Firestore: FIRQueryTests.mm: Add test testBloomFilterShouldCorrectlyE…

…ncodeComplexUnicodeCharacters (#11679)

Firestore/Example/Tests/Integration/API/FIRQueryTests.mm

@@ -1285,4 +1285,144 @@ - (void)testResumingAQueryShouldUseBloomFilterToAvoidFullRequery {
   }
 }
 
+- (void)testBloomFilterShouldCorrectlyEncodeComplexUnicodeCharacters {
+  // TODO(b/291365820): Stop skipping this test when running against the Firestore emulator once
+  // the emulator is improved to include a bloom filter in the existence filter messages that it
+  // sends.
+  XCTSkipIf([FSTIntegrationTestCase isRunningAgainstEmulator],
+            "Skip this test when running against the Firestore emulator because the emulator does "
+            "not include a bloom filter when it sends existence filter messages, making it "
+            "impossible for this test to verify the correctness of the bloom filter.");
+
+  // Set this test to stop when the first failure occurs because some test assertion failures make
+  // the rest of the test not applicable or will even crash.
+  [self setContinueAfterFailure:NO];
+
+  // Define a comparator that compares `NSString` objects in a way that orders canonically-
+  // equivalent, but distinct, strings in a consistent manner by using `NSForcedOrderingSearch`.
+  // Otherwise, the bare `[NSString compare:]` method considers canonically-equivalent, but
+  // distinct, strings as "equal" and orders them indeterminately.
+  NSComparator sortComparator = ^(NSString *string1, NSString *string2) {
+    return [string1 compare:string2 options:NSForcedOrderingSearch];
+  };
+
+  // Firestore does not do any Unicode normalization on the document IDs. Therefore, two document
+  // IDs that are canonically-equivalent (i.e. they visually appear identical) but are represented
+  // by a different sequence of Unicode code points are treated as distinct document IDs.
+  NSArray<NSString *> *testDocIds;
+  {
+    NSMutableArray<NSString *> *testDocIdsAccumulator = [[NSMutableArray alloc] init];
+    [testDocIdsAccumulator addObject:@"DocumentToDelete"];
+    // The next two strings both end with "e" with an accent: the first uses the dedicated Unicode
+    // code point for this character, while the second uses the standard lowercase "e" followed by
+    // the accent combining character.
+    [testDocIdsAccumulator addObject:@"LowercaseEWithAcuteAccent_\u00E9"];
+    [testDocIdsAccumulator addObject:@"LowercaseEWithAcuteAccent_\u0065\u0301"];
+    // The next two strings both end with an "e" with two different accents applied via the
+    // following two combining characters. The combining characters are specified in a different
+    // order and Firestore treats these document IDs as unique, despite the order of the combining
+    // characters being irrelevant.
+    [testDocIdsAccumulator addObject:@"LowercaseEWithMultipleAccents_\u0065\u0301\u0327"];
+    [testDocIdsAccumulator addObject:@"LowercaseEWithMultipleAccents_\u0065\u0327\u0301"];
+    // The next string contains a character outside the BMP (the "basic multilingual plane"); that
+    // is, its code point is greater than 0xFFFF. Since NSString stores text in sequences of 16-bit
+    // code units, using the UTF-16 encoding (according to
+    // https://www.objc.io/issues/9-strings/unicode) it is stored as a surrogate pair, two 16-bit
+    // code units U+D83D and U+DE00, to represent this character. Make sure that its presence is
+    // correctly tested in the bloom filter, which uses UTF-8 encoding.
+    [testDocIdsAccumulator addObject:@"Smiley_\U0001F600"];
+
+    testDocIds = [NSArray arrayWithArray:testDocIdsAccumulator];
+  }
+
+  // Verify assumptions about the equivalence of strings in `testDocIds`.
+  XCTAssertEqualObjects(testDocIds[1].decomposedStringWithCanonicalMapping,
+                        testDocIds[2].decomposedStringWithCanonicalMapping);
+  XCTAssertEqualObjects(testDocIds[3].decomposedStringWithCanonicalMapping,
+                        testDocIds[4].decomposedStringWithCanonicalMapping);
+  XCTAssertEqual([testDocIds[5] characterAtIndex:7], 0xD83D);
+  XCTAssertEqual([testDocIds[5] characterAtIndex:8], 0xDE00);
+
+  // Create the mapping from document ID to document data for the document IDs specified in
+  // `testDocIds`.
