Cancel pending style request when loading style JSON (#3709)

Co-authored-by: Tim Sylvester <tim@wetdogweather.com>

test/style/style.test.cpp

@@ -9,6 +9,7 @@
 #include <mbgl/style/layers/line_layer.hpp>
 #include <mbgl/util/io.hpp>
 #include <mbgl/util/run_loop.hpp>
+#include <mbgl/test/delayed_file_source.hpp>
 
 #include <memory>
 
@@ -110,6 +111,38 @@ TEST(Style, RemoveSourceInUse) {
     EXPECT_EQ(log.count(logMessage), 1u);
 }
 
+TEST(Style, LoadJSONCancelsPendingLoadURL) {
+    util::RunLoop loop;
+
+    auto fileSource = std::make_shared<::DelayedFileSource>();
+    Style::Impl style{fileSource, 1.0, {Scheduler::GetBackground(), {}}};
+
+    // Start loading a URL (this will be pending)
+    auto url = "http://some-url";
+    style.loadURL(url);
+
+    // Before the URL request completes, load JSON directly
+    const std::string json = R"STYLE({
+        "version": 8,
+        "name": "Test Style",
+        "sources": {},
+        "layers": []
+    })STYLE";
+    style.loadJSON(json);
+
+    // The style should now be loaded with our JSON content
+    ASSERT_EQ("Test Style", style.getName());
+    ASSERT_EQ("", style.getURL());
+    ASSERT_TRUE(style.getJSON().find("Test Style") != std::string::npos);
+
+    // Now respond to the original URL request - this should be ignored
+    fileSource->respondToRequest(R"STYLE({"version":8,"name":"Streets"})STYLE");
+
+    // The style should still show our JSON content, not the URL content
+    ASSERT_EQ("Test Style", style.getName());
+    ASSERT_NE("Streets", style.getName());
+}
+
 TEST(Style, SourceImplsOrder) {
     util::RunLoop loop;
     auto fileSource = std::make_shared<StubFileSource>();