Fix Image.network not using cache when headers are specified (#176831)

Fix a bug introduced by 97aae2ad3 (#171916), where `hashCode` is giving
different results for values which `==` says are equal. Which broke
caching for uses of `Image.network` widget when `headers` map was
passed.

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

@@ -6,6 +6,7 @@ import 'dart:async';
 import 'dart:io';
 import 'dart:ui' as ui;
 
+import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 
 import 'binding.dart';
@@ -171,7 +172,7 @@ class NetworkImage extends image_provider.ImageProvider<image_provider.NetworkIm
   }
 
   @override
-  int get hashCode => Object.hash(url, scale, headers);
+  int get hashCode => Object.hash(url, scale, const MapEquality<String, String>().hash(headers));
 
   @override
   String toString() =>

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

@@ -6,6 +6,7 @@ import 'dart:async';
 import 'dart:js_interop';
 import 'dart:ui' as ui;
 
+import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 
 import '../web.dart' as web;
@@ -250,7 +251,12 @@ class NetworkImage extends image_provider.ImageProvider<image_provider.NetworkIm
   }
 
   @override
-  int get hashCode => Object.hash(url, scale, webHtmlElementStrategy, headers);
+  int get hashCode => Object.hash(
+    url,
+    scale,
+    webHtmlElementStrategy,
+    const MapEquality<String, String>().hash(headers),
+  );
 
   @override
   String toString() =>

packages/flutter/test/painting/image_provider_network_image_test.dart

@@ -288,6 +288,51 @@ void main() {
     debugNetworkImageHttpClientProvider = null;
   }, skip: isBrowser); // [intended] Browser does not resolve images this way.
 
+  test('Network image with same arguments uses cache', () async {
+    final _FakeHttpClient mockHttpClient = _FakeHttpClient();
+    debugNetworkImageHttpClientProvider = () => mockHttpClient;
+    mockHttpClient.request.response
+      ..statusCode = HttpStatus.ok
+      ..contentLength = kTransparentImage.length
+      ..content = <Uint8List>[Uint8List.fromList(kTransparentImage)];
+
+    final Completer<void> imageAvailable1 = Completer<void>();
+    final ImageProvider imageProvider1 = NetworkImage(
+      nonconst('testing.url'),
+      headers: nonconst(<String, String>{'key': 'value'}),
+    );
+    expect(imageCache.liveImageCount, 0);
+
+    final ImageStream result1 = imageProvider1.resolve(ImageConfiguration.empty);
+    result1.addListener(
+      ImageStreamListener((ImageInfo image, bool synchronousCall) {
+        imageAvailable1.complete();
+      }),
+    );
+    await imageAvailable1.future;
+    expect(imageCache.liveImageCount, 1);
+
+    // NetworkImage should not make another request.
+    mockHttpClient.request.response.statusCode = HttpStatus.badRequest;
+
+    final Completer<void> imageAvailable2 = Completer<void>();
+    final ImageProvider imageProvider2 = NetworkImage(
+      nonconst('testing.url'),
+      headers: nonconst(<String, String>{'key': 'value'}),
+    );
+
+    final ImageStream result2 = imageProvider2.resolve(ImageConfiguration.empty);
+    result2.addListener(
+      ImageStreamListener((ImageInfo image, bool synchronousCall) {
+        imageAvailable2.complete();
+      }),
+    );
+    await imageAvailable2.future;
+    expect(imageCache.liveImageCount, 1);
+
+    debugNetworkImageHttpClientProvider = null;
+  }, skip: isBrowser); // [intended] Browser does not resolve images this way.
+
   test('Network image sets tag', () async {
     const String url = 'http://test.png';
     const int chunkSize = 8;
@@ -340,6 +385,9 @@ class _FakeHttpClient extends Fake implements HttpClient {
 class _FakeHttpClientRequest extends Fake implements HttpClientRequest {
   final _FakeHttpClientResponse response = _FakeHttpClientResponse();
 
+  @override
+  final HttpHeaders headers = _FakeHttpHeaders();
+
   @override
   Future<HttpClientResponse> close() async {
     return response;
@@ -379,3 +427,8 @@ class _FakeHttpClientResponse extends Fake implements HttpClientResponse {
     return futureValue ?? futureValue as E; // Mirrors the implementation in Stream.
   }
 }
+
+class _FakeHttpHeaders extends Fake implements HttpHeaders {
+  @override
+  void add(String name, Object value, {bool preserveHeaderCase = false}) {}
+}