Automatically URI encode asset keys (#35270)

lib/ui/BUILD.gn

@@ -185,6 +185,7 @@ if (enable_unittests) {
     dart_main = "fixtures/ui_test.dart"
     fixtures = [
       "fixtures/DashInNooglerHat.jpg",
+      "fixtures/DashInNooglerHat%20WithSpace.jpg",
       "fixtures/Horizontal.jpg",
       "fixtures/Horizontal.png",
       "fixtures/hello_loop_2.gif",

lib/ui/painting.dart

@@ -5674,9 +5674,14 @@ class ImmutableBuffer extends NativeFieldWrapperClass1 {
   ///
   /// Throws an [Exception] if the asset does not exist.
   static Future<ImmutableBuffer> fromAsset(String assetKey) {
+    // The flutter tool converts all asset keys with spaces into URI
+    // encoded paths (replacing ' ' with '%20', for example). We perform
+    // the same encoding here so that users can load assets with the same
+    // key they have written in the pubspec.
+    final String encodedKey = Uri(path: Uri.encodeFull(assetKey)).path;
     final ImmutableBuffer instance = ImmutableBuffer._(0);
     return _futurize((_Callback<int> callback) {
-      return instance._initFromAsset(assetKey, callback);
+      return instance._initFromAsset(encodedKey, callback);
     }).then((int length) => instance.._length = length);
   }
 

testing/dart/assets_test.dart

@@ -27,6 +27,13 @@ void main() {
     expect(buffer.length == 354679, true);
   });
 
+  test('Can load an asset with a space in the key', () async {
+    // This assets actual path is "fixtures/DashInNooglerHat%20WithSpace.jpg"
+    final ImmutableBuffer buffer = await ImmutableBuffer.fromAsset('DashInNooglerHat WithSpace.jpg');
+
+    expect(buffer.length == 354679, true);
+  });
+
   test('can dispose immutable buffer', () async {
     final ImmutableBuffer buffer = await ImmutableBuffer.fromAsset('DashInNooglerHat.jpg');