[ios, darwin] Make MGLFeature.attributes non-nullable and add integration testupstream/alexshalamov_fix_for_13378

Enforce non-nullable semantics for MGLFeature.attributes, to avoid construction of invalid mbgl::Feature properties
from nil NSDictionary object and align with public SDK property definition.

Integration test "testShapeSourceWithLineDistanceMetrics" is added to verify that MGLFeature is correctly converted.

Fixes issue #13378

5 files changed, 69 insertions, 15 deletions

diff --git a/platform/darwin/src/MGLFeature.mm b/platform/darwin/src/MGLFeature.mm
index 3b6a2ee488..d24c807625 100644
--- a/platform/darwin/src/MGLFeature.mm
+++ b/platform/darwin/src/MGLFeature.mm
@@ -25,11 +25,12 @@
 @implementation MGLEmptyFeature
 
 @synthesize identifier;
-@synthesize attributes;
+@synthesize attributes = _attributes;
 
 MGL_DEFINE_FEATURE_INIT_WITH_CODER();
 MGL_DEFINE_FEATURE_ENCODE();
 MGL_DEFINE_FEATURE_IS_EQUAL();
+MGL_DEFINE_FEATURE_ATTRIBUTES_GETTER();
 
 - (id)attributeForKey:(NSString *)key {
     MGLLogDebug(@"Retrieving attributeForKey: %@", key);
@@ -60,11 +61,12 @@ MGL_DEFINE_FEATURE_IS_EQUAL();
 @implementation MGLPointFeature
 
 @synthesize identifier;
-@synthesize attributes;
+@synthesize attributes = _attributes;
 
 MGL_DEFINE_FEATURE_INIT_WITH_CODER();
 MGL_DEFINE_FEATURE_ENCODE();
 MGL_DEFINE_FEATURE_IS_EQUAL();
+MGL_DEFINE_FEATURE_ATTRIBUTES_GETTER();
 
 - (id)attributeForKey:(NSString *)key {
     MGLLogDebug(@"Retrieving attributeForKey: %@", key);
@@ -96,11 +98,12 @@ MGL_DEFINE_FEATURE_IS_EQUAL();
 @implementation MGLPolylineFeature
 
 @synthesize identifier;
-@synthesize attributes;
+@synthesize attributes = _attributes;
 
 MGL_DEFINE_FEATURE_INIT_WITH_CODER();
 MGL_DEFINE_FEATURE_ENCODE();
 MGL_DEFINE_FEATURE_IS_EQUAL();
+MGL_DEFINE_FEATURE_ATTRIBUTES_GETTER();
 
 - (id)attributeForKey:(NSString *)key {
     MGLLogDebug(@"Retrieving attributeForKey: %@", key);
@@ -133,11 +136,12 @@ MGL_DEFINE_FEATURE_IS_EQUAL();
 @implementation MGLPolygonFeature
 
 @synthesize identifier;
-@synthesize attributes;
+@synthesize attributes = _attributes;
 
 MGL_DEFINE_FEATURE_INIT_WITH_CODER();
 MGL_DEFINE_FEATURE_ENCODE();
 MGL_DEFINE_FEATURE_IS_EQUAL();
+MGL_DEFINE_FEATURE_ATTRIBUTES_GETTER();
 
 - (id)attributeForKey:(NSString *)key {
     MGLLogDebug(@"Retrieving attributeForKey: %@", key);
@@ -170,11 +174,12 @@ MGL_DEFINE_FEATURE_IS_EQUAL();
 @implementation MGLPointCollectionFeature
 
 @synthesize identifier;
-@synthesize attributes;
+@synthesize attributes = _attributes;
 
 MGL_DEFINE_FEATURE_INIT_WITH_CODER();
 MGL_DEFINE_FEATURE_ENCODE();
 MGL_DEFINE_FEATURE_IS_EQUAL();
+MGL_DEFINE_FEATURE_ATTRIBUTES_GETTER();
 
 - (id)attributeForKey:(NSString *)key {
     MGLLogDebug(@"Retrieving attributeForKey: %@", key);
@@ -197,11 +202,12 @@ MGL_DEFINE_FEATURE_IS_EQUAL();
 @implementation MGLMultiPolylineFeature
 
 @synthesize identifier;
-@synthesize attributes;
+@synthesize attributes = _attributes;
 
 MGL_DEFINE_FEATURE_INIT_WITH_CODER();
 MGL_DEFINE_FEATURE_ENCODE();
 MGL_DEFINE_FEATURE_IS_EQUAL();
+MGL_DEFINE_FEATURE_ATTRIBUTES_GETTER();
 
 - (id)attributeForKey:(NSString *)key {
     MGLLogDebug(@"Retrieving attributeForKey: %@", key);
@@ -234,11 +240,12 @@ MGL_DEFINE_FEATURE_IS_EQUAL();
 @implementation MGLMultiPolygonFeature
 