+  NSMutableDictionary<NSString *, NSDictionary<NSString *, id> *> *testDocs =
+      [[NSMutableDictionary alloc] init];
+  for (NSString *testDocId in testDocIds) {
+    [testDocs setValue:@{@"foo" : @42} forKey:testDocId];
+  }
+
+  // Create the documents whose names contain complex Unicode characters in a new collection.
+  FIRCollectionReference *collRef = [self collectionRefWithDocuments:testDocs];
+
+  // Run a query to populate the local cache with documents that have names with complex Unicode
+  // characters.
+  {
+    FIRQuerySnapshot *querySnapshot1 = [self readDocumentSetForRef:collRef
+                                                            source:FIRFirestoreSourceDefault];
+    XCTAssertEqualObjects(
+        [FIRQuerySnapshotGetIDs(querySnapshot1) sortedArrayUsingComparator:sortComparator],
+        [testDocIds sortedArrayUsingComparator:sortComparator],
+        @"querySnapshot1 has the wrong documents");
+  }
+
+  // Delete one of the documents so that the next call to collection.get() will experience an
+  // existence filter mismatch. Use a different Firestore instance to avoid affecting the local
+  // cache.
+  FIRDocumentReference *documentToDelete = [collRef documentWithPath:@"DocumentToDelete"];
+  {
+    FIRFirestore *db2 = [self firestore];
+    [self deleteDocumentRef:[db2 documentWithPath:documentToDelete.path]];
+  }
+
+  // Wait for 10 seconds, during which Watch will stop tracking the query and will send an
+  // existence filter rather than "delete" events when the query is resumed.
+  [NSThread sleepForTimeInterval:10.0f];
+
+  // Resume the query and save the resulting snapshot for verification. Use some internal testing
+  // hooks to "capture" the existence filter mismatches.
+  __block FIRQuerySnapshot *querySnapshot2;
+  NSArray<FSTTestingHooksExistenceFilterMismatchInfo *> *existenceFilterMismatches =
+      [FSTTestingHooks captureExistenceFilterMismatchesDuringBlock:^{
+        querySnapshot2 = [self readDocumentSetForRef:collRef source:FIRFirestoreSourceDefault];
+      }];
+
+  // Verify that the snapshot from the resumed query contains the expected documents; that is, that
+  // it contains the documents whose names contain complex Unicode characters and _not_ the document
+  // that was deleted.
+  {
+    NSMutableArray<NSString *> *querySnapshot2ExpectedDocumentIds =
+        [NSMutableArray arrayWithArray:testDocIds];
+    [querySnapshot2ExpectedDocumentIds removeObject:documentToDelete.documentID];
+    XCTAssertEqualObjects(
+        [FIRQuerySnapshotGetIDs(querySnapshot2) sortedArrayUsingComparator:sortComparator],
+        [querySnapshot2ExpectedDocumentIds sortedArrayUsingComparator:sortComparator],
+        @"querySnapshot2 has the wrong documents");
+  }
+
+  // Verify that Watch sent an existence filter with the correct counts.
+  XCTAssertEqual(existenceFilterMismatches.count, 1u,
+                 @"Watch should have sent exactly 1 existence filter");
+  FSTTestingHooksExistenceFilterMismatchInfo *existenceFilterMismatchInfo =
+      existenceFilterMismatches[0];
+  XCTAssertEqual(existenceFilterMismatchInfo.localCacheCount, (int)testDocIds.count);
+  XCTAssertEqual(existenceFilterMismatchInfo.existenceFilterCount, (int)testDocIds.count - 1);
+
+  // Verify that Watch sent a valid bloom filter.
+  FSTTestingHooksBloomFilter *bloomFilter = existenceFilterMismatchInfo.bloomFilter;
+  XCTAssertNotNil(bloomFilter, "Watch should have included a bloom filter in the existence filter");
+
+  // The bloom filter application should statistically be successful almost every time; the _only_
+  // time when it would _not_ be successful is if there is a false positive when testing for
+  // 'DocumentToDelete' in the bloom filter. So verify that the bloom filter application is
+  // successful, unless there was a false positive.
+  BOOL isFalsePositive = [bloomFilter mightContain:documentToDelete];
+  XCTAssertEqual(bloomFilter.applied, !isFalsePositive);
+
+  // Verify that the bloom filter contains the document paths with complex Unicode characters.
+  for (FIRDocumentSnapshot *documentSnapshot in querySnapshot2.documents) {
+    XCTAssertTrue([bloomFilter mightContain:documentSnapshot.reference],
+                  @"The bloom filter should contain %@", documentSnapshot.documentID);
+  }
+}
+
 @end

