[ios, macos] Raise exceptions for empty expression stops dictionaries (#9539)

4 files changed, 89 insertions, 2 deletions

diff --git a/platform/darwin/src/NSExpression+MGLAdditions.mm b/platform/darwin/src/NSExpression+MGLAdditions.mm
index c82a7dc008..8db839c5da 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.mm
+++ b/platform/darwin/src/NSExpression+MGLAdditions.mm
@@ -1258,9 +1258,15 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
         NSArray *controlPoints = [self.arguments[curveTypeIndex + 1].collection mgl_jsonExpressionObject];
         [interpolationArray addObjectsFromArray:controlPoints];
     }
+
+    NSDictionary<NSNumber *, NSExpression *> *stops = self.arguments[curveTypeIndex + 2].constantValue;
+
+    if (stops.count == 0) {
+        [NSException raise:NSInvalidArgumentException format:@"‘stops‘ dictionary argument to ‘%@’ function must not be empty.", self.function];
+    }
+
     NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"interpolate", interpolationArray, nil];
     [expressionObject addObject:(isAftermarketFunction ? self.arguments.firstObject : self.operand).mgl_jsonExpressionObject];
-    NSDictionary<NSNumber *, NSExpression *> *stops = self.arguments[curveTypeIndex + 2].constantValue;
     for (NSNumber *key in [stops.allKeys sortedArrayUsingSelector:@selector(compare:)]) {
         [expressionObject addObject:key];
         [expressionObject addObject:[stops[key] mgl_jsonExpressionObject]];
@@ -1272,8 +1278,14 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
     BOOL isAftermarketFunction = [self.function isEqualToString:@"mgl_step:from:stops:"];
     NSUInteger minimumIndex = isAftermarketFunction ? 1 : 0;
     id minimum = self.arguments[minimumIndex].mgl_jsonExpressionObject;
-    NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"step", (isAftermarketFunction ? self.arguments.firstObject : self.operand).mgl_jsonExpressionObject, minimum, nil];
     NSDictionary<NSNumber *, NSExpression *> *stops = self.arguments[minimumIndex + 1].constantValue;
+
+    if (stops.count == 0) {
+        [NSException raise:NSInvalidArgumentException format:@"‘stops‘ dictionary argument to ‘%@’ function must not be empty.", self.function];
+    }
+
+    NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"step", (isAftermarketFunction ? self.arguments.firstObject : self.operand).mgl_jsonExpressionObject, minimum, nil];
+
     for (NSNumber *key in [stops.allKeys sortedArrayUsingSelector:@selector(compare:)]) {
         [expressionObject addObject:key];
         [expressionObject addObject:[stops[key] mgl_jsonExpressionObject]];
diff --git a/platform/darwin/test/MGLExpressionTests.mm b/platform/darwin/test/MGLExpressionTests.mm
index d54e961b00..9c75dedaa3 100644
--- a/platform/darwin/test/MGLExpressionTests.mm
+++ b/platform/darwin/test/MGLExpressionTests.mm
@@ -710,6 +710,16 @@ using namespace std::string_literals;
         XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
         XCTAssertEqualObjects([NSExpression expressionWithMGLJSONObject:jsonExpression], expression);
     }
+    {
+        NSDictionary *stops = @{};
+        NSExpression *expression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(x, 'cubic-bezier', { 0.42, 0, 0.58, 1 }, %@)", stops];
+        XCTAssertThrowsSpecificNamed(expression.mgl_jsonExpressionObject, NSException, NSInvalidArgumentException);
+    }
+    {
+        NSDictionary *stops = @{};
