Allow querying for arrays in IN queries (#4285)

Author: Brian Chen

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

@@ -330,14 +330,17 @@ - (void)testQueriesCanUseInFilters {
     @"c" : @{@"zip" : @98103},
     @"d" : @{@"zip" : @[ @98101 ]},
     @"e" : @{@"zip" : @[ @"98101", @{@"zip" : @98101} ]},
-    @"f" : @{@"zip" : @{@"code" : @500}}
+    @"f" : @{@"zip" : @{@"code" : @500}},
+    @"g" : @{@"zip" : @[ @98101, @98102 ]}
   };
   FIRCollectionReference *collection = [self collectionRefWithDocuments:testDocs];
 
-  // Search for zips matching [98101, 98103].
-  FIRQuerySnapshot *snapshot =
-      [self readDocumentSetForRef:[collection queryWhereField:@"zip" in:@[ @98101, @98103 ]]];
-  XCTAssertEqualObjects(FIRQuerySnapshotGetData(snapshot), (@[ testDocs[@"a"], testDocs[@"c"] ]));
+  // Search for zips matching 98101, 98103, and [98101, 98102].
+  FIRQuerySnapshot *snapshot = [self
+      readDocumentSetForRef:[collection queryWhereField:@"zip"
+                                                     in:@[ @98101, @98103, @[ @98101, @98102 ] ]]];
+  XCTAssertEqualObjects(FIRQuerySnapshotGetData(snapshot),
+                        (@[ testDocs[@"a"], testDocs[@"c"], testDocs[@"g"] ]));
 
   // With objects
   snapshot = [self readDocumentSetForRef:[collection queryWhereField:@"zip"

Firestore/Source/API/FIRQuery.mm

@@ -429,6 +429,10 @@ - (FieldValue)parsedQueryValue:(id)value {
   return [self.firestore.dataConverter parsedQueryValue:value];
 }
 
+- (FieldValue)parsedQueryValue:(id)value allowArrays:(bool)allowArrays {
+  return [self.firestore.dataConverter parsedQueryValue:value allowArrays:allowArrays];
+}
+
 - (QuerySnapshot::Listener)wrapQuerySnapshotBlock:(FIRQuerySnapshotBlock)block {
   class Converter : public EventListener<QuerySnapshot> {
    public:
@@ -462,7 +466,8 @@ - (FIRQuery *)queryWithFilterOperator:(Filter::Operator)filterOperator
 - (FIRQuery *)queryWithFilterOperator:(Filter::Operator)filterOperator
                                  path:(const FieldPath &)fieldPath
                                 value:(id)value {
-  FieldValue fieldValue = [self parsedQueryValue:value];
+  FieldValue fieldValue = [self parsedQueryValue:value
+                                     allowArrays:filterOperator == Filter::Operator::In];
   auto describer = [value] { return util::MakeString(NSStringFromClass([value class])); };
   return Wrap(_query.Filter(fieldPath, filterOperator, std::move(fieldValue), describer));
 }

Firestore/Source/API/FSTUserDataConverter.h

@@ -82,6 +82,14 @@ typedef id _Nullable (^FSTPreConverterBlock)(id _Nullable);
 /** Parse a "query value" (e.g. value in a where filter or a value in a cursor bound). */
 - (model::FieldValue)parsedQueryValue:(id)input;
 
+/**
+ * Parse a "query value" (e.g. value in a where filter or a value in a cursor bound).
+ *
+ * @param allowArrays Whether the query value is an array that may directly contain additional
+ * arrays (e.g.) the operand of an `in` query).
+ */
+- (model::FieldValue)parsedQueryValue:(id)input allowArrays:(bool)allowArrays;
+
 @end
 
 NS_ASSUME_NONNULL_END

Firestore/Source/API/FSTUserDataConverter.mm

@@ -225,7 +225,12 @@ - (ParsedUpdateData)parsedUpdateData:(id)input {
 }
 
 - (FieldValue)parsedQueryValue:(id)input {
-  ParseAccumulator accumulator{UserDataSource::Argument};
+  return [self parsedQueryValue:input allowArrays:false];
+}
+
+- (FieldValue)parsedQueryValue:(id)input allowArrays:(bool)allowArrays {
+  ParseAccumulator accumulator{allowArrays ? UserDataSource::ArrayArgument
+                                           : UserDataSource::Argument};
 
   absl::optional<FieldValue> parsed = [self parseData:input context:accumulator.RootContext()];
   HARD_ASSERT(parsed, "Parsed data should not be nil.");
@@ -266,7 +271,10 @@ - (FieldValue)parsedQueryValue:(id)input {
 
     if ([input isKindOfClass:[NSArray class]]) {
       // TODO(b/34871131): Include the path containing the array in the error message.
-      if (context.array_element()) {
+      // In the case of IN queries, the parsed data is an array (representing the set of values to
+      // be included for the IN query) that may directly contain additional arrays (each
+      // representing an individual field value), so we disable this validation.
+      if (context.array_element() && context.data_source() != UserDataSource::ArrayArgument) {
         ThrowInvalidArgument("Nested arrays are not supported");
       }
       return [self parseArray:(NSArray *)input context:std::move(context)];

Firestore/core/src/firebase/firestore/core/user_data.cc

@@ -161,6 +161,7 @@ bool ParseContext::write() const {
     case UserDataSource::Update:
       return true;
     case UserDataSource::Argument:
+    case UserDataSource::ArrayArgument:
       return false;
     default:
       ThrowInvalidArgument("Unexpected case for UserDataSource: %s",

Firestore/core/src/firebase/firestore/core/user_data.h

@@ -61,6 +61,11 @@ enum class UserDataSource {
    * false.
    */
   Argument,
+  /**
+   * Indicates that the source is an Argument that may directly contain nested
+   * arrays (e.g. the operand of a `in` query).
+   */
+  ArrayArgument
 };
 
 /**