Firestore/Example/Tests/Util/FSTTestingHooks.h

@@ -47,6 +47,9 @@ NS_ASSUME_NONNULL_BEGIN
 /** The number of bits of padding in the last byte of the bloom filter. */
 @property(nonatomic, readonly) int padding;
 
+/** Returns whether the bloom filter contains the given document. */
+- (BOOL)mightContain:(FIRDocumentReference*)documentRef;
+
 @end  // @interface FSTTestingHooksBloomFilter
 
 #pragma mark - FSTTestingHooksExistenceFilterMismatchInfo

Firestore/Example/Tests/Util/FSTTestingHooks.mm

@@ -47,34 +47,63 @@ @interface FSTTestingHooksBloomFilter ()
 - (instancetype)initWithApplied:(BOOL)applied
                       hashCount:(int)hashCount
                    bitmapLength:(int)bitmapLength
-                        padding:(int)padding NS_DESIGNATED_INITIALIZER;
+                        padding:(int)padding
+                      projectId:(std::string)projectId
+                     databaseId:(std::string)databaseId
+                    bloomFilter:(absl::optional<BloomFilter>)bloomFilter NS_DESIGNATED_INITIALIZER;
 
-- (instancetype)initWithBloomFilterInfo:(const TestingHooks::BloomFilterInfo&)bloomFilterInfo;
+- (instancetype)initWithBloomFilterInfo:(const TestingHooks::BloomFilterInfo&)bloomFilterInfo
+                              projectId:(std::string)projectId
+                             databaseId:(std::string)databaseId;
 
 @end
 
 #pragma mark - FSTTestingHooksBloomFilter implementation
 
-@implementation FSTTestingHooksBloomFilter
+@implementation FSTTestingHooksBloomFilter {
+  std::string _projectId;
+  std::string _databaseId;
+  absl::optional<BloomFilter> _bloomFilter;
+}
 
 - (instancetype)initWithApplied:(BOOL)applied
                       hashCount:(int)hashCount
                    bitmapLength:(int)bitmapLength
-                        padding:(int)padding {
+                        padding:(int)padding
+                      projectId:(std::string)projectId
+                     databaseId:(std::string)databaseId
+                    bloomFilter:(absl::optional<BloomFilter>)bloomFilter {
   if (self = [super init]) {
     _applied = applied;
     _hashCount = hashCount;
     _bitmapLength = bitmapLength;
     _padding = padding;
+    _projectId = std::move(projectId);
+    _databaseId = std::move(databaseId);
+    _bloomFilter = std::move(bloomFilter);
   }
   return self;
 }
 
