[core] Use variant<std::string, Tileset> in TileSource

A tile source can either specify a URL to TileJSON, or inline TileJSON.

test/style/tile_source.cpp

@@ -0,0 +1,37 @@
+#include <mbgl/test/util.hpp>
+
+#include <mbgl/style/tile_source.hpp>
+#include <mbgl/util/io.hpp>
+
+using namespace mbgl;
+using namespace mbgl::style;
+
+TEST(TileSource, ParseTileJSONRaster) {
+    auto result = TileSource::parseTileJSON(
+        util::read_file("test/fixtures/style_parser/tilejson.raster.json"),
+        "mapbox://mapbox.satellite",
+        SourceType::Raster,
+        256);
+
+    EXPECT_EQ(0, result.zoomRange.min);
+    EXPECT_EQ(15, result.zoomRange.max);
+    EXPECT_EQ("attribution", result.attribution);
+#if !defined(__ANDROID__) && !defined(__APPLE__)
+    EXPECT_EQ("mapbox://tiles/mapbox.satellite/{z}/{x}/{y}{ratio}.webp", result.tiles[0]);
+#else
+    EXPECT_EQ("mapbox://tiles/mapbox.satellite/{z}/{x}/{y}{ratio}.png", result.tiles[0]);
+#endif
+}
+
+TEST(TileSource, ParseTileJSONVector) {
+    auto result = TileSource::parseTileJSON(
+        util::read_file("test/fixtures/style_parser/tilejson.vector.json"),
+        "mapbox://mapbox.streets",
+        SourceType::Vector,
+        256);
+
+    EXPECT_EQ(0, result.zoomRange.min);
+    EXPECT_EQ(15, result.zoomRange.max);
+    EXPECT_EQ("attribution", result.attribution);
+    EXPECT_EQ("mapbox://tiles/mapbox.streets/{z}/{x}/{y}.vector.pbf", result.tiles[0]);
+}