Move creation of FSTFilter objects to static create method on FSTFilter. (#1512)

Rather than previously inlining it in the calling code. This is to unify
filter creation across platforms.

(This change involves altering FSTFilter from a protocol to an abstract
class.)

4 files changed, 16 insertions, 23 deletions

diff --git a/Firestore/Example/Tests/Core/FSTQueryTests.mm b/Firestore/Example/Tests/Core/FSTQueryTests.mm
index 6118d0f..362a94c 100644
--- a/Firestore/Example/Tests/Core/FSTQueryTests.mm
+++ b/Firestore/Example/Tests/Core/FSTQueryTests.mm
@@ -287,20 +287,19 @@ NS_ASSUME_NONNULL_BEGIN
   FSTQuery *baseQuery = FSTTestQuery("collection");
   FSTDocument *doc1 = FSTTestDoc("collection/doc", 0, @{ @"tags" : @[ @"foo", @1, @YES ] }, NO);
 
-  NSArray<id<FSTFilter>> *matchingFilters =
-      @[ FSTTestFilter("tags", @"==", @[ @"foo", @1, @YES ]) ];
+  NSArray<FSTFilter *> *matchingFilters = @[ FSTTestFilter("tags", @"==", @[ @"foo", @1, @YES ]) ];
 
-  NSArray<id<FSTFilter>> *nonMatchingFilters = @[
+  NSArray<FSTFilter *> *nonMatchingFilters = @[
     FSTTestFilter("tags", @"==", @"foo"),
     FSTTestFilter("tags", @"==", @[ @"foo", @1 ]),
     FSTTestFilter("tags", @"==", @[ @"foo", @YES, @1 ]),
   ];
 
-  for (id<FSTFilter> filter in matchingFilters) {
+  for (FSTFilter *filter in matchingFilters) {
     XCTAssertTrue([[baseQuery queryByAddingFilter:filter] matchesDocument:doc1]);
   }
 
-  for (id<FSTFilter> filter in nonMatchingFilters) {
+  for (FSTFilter *filter in nonMatchingFilters) {
     XCTAssertFalse([[baseQuery queryByAddingFilter:filter] matchesDocument:doc1]);
   }
 }
@@ -311,7 +310,7 @@ NS_ASSUME_NONNULL_BEGIN
       FSTTestDoc("collection/doc", 0,
                  @{ @"tags" : @{@"foo" : @"foo", @"a" : @0, @"b" : @YES, @"c" : @(NAN)} }, NO);
 
-  NSArray<id<FSTFilter>> *matchingFilters = @[
+  NSArray<FSTFilter *> *matchingFilters = @[
     FSTTestFilter("tags", @"==",
                   @{ @"foo" : @"foo",
                      @"a" : @0,
@@ -325,7 +324,7 @@ NS_ASSUME_NONNULL_BEGIN
     FSTTestFilter("tags.foo", @"==", @"foo")
   ];
 
-  NSArray<id<FSTFilter>> *nonMatchingFilters = @[
+  NSArray<FSTFilter *> *nonMatchingFilters = @[
     FSTTestFilter("tags", @"==", @"foo"), FSTTestFilter("tags", @"==", @{
       @"foo" : @"foo",
       @"a" : @0,
@@ -333,11 +332,11 @@ NS_ASSUME_NONNULL_BEGIN
     })
   ];
 
-  for (id<FSTFilter> filter in matchingFilters) {
+  for (FSTFilter *filter in matchingFilters) {
     XCTAssertTrue([[baseQuery queryByAddingFilter:filter] matchesDocument:doc1]);
   }
 
-  for (id<FSTFilter> filter in nonMatchingFilters) {
+  for (FSTFilter *filter in nonMatchingFilters) {
     XCTAssertFalse([[baseQuery queryByAddingFilter:filter] matchesDocument:doc1]);
   }
 }
diff --git a/Firestore/Example/Tests/Remote/FSTSerializerBetaTests.mm b/Firestore/Example/Tests/Remote/FSTSerializerBetaTests.mm
index da47aaa..51e99a8 100644
--- a/Firestore/Example/Tests/Remote/FSTSerializerBetaTests.mm
+++ b/Firestore/Example/Tests/Remote/FSTSerializerBetaTests.mm
@@ -476,7 +476,7 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 - (void)testEncodesRelationFilter {
-  FSTRelationFilter *input = FSTTestFilter("item.part.top", @"==", @"food");
+  FSTRelationFilter *input = (FSTRelationFilter *)FSTTestFilter("item.part.top", @"==", @"food");
   GCFSStructuredQuery_Filter *actual = [self.serializer encodedRelationFilter:input];
 