+        NSExpression *expression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, 11, %@)", stops];
+        XCTAssertThrowsSpecificNamed(expression.mgl_jsonExpressionObject, NSException, NSInvalidArgumentException);
+    }
 }
 
 - (void)testMatchExpressionObject {
diff --git a/platform/ios/Integration Tests/MGLStyleLayerIntegrationTests.m b/platform/ios/Integration Tests/MGLStyleLayerIntegrationTests.m
new file mode 100644
index 0000000000..015a58d2d2
--- /dev/null
+++ b/platform/ios/Integration Tests/MGLStyleLayerIntegrationTests.m
@@ -0,0 +1,61 @@
+#import "MGLMapViewIntegrationTest.h"
+
+@interface MGLStyleLayerIntegrationTests : MGLMapViewIntegrationTest
+@end
+
+@implementation MGLStyleLayerIntegrationTests
+
+- (MGLCircleStyleLayer*)setupCircleStyleLayer {
+    // Adapted from https://www.mapbox.com/ios-sdk/examples/dds-circle-layer/
+
+    // "mapbox://examples.2uf7qges" is a map ID referencing a tileset. For more
+    // more information, see mapbox.com/help/define-map-id/
+    MGLSource *source = [[MGLVectorTileSource alloc] initWithIdentifier:@"trees" configurationURL:[NSURL URLWithString:@"mapbox://examples.2uf7qges"]];
+    [self.mapView.style addSource:source];
+
+    MGLCircleStyleLayer *layer = [[MGLCircleStyleLayer alloc] initWithIdentifier: @"tree-style" source:source];
+
+    // The source name from the source's TileJSON metadata: mapbox.com/api-documentation/#retrieve-tilejson-metadata
+    layer.sourceLayerIdentifier = @"yoshino-trees-a0puw5";
+
+    return layer;
+}
+
+- (void)testForInterpolatingExpressionRenderCrashWithEmptyStops {
+    // Tests: https://github.com/mapbox/mapbox-gl-native/issues/9539
+    // Adapted from https://www.mapbox.com/ios-sdk/examples/dds-circle-layer/
+    self.mapView.centerCoordinate = CLLocationCoordinate2DMake(38.897,-77.039);
+    self.mapView.zoomLevel = 10.5;
+
+    MGLCircleStyleLayer *layer = [self setupCircleStyleLayer];
+
+    NSExpression *interpExpression = [NSExpression mgl_expressionForInterpolatingExpression:NSExpression.zoomLevelVariableExpression
+                                                                              withCurveType:MGLExpressionInterpolationModeLinear
+                                                                                 parameters:nil
+                                                                                      stops:[NSExpression expressionForConstantValue:@{}]];
+
+    XCTAssertThrowsSpecificNamed((layer.circleColor = interpExpression), NSException, NSInvalidArgumentException);
+
+    [self.mapView.style addLayer:layer];
+    [self waitForMapViewToBeRenderedWithTimeout:1.0];
+}
+
+- (void)testForSteppingExpressionRenderCrashWithEmptyStops {
+    // Tests: https://github.com/mapbox/mapbox-gl-native/issues/9539
+    // Adapted from https://www.mapbox.com/ios-sdk/examples/dds-circle-layer/
+    self.mapView.centerCoordinate = CLLocationCoordinate2DMake(38.897,-77.039);
+    self.mapView.zoomLevel = 10.5;
+
+    MGLCircleStyleLayer *layer = [self setupCircleStyleLayer];
+
+    NSExpression *steppingExpression = [NSExpression mgl_expressionForSteppingExpression:NSExpression.zoomLevelVariableExpression
+                                                                          fromExpression:[NSExpression expressionForConstantValue:[UIColor greenColor]]
+                                                                                   stops:[NSExpression expressionForConstantValue:@{}]];
+
