Serialize Timestamps as string (per proto3 JSON format). (#2249)

* Serialize Timestamps as string (per proto3 JSON format).

* [AUTOMATED]: Prettier Code Styling

* Add an extra test for string format.

* Update changelog.

Author: yuchenshi

packages/firestore/CHANGELOG.md

@@ -2,6 +2,8 @@
 - [fixed] Fixed a regression that caused queries with nested field filters to
   crash the client if the field was not present in the local copy of the
   document. 
+- [fixed] Fixed an issue that caused requests with timestamps to Firestore
+  Emulator to fail.
 
 # 1.5.0
 - [feature] Added a `Firestore.waitForPendingWrites()` method that

packages/firestore/src/remote/serializer.ts

@@ -207,11 +207,24 @@ export class JsonProtoSerializer {
    * to actually return a Timestamp proto.
    */
   private toTimestamp(timestamp: Timestamp): string {
-    return {
-      seconds: '' + timestamp.seconds,
-      nanos: timestamp.nanoseconds
-      // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    } as any;
+    if (this.options.useProto3Json) {
+      // Serialize to ISO-8601 date format, but with full nano resolution.
+      // Since JS Date has only millis, let's only use it for the seconds and
+      // then manually add the fractions to the end.
+      const jsDateStr = new Date(timestamp.seconds * 1000).toISOString();
+      // Remove .xxx frac part and Z in the end.
+      const strUntilSeconds = jsDateStr.replace(/\.\d*/, '').replace('Z', '');
+      // Pad the fraction out to 9 digits (nanos).
+      const nanoStr = ('000000000' + timestamp.nanoseconds).slice(-9);
+
+      return `${strUntilSeconds}.${nanoStr}Z`;
+    } else {
+      return {
+        seconds: '' + timestamp.seconds,
+        nanos: timestamp.nanoseconds
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      } as any;
+    }
   }
 
   private fromTimestamp(date: string | TimestampProto): Timestamp {

packages/firestore/test/unit/remote/node/serializer.test.ts

@@ -300,6 +300,38 @@ describe('Serializer', () => {
       );
     });
 
+    it('converts TimestampValue to string (useProto3Json=true)', () => {
+      expect(
+        proto3JsonSerializer.toValue(
+          new fieldValue.TimestampValue(new Timestamp(1488872578, 916123456))
+        )
+      ).to.deep.equal({ timestampValue: '2017-03-07T07:42:58.916123456Z' });
+
+      expect(
+        proto3JsonSerializer.toValue(
+          new fieldValue.TimestampValue(new Timestamp(1488872578, 916123000))
+        )
+      ).to.deep.equal({ timestampValue: '2017-03-07T07:42:58.916123000Z' });
+
+      expect(
+        proto3JsonSerializer.toValue(
+          new fieldValue.TimestampValue(new Timestamp(1488872578, 916000000))
+        )
+      ).to.deep.equal({ timestampValue: '2017-03-07T07:42:58.916000000Z' });
+
+      expect(
+        proto3JsonSerializer.toValue(
+          new fieldValue.TimestampValue(new Timestamp(1488872578, 916000))
+        )
+      ).to.deep.equal({ timestampValue: '2017-03-07T07:42:58.000916000Z' });
+
+      expect(
+        proto3JsonSerializer.toValue(
+          new fieldValue.TimestampValue(new Timestamp(1488872578, 0))
+        )
+      ).to.deep.equal({ timestampValue: '2017-03-07T07:42:58.000000000Z' });
+    });
+
     it('converts GeoPointValue', () => {
       const example = new GeoPoint(1.23, 4.56);
       const expected = {