Lazy cache 4 (#29785)

packages/flutter_tools/lib/src/base/build.dart

@@ -85,7 +85,6 @@ class AOTSnapshotter {
     if (fs.file('pubspec.yaml').existsSync()) {
       flutterProject = await FlutterProject.current();
     }
-    final FlutterEngine engine = FlutterEngine(cache);
     if (!_isValidAotPlatform(platform, buildMode)) {
       printError('${getNameForTargetPlatform(platform)} does not support AOT compilation.');
       return 1;
@@ -187,7 +186,7 @@ class AOTSnapshotter {
         'entryPoint': mainPath,
         'sharedLib': buildSharedLibrary.toString(),
         'extraGenSnapshotOptions': extraGenSnapshotOptions.join(' '),
-        'engineHash': engine.version,
+        'engineHash': Cache.instance.engineRevision,
         'buildersUsed': '${flutterProject != null ? flutterProject.hasBuilders : false}',
       },
       depfilePaths: <String>[],

packages/flutter_tools/lib/src/cache.dart

@@ -15,6 +15,30 @@ import 'base/os.dart';
 import 'base/platform.dart';
 import 'globals.dart';
 
+/// A tag for a set of development artifacts that need to be cached.
+enum DevelopmentArtifact {
+  /// Artifacts required for Android development.
+  android,
+
+  /// Artifacts required for iOS development.
+  iOS,
+
+  /// Artifacts required for web development,
+  web,
+
+  /// Artifacts required for desktop macOS.
+  macOS,
+
+  /// Artifacts required for desktop Windows.
+  windows,
+
+  /// Artifacts required for desktop linux.
+  linux,
+
+  /// Artifacts required by all developments.
+  universal,
+}
+
 /// A wrapper around the `bin/cache/` directory.
 class Cache {
   /// [rootOverride] is configurable for testing.
@@ -22,9 +46,11 @@ class Cache {
   Cache({ Directory rootOverride, List<CachedArtifact> artifacts }) : _rootOverride = rootOverride {
     if (artifacts == null) {
       _artifacts.add(MaterialFonts(this));
-      _artifacts.add(FlutterEngine(this));
+      _artifacts.add(AndroidEngineArtifacts(this));
+      _artifacts.add(IOSEngineArtifacts(this));
       _artifacts.add(GradleWrapper(this));
       _artifacts.add(FlutterWebSdk(this));
+      _artifacts.add(FlutterSdk(this));
     } else {
       _artifacts.addAll(artifacts);
     }
@@ -194,7 +220,7 @@ class Cache {
     return isOlderThanReference(entity: entity, referenceFile: flutterToolsStamp);
   }
 
-  bool isUpToDate() => _artifacts.every((CachedArtifact artifact) => artifact.isUpToDate());
+  bool isUpToDate(Set<DevelopmentArtifact> requiredArtifacts) => _artifacts.every((CachedArtifact artifact) => artifact.isUpToDate(requiredArtifacts));
 
   Future<String> getThirdPartyFile(String urlStr, String serviceName) async {
     final Uri url = Uri.parse(urlStr);
@@ -217,13 +243,16 @@ class Cache {
     return cachedFile.path;
   }
 
-  Future<void> updateAll() async {
-    if (!_lockEnabled)
+  /// Update the cache to contain all `requiredArtifacts`.
+  Future<void> updateAll(Set<DevelopmentArtifact> requiredArtifacts) async {
+    if (!_lockEnabled) {
       return;
+    }
     try {
       for (CachedArtifact artifact in _artifacts) {
-        if (!artifact.isUpToDate())
+        if (!artifact.isUpToDate(requiredArtifacts)) {
           await artifact.update();
+        }
       }
     } on SocketException catch (e) {
       if (_hostsBlockedInChina.contains(e.address?.host)) {
@@ -237,15 +266,34 @@ class Cache {
       rethrow;
     }
   }
+
+  Future<bool> areRemoteArtifactsAvailable({
+    String engineVersion,
+    bool includeAllPlatforms = true,
+  }) async {
+    final bool includeAllPlatformsState = cache.includeAllPlatforms;
+    bool allAvailible = true;
+    cache.includeAllPlatforms = includeAllPlatforms;
+    for (CachedArtifact cachedArtifact in _artifacts) {
+      if (cachedArtifact is EngineCachedArtifact) {
+        allAvailible &= await cachedArtifact.checkForArtifacts(engineVersion);
+      }
+    }
+    cache.includeAllPlatforms = includeAllPlatformsState;
+    return allAvailible;
+  }
 }
 