   GCFSStructuredQuery_Filter *expected = [GCFSStructuredQuery_Filter message];
@@ -488,7 +488,8 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 - (void)testEncodesArrayContainsFilter {
-  FSTRelationFilter *input = FSTTestFilter("item.tags", @"array_contains", @"food");
+  FSTRelationFilter *input =
+      (FSTRelationFilter *)FSTTestFilter("item.tags", @"array_contains", @"food");
   GCFSStructuredQuery_Filter *actual = [self.serializer encodedRelationFilter:input];
 
   GCFSStructuredQuery_Filter *expected = [GCFSStructuredQuery_Filter message];
diff --git a/Firestore/Example/Tests/Util/FSTHelpers.h b/Firestore/Example/Tests/Util/FSTHelpers.h
index 7946c06..8e5a86f 100644
--- a/Firestore/Example/Tests/Util/FSTHelpers.h
+++ b/Firestore/Example/Tests/Util/FSTHelpers.h
@@ -34,6 +34,7 @@
 @class FSTDocumentKeyReference;
 @class FSTDocumentSet;
 @class FSTFieldValue;
+@class FSTFilter;
 @class FSTLocalViewChanges;
 @class FSTPatchMutation;
 @class FSTQuery;
@@ -46,7 +47,6 @@
 @class FSTView;
 @class FSTViewSnapshot;
 @class FSTObjectValue;
-@protocol FSTFilter;
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -242,7 +242,7 @@ FSTQuery *FSTTestQuery(const absl::string_view path);
  * A convenience method to create a FSTFilter using a string representation for both field
  * and operator (<, <=, ==, >=, >, array_contains).
  */
-id<FSTFilter> FSTTestFilter(const absl::string_view field, NSString *op, id value);
+FSTFilter *FSTTestFilter(const absl::string_view field, NSString *op, id value);
 
 /** A convenience method for creating sort orders. */
 FSTSortOrder *FSTTestOrderBy(const absl::string_view field, NSString *direction);
diff --git a/Firestore/Example/Tests/Util/FSTHelpers.mm b/Firestore/Example/Tests/Util/FSTHelpers.mm
index 8ece82f..58513b0 100644
--- a/Firestore/Example/Tests/Util/FSTHelpers.mm
+++ b/Firestore/Example/Tests/Util/FSTHelpers.mm
@@ -179,7 +179,7 @@ FSTQuery *FSTTestQuery(const absl::string_view path) {
   return [FSTQuery queryWithPath:testutil::Resource(path)];
 }
 
-id<FSTFilter> FSTTestFilter(const absl::string_view field, NSString *opString, id value) {
+FSTFilter *FSTTestFilter(const absl::string_view field, NSString *opString, id value) {
   const FieldPath path = testutil::Field(field);
   FSTRelationFilterOperator op;
   if ([opString isEqualToString:@"<"]) {
@@ -199,15 +199,8 @@ id<FSTFilter> FSTTestFilter(const absl::string_view field, NSString *opString, i
   }
 
   FSTFieldValue *data = FSTTestFieldValue(value);
-  if ([data isEqual:[FSTDoubleValue nanValue]]) {
-    HARD_ASSERT(op == FSTRelationFilterOperatorEqual, "Must use == with NAN.");
-    return [[FSTNanFilter alloc] initWithField:path];
-  } else if ([data isEqual:[FSTNullValue nullValue]]) {
-    HARD_ASSERT(op == FSTRelationFilterOperatorEqual, "Must use == with Null.");
-    return [[FSTNullFilter alloc] initWithField:path];
-  } else {
-    return [FSTRelationFilter filterWithField:path filterOperator:op value:data];
-  }
+
+  return [FSTFilter filterWithField:path filterOperator:op value:data];
 }
 
 FSTSortOrder *FSTTestOrderBy(const absl::string_view field, NSString *direction) {