-- (instancetype)initWithBloomFilterInfo:(const TestingHooks::BloomFilterInfo&)bloomFilterInfo {
+- (instancetype)initWithBloomFilterInfo:(const TestingHooks::BloomFilterInfo&)bloomFilterInfo
+                              projectId:(std::string)projectId
+                             databaseId:(std::string)databaseId {
   return [self initWithApplied:bloomFilterInfo.applied
                      hashCount:bloomFilterInfo.hash_count
                   bitmapLength:bloomFilterInfo.bitmap_length
-                       padding:bloomFilterInfo.padding];
+                       padding:bloomFilterInfo.padding
+                     projectId:std::move(projectId)
+                    databaseId:std::move(databaseId)
+                   bloomFilter:bloomFilterInfo.bloom_filter];
+}
+
+- (BOOL)mightContain:(FIRDocumentReference*)documentRef {
+  if (!_bloomFilter.has_value()) {
+    return NO;
+  }
+  std::string document_path = StringFormat("projects/%s/databases/%s/documents/%s", _projectId,
+                                           _databaseId, MakeStringView(documentRef.path));
+  return _bloomFilter->MightContain(document_path);
 }
 
 @end
@@ -114,7 +143,9 @@ - (instancetype)initWithExistenceFilterMismatchInfo:
   FSTTestingHooksBloomFilter* bloomFilter;
   if (existenceFilterMismatchInfo.bloom_filter.has_value()) {
     bloomFilter = [[FSTTestingHooksBloomFilter alloc]
-        initWithBloomFilterInfo:existenceFilterMismatchInfo.bloom_filter.value()];
+        initWithBloomFilterInfo:existenceFilterMismatchInfo.bloom_filter.value()
+                      projectId:existenceFilterMismatchInfo.project_id
+                     databaseId:existenceFilterMismatchInfo.database_id];
   } else {
     bloomFilter = nil;
   }

Firestore/core/src/remote/remote_event.cc

@@ -216,21 +216,25 @@ namespace {
 
 TestingHooks::ExistenceFilterMismatchInfo
 create_existence_filter_mismatch_info_for_testing_hooks(
-    BloomFilterApplicationStatus status,
     int local_cache_count,
-    const ExistenceFilterWatchChange& existence_filter) {
-  absl::optional<TestingHooks::BloomFilterInfo> bloom_filter;
+    const ExistenceFilterWatchChange& existence_filter,
+    const DatabaseId& database_id,
+    absl::optional<BloomFilter> bloom_filter,
+    BloomFilterApplicationStatus status) {
+  absl::optional<TestingHooks::BloomFilterInfo> bloom_filter_info;
   if (existence_filter.filter().bloom_filter_parameters().has_value()) {
     const BloomFilterParameters& bloom_filter_parameters =
         existence_filter.filter().bloom_filter_parameters().value();
-    bloom_filter = {status == BloomFilterApplicationStatus::kSuccess,
-                    bloom_filter_parameters.hash_count,
-                    static_cast<int>(bloom_filter_parameters.bitmap.size()),
-                    bloom_filter_parameters.padding};
+    bloom_filter_info = {
+        status == BloomFilterApplicationStatus::kSuccess,
+        bloom_filter_parameters.hash_count,
+        static_cast<int>(bloom_filter_parameters.bitmap.size()),
+        bloom_filter_parameters.padding, std::move(bloom_filter)};
   }
 
   return {local_cache_count, existence_filter.filter().count(),
-          std::move(bloom_filter)};
+          database_id.project_id(), database_id.database_id(),
+          std::move(bloom_filter_info)};
 }
 
 }  // namespace
@@ -264,8 +268,13 @@ void WatchChangeAggregator::HandleExistenceFilter(
       int current_size = GetCurrentDocumentCountForTarget(target_id);
       if (current_size != expected_count) {
         // Apply bloom filter to identify and mark removed documents.
+        absl::optional<BloomFilter> bloom_filter =
+            ParseBloomFilter(existence_filter);
         BloomFilterApplicationStatus status =
-            ApplyBloomFilter(existence_filter, current_size);
+            bloom_filter.has_value()
+                ? ApplyBloomFilter(bloom_filter.value(), existence_filter,
+                                   current_size)
+                : BloomFilterApplicationStatus::kSkipped;
         if (status != BloomFilterApplicationStatus::kSuccess) {
           // If bloom filter application fails, we reset the mapping and
           // trigger re-run of the query.
@@ -279,18 +288,20 @@ void WatchChangeAggregator::HandleExistenceFilter(
 