 /// An artifact managed by the cache.
 abstract class CachedArtifact {
-  CachedArtifact(this.name, this.cache);
+  CachedArtifact(this.name, this.cache, this.developmentArtifacts);
 
   final String name;
   final Cache cache;
 
+  /// All development artifacts this cache provides.
+  final Set<DevelopmentArtifact> developmentArtifacts;
+
   Directory get location => cache.getArtifactDirectory(name);
   String get version => cache.getVersionFor(name);
 
@@ -255,18 +303,25 @@ abstract class CachedArtifact {
   /// starting from scratch.
   final List<File> _downloadedFiles = <File>[];
 
-  bool isUpToDate() {
-    if (!location.existsSync())
+  bool isUpToDate(Set<DevelopmentArtifact> requiredArtifacts) {
+    // If the set of required artifacts does not include any from this cache,
+    // then we can claim we are up to date to skip downloading.
+    if (!requiredArtifacts.any(developmentArtifacts.contains)) {
+      return true;
+    }
+    if (!location.existsSync()) {
       return false;
-    if (version != cache.getStampFor(name))
+    }
+    if (version != cache.getStampFor(name)) {
       return false;
+    }
     return isUpToDateInner();
   }
 
   Future<void> update() async {
-    if (location.existsSync())
-      location.deleteSync(recursive: true);
-    location.createSync(recursive: true);
+    if (!location.existsSync()) {
+      location.createSync(recursive: true);
+    }
     await updateInner();
     cache.setStampFor(name, version);
     _removeDownloadedFiles();
@@ -355,7 +410,11 @@ void _maybeWarnAboutStorageOverride(String overrideUrl) {
 
 /// A cached artifact containing fonts used for Material Design.
 class MaterialFonts extends CachedArtifact {
-  MaterialFonts(Cache cache) : super('material_fonts', cache);
+  MaterialFonts(Cache cache) : super(
+    'material_fonts',
+    cache,
+    const <DevelopmentArtifact>{ DevelopmentArtifact.universal },
+  );
 
   @override
   Future<void> updateInner() {
@@ -369,7 +428,11 @@ class MaterialFonts extends CachedArtifact {
 ///
 /// This SDK references code within the regular Dart sdk to reduce download size.
 class FlutterWebSdk extends CachedArtifact {
-  FlutterWebSdk(Cache cache) : super('flutter_web_sdk', cache);
+  FlutterWebSdk(Cache cache) : super(
+    'flutter_web_sdk',
+    cache,
+    const <DevelopmentArtifact>{ DevelopmentArtifact.web },
+  );
 
   @override
   Directory get location => cache.getWebSdkDirectory();
@@ -405,130 +468,37 @@ class FlutterWebSdk extends CachedArtifact {
   }
 }
 
