[ios, macos] More MGLGeoJSONSource options

MGLGeoJSONSource can now be initialized with GeoJSON data. Replaced the data property with a geoJSONData property and added features and URL properties alongside it. Each property may be set or unset based on how the object was initialized.

Fixes #5965, fixes #5966.

platform/darwin/src/MGLGeoJSONSource.h

@@ -1,9 +1,60 @@
 #import "MGLSource.h"
 
+#import "MGLTypes.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+@protocol MGLFeature;
+
 @interface MGLGeoJSONSource : MGLSource
 
-@property (nonatomic, readonly, copy) NSString *data;
+/**
+ The contents of the source.
+ 
+ If the receiver was initialized using `-initWithSourceIdentifier:URL:`, this
+ property is set to `nil`. This property is unavailable until the receiver is
+ passed into `-[MGLStyle addSource]`.
+ */
+@property (nonatomic, readonly, nullable) NS_ARRAY_OF(id <MGLFeature>) *features;
 
+/**
+ A GeoJSON representation of the contents of the source.
+ 
+ Use the `features` property instead to get an object representation of the
+ contents. Alternatively, use NSJSONSerialization with the value of this
+ property to transform it into Foundation types.
+ 
+ If the receiver was initialized using `-initWithSourceIdentifier:URL:`, this
+ property is set to `nil`. This property is unavailable until the receiver is
+ passed into `-[MGLStyle addSource]`.
+ */
+@property (nonatomic, readonly, nullable, copy) NSData *geoJSONData;
+
+/**
+ The URL to the GeoJSON document that specifies the contents of the source.
+ 
+ If the receiver was initialized using `-initWithSourceIdentifier:geoJSONData:`,
+ this property is set to `nil`.
+ */
+@property (nonatomic, readonly, nullable) NSURL *URL;
+
+/**
+ Initializes a source with the given identifier and GeoJSON data.
+ 
+ @param sourceIdentifier A string that uniquely identifies the source.
+ @param geoJSONData An NSData object representing GeoJSON source code.
+ */
+- (instancetype)initWithSourceIdentifier:(NSString *)sourceIdentifier geoJSONData:(NSData *)data NS_DESIGNATED_INITIALIZER;
+
+/**
+ Initializes a source with the given identifier and URL.
+ 
+ @param sourceIdentifier A string that uniquely identifies the source.
+ @param URL An HTTP(S) URL, absolute file URL, or local file URL relative to the
+    current application’s resource bundle.
+ */
 - (instancetype)initWithSourceIdentifier:(NSString *)sourceIdentifier URL:(NSURL *)url NS_DESIGNATED_INITIALIZER;
 
 @end
+
+NS_ASSUME_NONNULL_END

platform/darwin/src/MGLGeoJSONSource.mm

@@ -1,26 +1,24 @@
 #import "MGLGeoJSONSource.h"
 
 #import "MGLSource_Private.h"
+#import "MGLFeature_Private.h"
+
+#import "NSURL+MGLAdditions.h"
 
 #include <mbgl/style/sources/geojson_source.hpp>
 
-@interface MGLGeoJSONSource ()
-
-@property (nonatomic, copy) NSURL *URL;
-
-@end
-
 @implementation MGLGeoJSONSource
 
-- (instancetype)initWithSourceIdentifier:(NSString *)sourceIdentifier URL:(NSURL *)url
-{
+- (instancetype)initWithSourceIdentifier:(NSString *)sourceIdentifier geoJSONData:(NSData *)data {
+    if (self = [super initWithSourceIdentifier:sourceIdentifier]) {
+        _geoJSONData = data;
+    }
+    return self;
+}
+
+- (instancetype)initWithSourceIdentifier:(NSString *)sourceIdentifier URL:(NSURL *)url {
     if (self = [super initWithSourceIdentifier:sourceIdentifier]) {
         _URL = url;
-        if (url.isFileURL) {
-            _data = [[NSString alloc] initWithContentsOfURL:url encoding:NSUTF8StringEncoding error:NULL];
-        } else {
-            _data = url.absoluteString;
-        }
     }
     return self;
 }
@@ -28,11 +26,14 @@
 - (std::unique_ptr<mbgl::style::Source>)mbgl_source
 {
     auto source = std::make_unique<mbgl::style::GeoJSONSource>(self.sourceIdentifier.UTF8String);
-    if (_URL.isFileURL) {
-        const auto geojson = mapbox::geojson::parse(self.data.UTF8String).get<mapbox::geojson::feature_collection>();
-        source->setGeoJSON(geojson);
+    if (self.URL) {
+        NSURL *url = self.URL.mgl_URLByStandardizingScheme;
+        source->setURL(url.absoluteString.UTF8String);
     } else {
-        source->setURL(self.data.UTF8String);
+        NSString *string = [[NSString alloc] initWithData:self.geoJSONData encoding:NSUTF8StringEncoding];
+        const auto geojson = mapbox::geojson::parse(string.UTF8String).get<mapbox::geojson::feature_collection>();
+        source->setGeoJSON(geojson);
+        _features = MGLFeaturesFromMBGLFeatures(geojson);
     }
     return std::move(source);
 }