Firestore `isEqual()` on Public Types (#569)

* add bone code for new isEqual and unit test for old isEqual

*   add bone code for `FIRCollectionReference`, `FIRDocumentSnapshot`, `FIRFieldValue`, `FIRQuerySnapshot`, `FIRSnapshotMetadata`;
*   change inconsistenciness of `FIRFieldPath.isEqual` implementation;
*   add unit test (and file) for `FIRDocumentReferenceTest.m`, `FIRFieldPathTest.m`, `FIRQueryTests.testEquals`; `FIRGeoPoint` already has test and Blob is internal type.

* Implement isEqual for FIRCollectionReference

adding the working code and unit test.

* implement isEqual for FIRSnapshotMetadata

* Implement isEqual for FIRDocumentSnapshot

* Implement isEqual for FIRQuerySnapshot

* (un)implement `isEqual` for `FIRFieldValue`

Since `FIRFieldValue` both types are singleton, we do not need override `isEqual`. Add test to test the default `NSObject` `isEqual` works just fine.

* fix style with `scripts/style.sh`

* Implement hash for those with overridden isEqual without hash yet.

* refactor to use test helper functions -- FSTTestFirestore, FSTTestPath, FSTTestDocKey

* refactor using test helper `FSTTestDocSnapshot`, `FSTTestFieldPath`, `FSTTestQuery`, `FSTTestDoc`

* refactoring to use test helper method `FSTTestQuerySnapshot`,

* remove unneccessary nil-check, check isKindOfClass instead of isEqual

* refactoring: adding `FSTAPIHelpers.{h,m}`, `FSTTest{Collection,Document}Ref`,  better naming and style fix

* a file forgot in last commit

* mainly clean up import and some minor refactoring

* fix style via style.sh

* minor style fix

* add pragma ignored -Wnonnull

7 files changed, 110 insertions, 3 deletions

diff --git a/Firestore/Source/API/FIRCollectionReference.mm b/Firestore/Source/API/FIRCollectionReference.mm
index 92cccc6..70a14c2 100644
--- a/Firestore/Source/API/FIRCollectionReference.mm
+++ b/Firestore/Source/API/FIRCollectionReference.mm
@@ -15,6 +15,7 @@
  */
 
 #import "FIRCollectionReference.h"
+#import "FIRFirestore.h"
 
 #include "Firestore/core/src/firebase/firestore/util/autoid.h"
 
@@ -65,6 +66,29 @@ NS_ASSUME_NONNULL_BEGIN
   FSTFail(@"Use FIRCollectionReference initWithPath: initializer.");
 }
 
+// NSObject Methods
+- (BOOL)isEqual:(nullable id)other {
+  if (other == self) return YES;
+  if (![[other class] isEqual:[self class]]) return NO;
+
+  return [self isEqualToReference:other];
+}
+
+- (BOOL)isEqualToReference:(nullable FIRCollectionReference *)reference {
+  if (self == reference) return YES;
+  if (reference == nil) return NO;
+  if (self.firestore != reference.firestore && ![self.firestore isEqual:reference.firestore])
+    return NO;
+  if (self.query != reference.query && ![self.query isEqual:reference.query]) return NO;
+  return YES;
+}
+
+- (NSUInteger)hash {
+  NSUInteger hash = [self.firestore hash];
+  hash = hash * 31u + [self.query hash];
+  return hash;
+}
+
 - (NSString *)collectionID {
   return [self.query.path lastSegment];
 }
diff --git a/Firestore/Source/API/FIRDocumentReference.m b/Firestore/Source/API/FIRDocumentReference.m
index 6279b7c..87e6631 100644
--- a/Firestore/Source/API/FIRDocumentReference.m
+++ b/Firestore/Source/API/FIRDocumentReference.m
@@ -116,7 +116,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (BOOL)isEqual:(nullable id)other {
   if (other == self) return YES;
-  if (!other || ![[other class] isEqual:[self class]]) return NO;
+  if (![[other class] isEqual:[self class]]) return NO;
 
   return [self isEqualToReference:other];
 }
diff --git a/Firestore/Source/API/FIRDocumentSnapshot.m b/Firestore/Source/API/FIRDocumentSnapshot.m
index 65c7b61..358ddac 100644
--- a/Firestore/Source/API/FIRDocumentSnapshot.m
+++ b/Firestore/Source/API/FIRDocumentSnapshot.m
@@ -78,6 +78,37 @@ NS_ASSUME_NONNULL_BEGIN
   return self;
 }
 
+// NSObject Methods
+- (BOOL)isEqual:(nullable id)other {
+  if (other == self) return YES;
+  // self class could be FIRDocumentSnapshot or subtype. So we compare with base type explicitly.
+  if (![other isKindOfClass:[FIRDocumentSnapshot class]]) return NO;
+
+  return [self isEqualToSnapshot:other];
+}
+
+- (BOOL)isEqualToSnapshot:(nullable FIRDocumentSnapshot *)snapshot {
+  if (self == snapshot) return YES;
+  if (snapshot == nil) return NO;
+  if (self.firestore != snapshot.firestore && ![self.firestore isEqual:snapshot.firestore])
+    return NO;
+  if (self.internalKey != snapshot.internalKey && ![self.internalKey isEqual:snapshot.internalKey])
+    return NO;
+  if (self.internalDocument != snapshot.internalDocument &&
+      ![self.internalDocument isEqual:snapshot.internalDocument])
+    return NO;
+  if (self.fromCache != snapshot.fromCache) return NO;
+  return YES;
+}
+
+- (NSUInteger)hash {
+  NSUInteger hash = [self.firestore hash];
+  hash = hash * 31u + [self.internalKey hash];
+  hash = hash * 31u + [self.internalDocument hash];
+  hash = hash * 31u + (self.fromCache ? 1 : 0);
+  return hash;
+}
+
 @dynamic exists;
 