+    XCTAssertThrowsSpecificNamed((layer.circleColor = steppingExpression), NSException, NSInvalidArgumentException);
+
+    [self.mapView.style addLayer:layer];
+    [self waitForMapViewToBeRenderedWithTimeout:1.0];
+}
+
+@end
diff --git a/platform/ios/ios.xcodeproj/project.pbxproj b/platform/ios/ios.xcodeproj/project.pbxproj
index a9413accf2..6892760f59 100644
--- a/platform/ios/ios.xcodeproj/project.pbxproj
+++ b/platform/ios/ios.xcodeproj/project.pbxproj
@@ -362,6 +362,7 @@
 		AC518E03201BB56000EBC820 /* MGLTelemetryConfig.m in Sources */ = {isa = PBXBuildFile; fileRef = AC518DFE201BB55A00EBC820 /* MGLTelemetryConfig.m */; };
 		AC518E04201BB56100EBC820 /* MGLTelemetryConfig.m in Sources */ = {isa = PBXBuildFile; fileRef = AC518DFE201BB55A00EBC820 /* MGLTelemetryConfig.m */; };
 		CA0C27942076CA19001CE5B7 /* MGLMapViewIntegrationTest.m in Sources */ = {isa = PBXBuildFile; fileRef = CA0C27932076CA19001CE5B7 /* MGLMapViewIntegrationTest.m */; };
+		CA4EB8C720863487006AB465 /* MGLStyleLayerIntegrationTests.m in Sources */ = {isa = PBXBuildFile; fileRef = CA4EB8C620863487006AB465 /* MGLStyleLayerIntegrationTests.m */; };
 		CA55CD41202C16AA00CE7095 /* MGLCameraChangeReason.h in Headers */ = {isa = PBXBuildFile; fileRef = CA55CD3E202C16AA00CE7095 /* MGLCameraChangeReason.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		CA55CD42202C16AA00CE7095 /* MGLCameraChangeReason.h in Headers */ = {isa = PBXBuildFile; fileRef = CA55CD3E202C16AA00CE7095 /* MGLCameraChangeReason.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		CAA69DA4206DCD0E007279CD /* Mapbox.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = DA4A26961CB6E795000B7809 /* Mapbox.framework */; };
@@ -993,6 +994,7 @@
 		AC518DFE201BB55A00EBC820 /* MGLTelemetryConfig.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = MGLTelemetryConfig.m; sourceTree = "<group>"; };
 		CA0C27932076CA19001CE5B7 /* MGLMapViewIntegrationTest.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = MGLMapViewIntegrationTest.m; sourceTree = "<group>"; };
 		CA0C27952076CA50001CE5B7 /* MGLMapViewIntegrationTest.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = MGLMapViewIntegrationTest.h; sourceTree = "<group>"; };
+		CA4EB8C620863487006AB465 /* MGLStyleLayerIntegrationTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = MGLStyleLayerIntegrationTests.m; sourceTree = "<group>"; };
 		CA55CD3E202C16AA00CE7095 /* MGLCameraChangeReason.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = MGLCameraChangeReason.h; sourceTree = "<group>"; };
 		DA00FC8C1D5EEB0D009AABC8 /* MGLAttributionInfo.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = MGLAttributionInfo.h; sourceTree = "<group>"; };
 		DA00FC8D1D5EEB0D009AABC8 /* MGLAttributionInfo.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = MGLAttributionInfo.mm; sourceTree = "<group>"; };
@@ -1345,6 +1347,7 @@
 				16376B0B1FFD9DAF0000563E /* Info.plist */,
 				CA0C27932076CA19001CE5B7 /* MGLMapViewIntegrationTest.m */,
 				CA0C27952076CA50001CE5B7 /* MGLMapViewIntegrationTest.h */,
+				CA4EB8C620863487006AB465 /* MGLStyleLayerIntegrationTests.m */,
 			);
 			path = "Integration Tests";
 			sourceTree = "<group>";
@@ -2793,6 +2796,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				CA4EB8C720863487006AB465 /* MGLStyleLayerIntegrationTests.m in Sources */,
 				16376B0A1FFD9DAF0000563E /* MBGLIntegrationTests.m in Sources */,
 				CA0C27942076CA19001CE5B7 /* MGLMapViewIntegrationTest.m in Sources */,
 			);