[tests] Don't call the callback for cancelled responses

StubFileSource gets an optional Response return type. Returning null means "cancelled; don't call the callback".

Fixes #3784

test/fixtures/stub_file_source.cpp

@@ -22,7 +22,9 @@ StubFileSource::StubFileSource() {
         // Explicit move to avoid iterator invalidation if ~StubFileRequest gets called within the loop.
         auto pending_ = std::move(pending);
         for (auto& pair : pending_) {
-            pair.second.second(pair.second.first);
+            if (pair.second.first) {
+                pair.second.second(*pair.second.first);
+            }
         }
     });
 }
@@ -35,7 +37,7 @@ std::unique_ptr<FileRequest> StubFileSource::request(const Resource& resource, C
     return std::move(req);
 }
 
-Response StubFileSource::defaultResponse(const Resource& resource) {
+optional<Response> StubFileSource::defaultResponse(const Resource& resource) {
     switch (resource.kind) {
     case Resource::Kind::Style:
         if (!styleResponse) throw std::runtime_error("unexpected style request");

test/fixtures/stub_file_source.hpp

@@ -16,25 +16,25 @@ public:
     std::unique_ptr<FileRequest> request(const Resource&, Callback) override;
 
     // You can set the response callback on a global level by assigning this callback:
-    std::function<Response (const Resource&)> response = [this] (const Resource& resource) {
+    std::function<optional<Response> (const Resource&)> response = [this] (const Resource& resource) {
         return defaultResponse(resource);
     };
 
     // Or set per-kind responses by setting these callbacks:
-    std::function<Response (const Resource&)> styleResponse;
-    std::function<Response (const Resource&)> sourceResponse;
-    std::function<Response (const Resource&)> tileResponse;
-    std::function<Response (const Resource&)> glyphsResponse;
-    std::function<Response (const Resource&)> spriteJSONResponse;
-    std::function<Response (const Resource&)> spriteImageResponse;
+    std::function<optional<Response> (const Resource&)> styleResponse;
+    std::function<optional<Response> (const Resource&)> sourceResponse;
+    std::function<optional<Response> (const Resource&)> tileResponse;
+    std::function<optional<Response> (const Resource&)> glyphsResponse;
+    std::function<optional<Response> (const Resource&)> spriteJSONResponse;
+    std::function<optional<Response> (const Resource&)> spriteImageResponse;
 
 private:
     friend class StubFileRequest;
 
     // The default behavior is to throw if no per-kind callback has been set.
-    Response defaultResponse(const Resource&);
+    optional<Response> defaultResponse(const Resource&);
 
-    std::unordered_map<FileRequest*, std::pair<Response, Callback>> pending;
+    std::unordered_map<FileRequest*, std::pair<optional<Response>, Callback>> pending;
     util::Timer timer;
 };
 

test/sprite/sprite_store.cpp

@@ -299,7 +299,7 @@ TEST(SpriteStore, LoadingCancel) {
     test.fileSource.spriteImageResponse =
     test.fileSource.spriteJSONResponse = [&] (const Resource&) {
         test.end();
-        return Response();
+        return optional<Response>();
     };
 
     test.observer.spriteLoaded = [&] () {

test/style/glyph_store.cpp

@@ -134,7 +134,7 @@ TEST(GlyphStore, LoadingCancel) {
 
     test.fileSource.glyphsResponse = [&] (const Resource&) {
         test.end();
-        return Response();
+        return optional<Response>();
     };
 
     test.observer.glyphsLoaded = [&] (const std::string&, const GlyphRange&) {

test/style/source.cpp

@@ -240,7 +240,7 @@ TEST(Source, RasterTileCancel) {
 
     test.fileSource.tileResponse = [&] (const Resource&) {
         test.end();
-        return Response();
+        return optional<Response>();
     };
 
     test.observer.tileLoaded = [&] (Source&, const TileID&, bool) {
@@ -267,7 +267,7 @@ TEST(Source, VectorTileCancel) {
 
     test.fileSource.tileResponse = [&] (const Resource&) {
         test.end();
-        return Response();
+        return optional<Response>();
     };
 
     test.observer.tileLoaded = [&] (Source&, const TileID&, bool) {