Sync from Piper @317197168

PROTOBUF_SYNC_PIPER

Author: haberman

CHANGES.txt

@@ -11,16 +11,25 @@ Unreleased Changes
   * Added more Windows macros to proto whitelist.
   * Arena constructors for map entry messages are now marked "explicit"
     (for regular messages they were already explicit).
+  * Fix subtle aliasing bug in RepeatedField::Add
+  * Fix mismatch between MapEntry ByteSize and Serialize with respect to unset
+    fields.
 
   Python:
-  * Reject lowercase t for Timestamp json format. Fixes a conformance test.
+  * JSON format conformance fixes:
+    * Reject lowercase t for Timestamp json format.
+    * Print full_name directly for extensions (no camelCase).
+    * Reject boolean values for integer fields.
+    * Reject NaN, Infinity, -Infinity that is not quoted.
+    * Base64 fixes for bytes fields: accept URL-safe base64 and missing padding.
+  * Bugfix for fields/files named "async" or "await".
   * Improved the error message when AttributeError is returned from __getattr__
     in EnumTypeWrapper.
-  * Json format will print full_name directly for extensions.
 
   Java:
   * Fixed a bug where setting optional proto3 enums with setFooValue() would
     not mark the value as present.
+  * Add Subtract function to FieldMaskUtil.
 
   C#:
   * Dropped support for netstandard1.0 (replaced by support for netstandard1.1).

conformance/binary_json_conformance_suite.cc

@@ -3051,6 +3051,29 @@ void BinaryAndJsonConformanceSuite::RunJsonTestsForValue() {
           }
         ]
       )");
+  RunValidJsonTestWithValidator(
+      "NullValueInOtherOneofOldFormat", RECOMMENDED,
+      R"({"oneofNullValue": "NULL_VALUE"})",
+      [](const Json::Value& value) {
+        return (value.isMember("oneofNullValue") &&
+                value["oneofNullValue"].isNull());
+      },
+      true);
+  RunValidJsonTestWithValidator(
+      "NullValueInOtherOneofNewFormat", RECOMMENDED,
+      R"({"oneofNullValue": null})",
+      [](const Json::Value& value) {
+        return (value.isMember("oneofNullValue") &&
+                value["oneofNullValue"].isNull());
+      },
+      true);
+  RunValidJsonTestWithValidator(
+      "NullValueInNormalMessage", RECOMMENDED,
+      R"({"optionalNullValue": null})",
+      [](const Json::Value& value) {
+        return value.empty();
+      },
+      true);
 }
 
 void BinaryAndJsonConformanceSuite::RunJsonTestsForAny() {