 - (BOOL)exists {
diff --git a/Firestore/Source/API/FIRFieldPath.m b/Firestore/Source/API/FIRFieldPath.m
index d0a70c0..f4e532f 100644
--- a/Firestore/Source/API/FIRFieldPath.m
+++ b/Firestore/Source/API/FIRFieldPath.m
@@ -80,7 +80,7 @@ NS_ASSUME_NONNULL_BEGIN
   return [[[self class] alloc] initPrivate:self.internalValue];
 }
 
-- (BOOL)isEqual:(id)object {
+- (BOOL)isEqual:(nullable id)object {
   if (self == object) {
     return YES;
   }
diff --git a/Firestore/Source/API/FIRQuery.m b/Firestore/Source/API/FIRQuery.m
index bb1599a..2feca39 100644
--- a/Firestore/Source/API/FIRQuery.m
+++ b/Firestore/Source/API/FIRQuery.m
@@ -107,7 +107,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (BOOL)isEqual:(nullable id)other {
   if (other == self) return YES;
-  if (!other || ![[other class] isEqual:[self class]]) return NO;
+  if (![[other class] isEqual:[self class]]) return NO;
 
   return [self isEqualToQuery:other];
 }
diff --git a/Firestore/Source/API/FIRQuerySnapshot.m b/Firestore/Source/API/FIRQuerySnapshot.m
index 5e1af9a..177e461 100644
--- a/Firestore/Source/API/FIRQuerySnapshot.m
+++ b/Firestore/Source/API/FIRQuerySnapshot.m
@@ -16,6 +16,7 @@
 
 #import "Firestore/Source/API/FIRQuerySnapshot+Internal.h"
 
+#import "FIRFirestore.h"
 #import "FIRSnapshotMetadata.h"
 #import "Firestore/Source/API/FIRDocumentChange+Internal.h"
 #import "Firestore/Source/API/FIRDocumentSnapshot+Internal.h"
@@ -76,6 +77,35 @@ NS_ASSUME_NONNULL_BEGIN
   return self;
 }
 
+// NSObject Methods
+- (BOOL)isEqual:(nullable id)other {
+  if (other == self) return YES;
+  if (![[other class] isEqual:[self class]]) return NO;
+
+  return [self isEqualToSnapshot:other];
+}
+
+- (BOOL)isEqualToSnapshot:(nullable FIRQuerySnapshot *)snapshot {
+  if (self == snapshot) return YES;
+  if (snapshot == nil) return NO;
+  if (self.firestore != snapshot.firestore && ![self.firestore isEqual:snapshot.firestore])
+    return NO;
+  if (self.originalQuery != snapshot.originalQuery &&
+      ![self.originalQuery isEqual:snapshot.originalQuery])
+    return NO;
+  if (self.snapshot != snapshot.snapshot && ![self.snapshot isEqual:snapshot.snapshot]) return NO;
+  if (self.metadata != snapshot.metadata && ![self.metadata isEqual:snapshot.metadata]) return NO;
+  return YES;
+}
+
+- (NSUInteger)hash {
+  NSUInteger hash = [self.firestore hash];
+  hash = hash * 31u + [self.originalQuery hash];
+  hash = hash * 31u + [self.snapshot hash];
+  hash = hash * 31u + [self.metadata hash];
+  return hash;
+}
+
 @dynamic empty;
 
 - (FIRQuery *)query {
diff --git a/Firestore/Source/API/FIRSnapshotMetadata.m b/Firestore/Source/API/FIRSnapshotMetadata.m
index 224015f..d957a8d 100644
--- a/Firestore/Source/API/FIRSnapshotMetadata.m
+++ b/Firestore/Source/API/FIRSnapshotMetadata.m
@@ -44,6 +44,28 @@ NS_ASSUME_NONNULL_BEGIN
   return self;
 }
 
+// NSObject Methods
+- (BOOL)isEqual:(nullable id)other {
+  if (other == self) return YES;
+  if (![[other class] isEqual:[self class]]) return NO;
+
+  return [self isEqualToMetadata:other];
+}
+
+- (BOOL)isEqualToMetadata:(nullable FIRSnapshotMetadata *)metadata {
+  if (self == metadata) return YES;
+  if (metadata == nil) return NO;
+  if (self.pendingWrites != metadata.pendingWrites) return NO;
+  if (self.fromCache != metadata.fromCache) return NO;
+  return YES;
+}
+
+- (NSUInteger)hash {
+  NSUInteger hash = self.pendingWrites ? 1 : 0;
+  hash = hash * 31u + (self.fromCache ? 1 : 0);
+  return hash;
+}
+
 @end
 
 NS_ASSUME_NONNULL_END