Support -0.0 in Firestore

packages/firestore/CHANGELOG.md

@@ -1,4 +1,8 @@
 # Unreleased
+- [fixed] Fixed an issue where the number value `-0.0` would lose its sign when
+  stored in Firestore.
+
+# 1.10.0
 - [feature] Implemented `Timestamp.valueOf()` so that `Timestamp` objects can be
   compared for relative ordering using the JavaScript arithmetic comparison
   operators (#2632).

packages/firestore/src/remote/serializer.ts

@@ -438,6 +438,8 @@ export class JsonProtoSerializer {
           return { doubleValue: 'Infinity' } as {};
         } else if (doubleValue === -Infinity) {
           return { doubleValue: '-Infinity' } as {};
+        } else if (typeUtils.isNegativeZero(doubleValue)) {
+          return { doubleValue: '-0' } as {};
         }
       }
       return { doubleValue: val.value() };
@@ -487,6 +489,8 @@ export class JsonProtoSerializer {
           return fieldValue.DoubleValue.POSITIVE_INFINITY;
         } else if ((obj.doubleValue as {}) === '-Infinity') {
           return fieldValue.DoubleValue.NEGATIVE_INFINITY;
+        } else if ((obj.doubleValue as {}) === '-0') {
+          return new fieldValue.DoubleValue(-0);
         }
       }
 

packages/firestore/src/util/types.ts

@@ -27,6 +27,13 @@ export function isNullOrUndefined(value: unknown): boolean {
   return value === null || value === undefined;
 }
 
+/** Returns whether the value represents -0. */
+export function isNegativeZero(value: number) : boolean {
+  // Detect if the value is -0.0. Based on polyfill from
+  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is
+  return value === -0 && 1 / value === 1 / -0;
+}
+
 /**
  * Returns whether a value is an integer and in the safe integer range
  * @param value The value to test for being an integer and in the safe range
@@ -35,7 +42,8 @@ export function isSafeInteger(value: unknown): boolean {
   return (
     typeof value === 'number' &&
     Number.isInteger(value) &&
-    (value as number) <= Number.MAX_SAFE_INTEGER &&
-    (value as number) >= Number.MIN_SAFE_INTEGER
+    !isNegativeZero(value) &&
+    value <= Number.MAX_SAFE_INTEGER &&
+    value >= Number.MIN_SAFE_INTEGER
   );
 }

packages/firestore/test/integration/api/type.test.ts

@@ -47,6 +47,12 @@ apiDescribe('Firestore', (persistence: boolean) => {
     });
   });
 
+  it('can read and write number fields', () => {
+    return withTestDb(persistence, db => {
+      return expectRoundtrip(db, { a: 1, b: NaN, c: Infinity, d: -0.0 });
+    });
+  });
+
   it('can read and write array fields', () => {
     return withTestDb(persistence, db => {
       return expectRoundtrip(db, { array: [1, 'foo', { deep: true }, null] });

packages/firestore/test/util/equality_matcher.ts

@@ -34,20 +34,21 @@ export interface Equatable<T> {
  */
 
 function customDeepEqual(left: unknown, right: unknown): boolean {
-  /**
-   * START: Custom compare logic
-   */
   if (typeof left === 'object' && left && 'isEqual' in left) {
     return (left as Equatable<unknown>).isEqual(right);
   }
   if (typeof right === 'object' && right && 'isEqual' in right) {
     return (right as Equatable<unknown>).isEqual(left);
   }
-  /**
-   * END: Custom compare logic
-   */
   if (left === right) {
-    return true;
+    if (left === 0.0 && right === 0.0) {
+      // Firestore treats -0.0 and +0.0 as not equals, even though JavaScript
+      // treats them as equal by default. Implemented based on MDN's Object.is()
+      // polyfill.
+      return 1 / left === 1 / right;
+    } else {
+      return true;
+    }
   }
   if (
     typeof left === 'number' &&