Drain socket before throwing (#79289)

packages/flutter/lib/src/painting/_network_image_io.dart

@@ -96,6 +96,7 @@ class NetworkImage extends image_provider.ImageProvider<image_provider.NetworkIm
         // The network may be only temporarily unavailable, or the file will be
         // added on the server later. Avoid having future calls to resolve
         // fail to check the network again.
+        await response.drain<List<int>>();
         throw image_provider.NetworkImageLoadException(statusCode: response.statusCode, uri: resolved);
       }
 

packages/flutter/test/painting/image_provider_network_image_test.dart

@@ -35,7 +35,7 @@ void main() {
     PaintingBinding.instance!.imageCache!.clearLiveImages();
   });
 
-  test('Expect thrown exception with statusCode - evicts from cache', () async {
+  test('Expect thrown exception with statusCode - evicts from cache and drains', () async {
     final int errorStatusCode = HttpStatus.notFound;
     const String requestUrl = 'foo-url';
 
@@ -68,6 +68,7 @@ void main() {
         .having((NetworkImageLoadException e) => e.statusCode, 'statusCode', errorStatusCode)
         .having((NetworkImageLoadException e) => e.uri, 'uri', Uri.base.resolve(requestUrl)),
     );
+    expect(httpClient.request.response.drained, true);
   }, skip: isBrowser); // Browser implementation does not use HTTP client but an <img> tag.
 
   test('Uses the HttpClient provided by debugNetworkImageHttpClientProvider if set', () async {
@@ -234,6 +235,8 @@ class _FakeHttpClientRequest extends Fake implements HttpClientRequest {
 }
 
 class _FakeHttpClientResponse extends Fake implements HttpClientResponse {
+  bool drained = false;
+
   @override
   int statusCode = HttpStatus.ok;
 
@@ -254,6 +257,12 @@ class _FakeHttpClientResponse extends Fake implements HttpClientResponse {
       cancelOnError: cancelOnError,
     );
   }
+
+  @override
+  Future<E> drain<E>([E? futureValue]) async {
+    drained = true;
+    return futureValue ?? <int>[] as E;
+  }
 }
 
 class FakeCodec implements Codec {