Fuchsia step 1: add SDK version file and artifact download (#31073)

bin/internal/fuchsia.version

@@ -0,0 +1 @@
+Ow5Xdviq7OwKr7XNuf-Bw0nBMeAr849mFn7gc_RUpzUC

packages/flutter_tools/lib/src/cache.dart

@@ -16,27 +16,53 @@ import 'base/platform.dart';
 import 'globals.dart';
 
 /// A tag for a set of development artifacts that need to be cached.
-enum DevelopmentArtifact {
+class DevelopmentArtifact {
+
+  const DevelopmentArtifact._(this.name, {this.unstable = false});
+
+  /// The name of the artifact.
+  ///
+  /// This should match the flag name in precache.dart
+  final String name;
+
+  /// Whether this artifact should not be usable on stable branches.
+  final bool unstable;
+
   /// Artifacts required for Android development.
-  android,
+  static const DevelopmentArtifact android = DevelopmentArtifact._('android');
 
   /// Artifacts required for iOS development.
-  iOS,
+  static const DevelopmentArtifact iOS = DevelopmentArtifact._('ios');
 
   /// Artifacts required for web development,
-  web,
+  static const DevelopmentArtifact web = DevelopmentArtifact._('web', unstable: true);
 
   /// Artifacts required for desktop macOS.
-  macOS,
+  static const DevelopmentArtifact macOS = DevelopmentArtifact._('macos', unstable: true);
 
   /// Artifacts required for desktop Windows.
-  windows,
+  static const DevelopmentArtifact windows = DevelopmentArtifact._('windows', unstable: true);
 
   /// Artifacts required for desktop linux.
-  linux,
+  static const DevelopmentArtifact linux = DevelopmentArtifact._('linux', unstable: true);
+
+  /// Artifacts required for Fuchsia.
+  static const DevelopmentArtifact fuchsia = DevelopmentArtifact._('fuchsia', unstable: true);
 
   /// Artifacts required by all developments.
-  universal,
+  static const DevelopmentArtifact universal = DevelopmentArtifact._('universal');
+
+  /// The vaulues of DevelopmentArtifacts.
+  static final List<DevelopmentArtifact> values = <DevelopmentArtifact>[
+    android,
+    iOS,
+    web,
+    macOS,
+    windows,
+    linux,
+    fuchsia,
+    universal,
+  ];
 }
 
 /// A wrapper around the `bin/cache/` directory.
@@ -54,6 +80,7 @@ class Cache {
       _artifacts.add(WindowsEngineArtifacts(this));
       _artifacts.add(MacOSEngineArtifacts(this));
       _artifacts.add(LinuxEngineArtifacts(this));
+      _artifacts.add(FuchsiaCacheArtifacts(this));
     } else {
       _artifacts.addAll(artifacts);
     }
@@ -155,12 +182,19 @@ class Cache {
     return _dartSdkVersion;
   }
 
-  String _engineRevision;
-
+  /// The current version of the Flutter engine the flutter tool will download.
   String get engineRevision {
     _engineRevision ??= getVersionFor('engine');
     return _engineRevision;
   }
+  String _engineRevision;
+
+  /// The current version of the Fuchsia SDK the flutter tool will download.
+  String get fuchsiaRevision {
+    _fuchsiaRevision ??= getVersionFor('fuchsia');
+    return _fuchsiaRevision;
+  }
+  String _fuchsiaRevision;
 
   static Cache get instance => context[Cache];
 
@@ -817,6 +851,33 @@ class GradleWrapper extends CachedArtifact {
   }
 }
 
+/// The Fuchsia core SDK.
+class FuchsiaCacheArtifacts extends CachedArtifact {
+  FuchsiaCacheArtifacts(Cache cache) : super('fuchsia', cache, const <DevelopmentArtifact> {
+    DevelopmentArtifact.fuchsia,
+  });
+
+  static const String _cipdBaseUrl = 'https://chrome-infra-packages.appspot.com/dl';
+  static const String _macOSSdk = 'fuchsia/sdk/core/mac-amd64';
+  static const String _linuxSdk = 'fuchsia/sdk/core/linux-amd64';
+
+ @override
+  Future<void> updateInner() async {
+    // Step 1: Determine variant of Fuchsia SDK to download.
+    String packageName;
+    if (platform.isLinux) {
+      packageName = _linuxSdk;
+    } else if (platform.isMacOS) {
+      packageName = _macOSSdk;
+    } else {
+      // Unsupported.
+      return;
+    }
+    final String url = '$_cipdBaseUrl/$packageName/+/$version';
+    await _downloadZipArchive('Downloading package fuchsia SDK...', Uri.parse(url), location);
+  }
+}
+
 // Many characters are problematic in filenames, especially on Windows.
 final Map<int, List<int>> _flattenNameSubstitutions = <int, List<int>>{
   r'@'.codeUnitAt(0): '@@'.codeUnits,