         TestingHooks::GetInstance().NotifyOnExistenceFilterMismatch(
             create_existence_filter_mismatch_info_for_testing_hooks(
-                status, current_size, existence_filter));
+                current_size, existence_filter,
+                target_metadata_provider_->GetDatabaseId(),
+                std::move(bloom_filter), status));
       }
     }
   }
 }
 
-BloomFilterApplicationStatus WatchChangeAggregator::ApplyBloomFilter(
-    const ExistenceFilterWatchChange& existence_filter, int current_count) {
+absl::optional<BloomFilter> WatchChangeAggregator::ParseBloomFilter(
+    const ExistenceFilterWatchChange& existence_filter) {
   const absl::optional<BloomFilterParameters>& bloom_filter_parameters =
       existence_filter.filter().bloom_filter_parameters();
   if (!bloom_filter_parameters.has_value()) {
-    return BloomFilterApplicationStatus::kSkipped;
+    return absl::nullopt;
   }
 
   util::StatusOr<BloomFilter> maybe_bloom_filter =
@@ -300,23 +311,30 @@ BloomFilterApplicationStatus WatchChangeAggregator::ApplyBloomFilter(
   if (!maybe_bloom_filter.ok()) {
     LOG_WARN("Creating BloomFilter failed: %s",
              maybe_bloom_filter.status().error_message());
-    return BloomFilterApplicationStatus::kSkipped;
+    return absl::nullopt;
   }
 
   BloomFilter bloom_filter = std::move(maybe_bloom_filter).ValueOrDie();
 
   if (bloom_filter.bit_count() == 0) {
-    return BloomFilterApplicationStatus::kSkipped;
+    return absl::nullopt;
   }
 
+  return bloom_filter;
+}
+
+BloomFilterApplicationStatus WatchChangeAggregator::ApplyBloomFilter(
+    const BloomFilter& bloom_filter,
+    const ExistenceFilterWatchChange& existence_filter,
+    int current_count) {
+  int expected_count = existence_filter.filter().count();
+
   int removed_document_count =
       FilterRemovedDocuments(bloom_filter, existence_filter.target_id());
 
-  int expected_count = existence_filter.filter().count();
-  if (expected_count != (current_count - removed_document_count)) {
-    return BloomFilterApplicationStatus::kFalsePositive;
-  }
-  return BloomFilterApplicationStatus::kSuccess;
+  return (expected_count == (current_count - removed_document_count))
+             ? BloomFilterApplicationStatus::kSuccess
+             : BloomFilterApplicationStatus::kFalsePositive;
 }
 
 int WatchChangeAggregator::FilterRemovedDocuments(

Firestore/core/src/remote/remote_event.h

@@ -417,12 +417,21 @@ class WatchChangeAggregator {
   bool TargetContainsDocument(model::TargetId target_id,
                               const model::DocumentKey& key);
 
+  /**
+   * Parse the bloom filter from the "unchanged_names" field of an existence
+   * filter.
+   */
+  static absl::optional<BloomFilter> ParseBloomFilter(
+      const ExistenceFilterWatchChange& existence_filter);
+
   /**
    * Apply bloom filter to remove the deleted documents, and return the
    * application status.
    */
   BloomFilterApplicationStatus ApplyBloomFilter(
-      const ExistenceFilterWatchChange& existence_filter, int current_count);
+      const BloomFilter& bloom_filter,
+      const ExistenceFilterWatchChange& existence_filter,
+      int current_count);
 
   /**
    * Filter out removed documents based on bloom filter membership result and