 @synthesize identifier;
-@synthesize attributes;
+@synthesize attributes = _attributes;
 
 MGL_DEFINE_FEATURE_INIT_WITH_CODER();
 MGL_DEFINE_FEATURE_ENCODE();
 MGL_DEFINE_FEATURE_IS_EQUAL();
+MGL_DEFINE_FEATURE_ATTRIBUTES_GETTER();
 
 - (id)attributeForKey:(NSString *)key {
     MGLLogDebug(@"Retrieving attributeForKey: %@", key);
@@ -271,7 +278,7 @@ MGL_DEFINE_FEATURE_IS_EQUAL();
 @implementation MGLShapeCollectionFeature
 
 @synthesize identifier;
-@synthesize attributes;
+@synthesize attributes = _attributes;
 
 @dynamic shapes;
 
@@ -282,6 +289,7 @@ MGL_DEFINE_FEATURE_IS_EQUAL();
 MGL_DEFINE_FEATURE_INIT_WITH_CODER();
 MGL_DEFINE_FEATURE_ENCODE();
 MGL_DEFINE_FEATURE_IS_EQUAL();
+MGL_DEFINE_FEATURE_ATTRIBUTES_GETTER();
 
 - (id)attributeForKey:(NSString *)key {
     return self.attributes[key];
@@ -463,7 +471,7 @@ mbgl::Feature mbglFeature(mbgl::Feature feature, id identifier, NSDictionary *at
 
 NSDictionary<NSString *, id> *NSDictionaryFeatureForGeometry(NSDictionary *geometry, NSDictionary *attributes, id identifier) {
     NSMutableDictionary *feature = [@{@"type": @"Feature",
-                                      @"properties": (attributes) ?: [NSNull null],
+                                      @"properties": attributes,
                                       @"geometry": geometry} mutableCopy];
     feature[@"id"] = identifier;
     return [feature copy];
diff --git a/platform/darwin/src/MGLFeature_Private.h b/platform/darwin/src/MGLFeature_Private.h
index d4074b53ed..9fb1f91820 100644
--- a/platform/darwin/src/MGLFeature_Private.h
+++ b/platform/darwin/src/MGLFeature_Private.h
@@ -31,7 +31,7 @@ MGLShape* MGLShapeFromGeoJSON(const mapbox::geojson::geojson &geojson);
  returns the feature object with converted `mbgl::FeatureIdentifier` and
  `mbgl::PropertyMap` properties.
  */
-mbgl::Feature mbglFeature(mbgl::Feature feature, id identifier, NSDictionary *attributes);
+mbgl::Feature mbglFeature(mbgl::Feature feature, id identifier, NSDictionary * attributes);
 
 /**
  Returns an `NSDictionary` representation of an `MGLFeature`.
@@ -45,7 +45,7 @@ NS_ASSUME_NONNULL_END
         if (self = [super initWithCoder:decoder]) { \
             NSSet<Class> *identifierClasses = [NSSet setWithArray:@[[NSString class], [NSNumber class]]]; \
             identifier = [decoder decodeObjectOfClasses:identifierClasses forKey:@"identifier"]; \
-            attributes = [decoder decodeObjectOfClass:[NSDictionary class] forKey:@"attributes"]; \
+            _attributes = [decoder decodeObjectOfClass:[NSDictionary class] forKey:@"attributes"]; \
         } \
         return self; \
     }
@@ -54,7 +54,7 @@ NS_ASSUME_NONNULL_END
     - (void)encodeWithCoder:(NSCoder *)coder { \
         [super encodeWithCoder:coder]; \
         [coder encodeObject:identifier forKey:@"identifier"]; \
-        [coder encodeObject:attributes forKey:@"attributes"]; \
+        [coder encodeObject:_attributes forKey:@"attributes"]; \
     }
 
 #define MGL_DEFINE_FEATURE_IS_EQUAL() \
@@ -67,3 +67,11 @@ NS_ASSUME_NONNULL_END
     - (NSUInteger)hash { \
         return [super hash] + [[self geoJSONDictionary] hash]; \
     }
+
+#define MGL_DEFINE_FEATURE_ATTRIBUTES_GETTER() \
+    - (NSDictionary *) attributes { \
+        if (!_attributes) { \
+            return @{}; \
+        } \
+        return _attributes; \
+    }
diff --git a/platform/darwin/test/MGLFeatureTests.mm b/platform/darwin/test/MGLFeatureTests.mm
index 3e8e47474b..67f2a9a45e 100644
--- a/platform/darwin/test/MGLFeatureTests.mm
+++ b/platform/darwin/test/MGLFeatureTests.mm
@@ -176,7 +176,7 @@
     // it has no "id" key (or value)
     XCTAssertNil(geoJSONFeature[@"id"]);
     // it has a null representation of the properties object
-    XCTAssertEqualObjects(geoJSONFeature[@"properties"], [NSNull null]);
+    XCTAssertEqualObjects(geoJSONFeature[@"properties"], @{});
 
