[ios, macos] Raise NSException if layer or source added more than once

When MGLSource and MGLLayer instances are added to the style, they lose
ownership of their std::unique_ptr<T> after it is moved to the mbgl
level. Subsequent attempts to add such instances result in a C++
exception.

This adds logic in the Darwin platform to raise a NSException if the
source and layer addToMapView methods are called more than once and the
pointer is invalid. In addition, the documentation in MGLStyle for
addSource: and addLayer: has been update to warn developers to avoid
adding the same instance twice and, for that matter, instances with the
same identifier.

1 files changed, 60 insertions, 1 deletions

diff --git a/platform/darwin/test/MGLStyleTests.mm b/platform/darwin/test/MGLStyleTests.mm
index 07e012edc6..6a6a4a827f 100644
--- a/platform/darwin/test/MGLStyleTests.mm
+++ b/platform/darwin/test/MGLStyleTests.mm
@@ -1,4 +1,16 @@
-#import "MGLStyle.h"
+#import "MGLMapView.h"
+#import "MGLStyle_Private.h"
+
+#import "MGLGeoJSONSource.h"
+#import "MGLRasterSource.h"
+#import "MGLVectorSource.h"
+
+#import "MGLBackgroundStyleLayer.h"
+#import "MGLCircleStyleLayer.h"
+#import "MGLFillStyleLayer.h"
+#import "MGLLineStyleLayer.h"
+#import "MGLRasterStyleLayer.h"
+#import "MGLSymbolStyleLayer.h"
 
 #import "NSBundle+MGLAdditions.h"
 
@@ -92,6 +104,53 @@
     }];
 }
 
+- (void)testAddingSourcesTwice {
+    MGLMapView *mapView = [[MGLMapView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
+    MGLStyle *style = [[MGLStyle alloc] initWithMapView:mapView];
+
+    MGLGeoJSONSource *geoJSONSource = [[MGLGeoJSONSource alloc] initWithIdentifier:@"geoJSONSource" features:@[] options:nil];
+    [style addSource:geoJSONSource];
+    XCTAssertThrowsSpecificNamed([style addSource:geoJSONSource], NSException, @"MGLRedundantSourceException");
+
+    MGLRasterSource *rasterSource = [[MGLRasterSource alloc] initWithIdentifier:@"rasterSource" URL:[NSURL new] tileSize:42];
+    [style addSource:rasterSource];
+    XCTAssertThrowsSpecificNamed([style addSource:rasterSource], NSException, @"MGLRedundantSourceException");
+
+    MGLVectorSource *vectorSource = [[MGLVectorSource alloc] initWithIdentifier:@"vectorSource" URL:[NSURL new]];
+    [style addSource:vectorSource];
+    XCTAssertThrowsSpecificNamed([style addSource:vectorSource], NSException, @"MGLRedundantSourceException");
+}
+
+- (void)testAddingLayersTwice {
+    MGLMapView *mapView = [[MGLMapView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
+    MGLStyle *style = [[MGLStyle alloc] initWithMapView:mapView];
+    MGLGeoJSONSource *source = [[MGLGeoJSONSource alloc] initWithIdentifier:@"geoJSONSource" features:@[] options:nil];
+
+    MGLBackgroundStyleLayer *backgroundLayer = [[MGLBackgroundStyleLayer alloc] initWithIdentifier:@"backgroundLayer"];
+    [style addLayer:backgroundLayer];
+    XCTAssertThrowsSpecificNamed([style addLayer:backgroundLayer], NSException, @"MGLRedundantLayerException");
+
+    MGLCircleStyleLayer *circleLayer = [[MGLCircleStyleLayer alloc] initWithIdentifier:@"circleLayer" source:source];
+    [style addLayer:circleLayer];
+    XCTAssertThrowsSpecificNamed([style addLayer:circleLayer], NSException, @"MGLRedundantLayerException");
+
+    MGLFillStyleLayer *fillLayer = [[MGLFillStyleLayer alloc] initWithIdentifier:@"fillLayer" source:source];
+    [style addLayer:fillLayer];
+    XCTAssertThrowsSpecificNamed([style addLayer:fillLayer], NSException, @"MGLRedundantLayerException");
+
+    MGLLineStyleLayer *lineLayer = [[MGLLineStyleLayer alloc] initWithIdentifier:@"lineLayer" source:source];
+    [style addLayer:lineLayer];
+    XCTAssertThrowsSpecificNamed([style addLayer:lineLayer], NSException, @"MGLRedundantLayerException");
+
+    MGLRasterStyleLayer *rasterLayer = [[MGLRasterStyleLayer alloc] initWithIdentifier:@"rasterLayer" source:source];
+    [style addLayer:rasterLayer];
+    XCTAssertThrowsSpecificNamed([style addLayer:rasterLayer], NSException, @"MGLRedundantLayerException");
+
+    MGLSymbolStyleLayer *symbolLayer = [[MGLSymbolStyleLayer alloc] initWithIdentifier:@"symbolLayer" source:source];
+    [style addLayer:symbolLayer];
+    XCTAssertThrowsSpecificNamed([style addLayer:symbolLayer], NSException, @"MGLRedundantLayerException");
+}
+
 - (NSString *)stringWithContentsOfStyleHeader {
     NSURL *styleHeaderURL = [[[NSBundle mgl_frameworkBundle].bundleURL
                               URLByAppendingPathComponent:@"Headers" isDirectory:YES]