packages/flutter_tools/lib/src/commands/precache.dart

@@ -25,6 +25,10 @@ class PrecacheCommand extends FlutterCommand {
         help: 'Precache artifacts for windows desktop development');
     argParser.addFlag('macos', negatable: true, defaultsTo: false,
         help: 'Precache artifacts for macOS desktop development');
+    argParser.addFlag('fuchsia', negatable: true, defaultsTo: false,
+        help: 'Precache artifacts for Fuchsia development');
+    argParser.addFlag('universal', negatable: true, defaultsTo: true,
+        help: 'Precache artifacts required for all developments');
   }
 
   @override
@@ -41,28 +45,16 @@ class PrecacheCommand extends FlutterCommand {
     if (argResults['all-platforms']) {
       cache.includeAllPlatforms = true;
     }
-    final Set<DevelopmentArtifact> requiredArtifacts = <DevelopmentArtifact>{ DevelopmentArtifact.universal };
-    if (argResults['android']) {
-      requiredArtifacts.add(DevelopmentArtifact.android);
-    }
-    if (argResults['ios']) {
-      requiredArtifacts.add(DevelopmentArtifact.iOS);
-    }
-    if (!FlutterVersion.instance.isStable) {
-      if (argResults['web']) {
-        requiredArtifacts.add(DevelopmentArtifact.web);
+    final Set<DevelopmentArtifact> requiredArtifacts = <DevelopmentArtifact>{};
+    for (DevelopmentArtifact artifact in DevelopmentArtifact.values) {
+      // Don't include unstable artifacts on stable branches.
+      if (FlutterVersion.instance.isStable && artifact.unstable) {
+        continue;
       }
-      if (argResults['linux']) {
-        requiredArtifacts.add(DevelopmentArtifact.linux);
-      }
-      if (argResults['windows']) {
-        requiredArtifacts.add(DevelopmentArtifact.windows);
-      }
-      if (argResults['macos']) {
-        requiredArtifacts.add(DevelopmentArtifact.macOS);
+      if (argResults[artifact.name]) {
+        requiredArtifacts.add(artifact);
       }
     }
-
     if (cache.isUpToDate()) {
       printStatus('Already up-to-date.');
     } else {

packages/flutter_tools/test/commands/precache_test.dart

@@ -27,7 +27,7 @@ void main() {
       final PrecacheCommand command = PrecacheCommand();
       applyMocksToCommand(command);
       await createTestCommandRunner(command).run(
-        const <String>['precache', '--ios', '--android', '--web', '--macos', '--linux', '--windows']
+        const <String>['precache', '--ios', '--android', '--web', '--macos', '--linux', '--windows', '--fuchsia']
       );
       expect(artifacts, unorderedEquals(<DevelopmentArtifact>{
         DevelopmentArtifact.universal,
@@ -37,6 +37,7 @@ void main() {
         DevelopmentArtifact.macOS,
         DevelopmentArtifact.linux,
         DevelopmentArtifact.windows,
+        DevelopmentArtifact.fuchsia,
       }));
     }, overrides: <Type, Generator>{
       Cache: () => cache,
@@ -51,7 +52,7 @@ void main() {
       final PrecacheCommand command = PrecacheCommand();
       applyMocksToCommand(command);
       await createTestCommandRunner(command).run(
-       const <String>['precache', '--ios', '--android', '--web', '--macos', '--linux', '--windows']
+       const <String>['precache', '--ios', '--android', '--web', '--macos', '--linux', '--windows', '--fuchsia']
       );
      expect(artifacts, unorderedEquals(<DevelopmentArtifact>{
        DevelopmentArtifact.universal,