt

@@ -44,3 +44,4 @@ Required.*.DurationProtoNanosWrongSign.JsonOutput # Should have failed to serial
 Required.*.DurationProtoNanosWrongSignNegativeSecs.JsonOutput # Should have failed to serialize, but didn't.
 Required.*.TimestampProtoNanoTooLarge.JsonOutput # Should have failed to serialize, but didn't.
 Required.*.TimestampProtoNegativeNanos.JsonOutput # Should have failed to serialize, but didn't.
+Required.*.JsonInput.SingleValueForRepeatedFieldInt32 # Should have failed to parse, but didn't.