     // when there is a string identifier
     pointFeature.identifier = @"string-id";
@@ -317,13 +317,13 @@
                                        @"geometries": @[
                                            @{ @"geometry": @{@"type": @"Point",
                                                              @"coordinates": @[@(pointCoordinate.longitude), @(pointCoordinate.latitude)]},
-                                              @"properties": [NSNull null],
+                                              @"properties": @{},
                                               @"type": @"Feature",
                                              },
                                             @{ @"geometry": @{@"type": @"LineString",
                                                               @"coordinates": @[@[@(coord1.longitude), @(coord1.latitude)],
                                                                                 @[@(coord2.longitude), @(coord2.latitude)]]},
-                                               @"properties": [NSNull null],
+                                               @"properties": @{},
                                                @"type": @"Feature",
                                             }
                                         ]
diff --git a/platform/ios/CHANGELOG.md b/platform/ios/CHANGELOG.md
index 0244248b78..e1449b663e 100644
--- a/platform/ios/CHANGELOG.md
+++ b/platform/ios/CHANGELOG.md
@@ -29,6 +29,7 @@ Mapbox welcomes participation and contributions from everyone. Please read [CONT
 * Renamed `-[MGLOfflineStorage putResourceWithUrl:data:modified:expires:etag:mustRevalidate:]` to `-[MGLOfflineStorage preloadData:forURL:modificationDate:expirationDate:eTag:mustRevalidate:]`. ([#13318](https://github.com/mapbox/mapbox-gl-native/pull/13318))
 * Added `MGLLoggingConfiguration` and `MGLLoggingBlockHandler` that handle error and fault events produced by the SDK. ([#13235](https://github.com/mapbox/mapbox-gl-native/pull/13235))
 * Fixed random crashes during app termination. ([#13367](https://github.com/mapbox/mapbox-gl-native/pull/13367))
+* Fixed a crash when specifying MGLShapeSourceOptionLineDistanceMetrics when creating an MGLShapeSource. ([#13543](https://github.com/mapbox/mapbox-gl-native/pull/13543))
 
 ## 4.6.0 - November 7, 2018
 
diff --git a/platform/ios/Integration Tests/MGLShapeSourceTests.m b/platform/ios/Integration Tests/MGLShapeSourceTests.m
index 088a9b011e..836118450e 100644
--- a/platform/ios/Integration Tests/MGLShapeSourceTests.m
+++ b/platform/ios/Integration Tests/MGLShapeSourceTests.m
@@ -122,5 +122,42 @@
     [self waitForExpectations:@[expectation] timeout:1.0];
 }
 
+- (void)testShapeSourceWithLineDistanceMetrics {
+    CLLocationCoordinate2D coordinates[] = {
+        CLLocationCoordinate2DMake(9.6315313, 52.4133574),
+        CLLocationCoordinate2DMake(24.9410248, 60.1733244)};
+
+    MGLPolylineFeature *polylineFeature = [MGLPolylineFeature polylineWithCoordinates:coordinates count:sizeof(coordinates)/sizeof(coordinates[0])];
+    NSDictionary *options = @{MGLShapeSourceOptionLineDistanceMetrics: @YES};
+    MGLShapeSource *source = [[MGLShapeSource alloc] initWithIdentifier:@"route" shape:polylineFeature options:options];
+    MGLLineStyleLayer *lineLayer = [[MGLLineStyleLayer alloc] initWithIdentifier:@"lineLayer" source:source];
+
+    [self.style addSource:source];
+    [self.style addLayer:lineLayer];
+    [self.mapView setCenterCoordinate:CLLocationCoordinate2DMake(9.6315313, 52.4133574) animated:YES];
+
+    XCTestExpectation *expectation = [self expectationWithDescription:@"regionDidChange expectation"];
+    expectation.expectedFulfillmentCount = 1;
+    expectation.assertForOverFulfill = YES;
+
+    __weak id weakself = self;
+    self.regionDidChange = ^(MGLMapView *mapView, MGLCameraChangeReason reason, BOOL animated) {
+
+        id strongSelf = weakself;
+        if (!strongSelf)
+            return;
+
+        NSArray *features = [source featuresMatchingPredicate:nil];
+        MGLTestAssert(strongSelf, features.count == 1UL, @"Should contain one Feature");
+
+        MGLPolylineFeature *feature = [features objectAtIndex:0];
+        MGLTestAssertNotNil(strongSelf, [feature.attributes objectForKey:@"mapbox_clip_start"], @"Attributes should contain mapbox_clip_start property");
+        MGLTestAssertNotNil(strongSelf, [feature.attributes objectForKey:@"mapbox_clip_end"], @"Attributes should contain mapbox_clip_end property");
+
+        [expectation fulfill];
+    };
+
+    [self waitForExpectations:@[expectation] timeout:1.0];
+}
 
 @end