-/// A cached artifact containing the Flutter engine binaries.
-class FlutterEngine extends CachedArtifact {
-  FlutterEngine(Cache cache) : super('engine', cache);
-
-  List<String> _getPackageDirs() => const <String>['sky_engine'];
-
-  // Return a list of (cache directory path, download URL path) tuples.
-  List<List<String>> _getBinaryDirs() {
-    final List<List<String>> binaryDirs = <List<String>>[];
-
-    binaryDirs.add(<String>['common', 'flutter_patched_sdk.zip']);
-
-    if (cache.includeAllPlatforms)
-      binaryDirs
-        ..addAll(_osxBinaryDirs)
-        ..addAll(_linuxBinaryDirs)
-        ..addAll(_windowsBinaryDirs)
-        ..addAll(_androidBinaryDirs)
-        ..addAll(_iosBinaryDirs)
-        ..addAll(_dartSdks);
-    else if (platform.isLinux)
-      binaryDirs
-        ..addAll(_linuxBinaryDirs)
-        ..addAll(_androidBinaryDirs);
-    else if (platform.isMacOS)
-      binaryDirs
-        ..addAll(_osxBinaryDirs)
-        ..addAll(_androidBinaryDirs)
-        ..addAll(_iosBinaryDirs);
-    else if (platform.isWindows)
-      binaryDirs
-        ..addAll(_windowsBinaryDirs)
-        ..addAll(_androidBinaryDirs);
-
-    return binaryDirs;
-  }
-
-  List<List<String>> get _osxBinaryDirs => <List<String>>[
-    <String>['darwin-x64', 'darwin-x64/artifacts.zip'],
-    <String>['android-arm-profile/darwin-x64', 'android-arm-profile/darwin-x64.zip'],
-    <String>['android-arm-release/darwin-x64', 'android-arm-release/darwin-x64.zip'],
-    <String>['android-arm64-profile/darwin-x64', 'android-arm64-profile/darwin-x64.zip'],
-    <String>['android-arm64-release/darwin-x64', 'android-arm64-release/darwin-x64.zip'],
-    <String>['android-arm-dynamic-profile/darwin-x64', 'android-arm-dynamic-profile/darwin-x64.zip'],
-    <String>['android-arm-dynamic-release/darwin-x64', 'android-arm-dynamic-release/darwin-x64.zip'],
-    <String>['android-arm64-dynamic-profile/darwin-x64', 'android-arm64-dynamic-profile/darwin-x64.zip'],
-    <String>['android-arm64-dynamic-release/darwin-x64', 'android-arm64-dynamic-release/darwin-x64.zip'],
-  ];
+abstract class EngineCachedArtifact extends CachedArtifact {
+  EngineCachedArtifact(
+    Cache cache,
+    Set<DevelopmentArtifact> requiredArtifacts,
+  ) : super('engine', cache, requiredArtifacts);
 
-  List<List<String>> get _linuxBinaryDirs => <List<String>>[
-    <String>['linux-x64', 'linux-x64/artifacts.zip'],
-    <String>['android-arm-profile/linux-x64', 'android-arm-profile/linux-x64.zip'],
-    <String>['android-arm-release/linux-x64', 'android-arm-release/linux-x64.zip'],
-    <String>['android-arm64-profile/linux-x64', 'android-arm64-profile/linux-x64.zip'],
-    <String>['android-arm64-release/linux-x64', 'android-arm64-release/linux-x64.zip'],
-    <String>['android-arm-dynamic-profile/linux-x64', 'android-arm-dynamic-profile/linux-x64.zip'],
-    <String>['android-arm-dynamic-release/linux-x64', 'android-arm-dynamic-release/linux-x64.zip'],
-    <String>['android-arm64-dynamic-profile/linux-x64', 'android-arm64-dynamic-profile/linux-x64.zip'],
-    <String>['android-arm64-dynamic-release/linux-x64', 'android-arm64-dynamic-release/linux-x64.zip'],
-  ];
+  /// Return a list of (directory path, download URL path) tuples.
+  List<List<String>> getBinaryDirs();
 
-  List<List<String>> get _windowsBinaryDirs => <List<String>>[
-    <String>['windows-x64', 'windows-x64/artifacts.zip'],
-    <String>['android-arm-profile/windows-x64', 'android-arm-profile/windows-x64.zip'],
-    <String>['android-arm-release/windows-x64', 'android-arm-release/windows-x64.zip'],
-    <String>['android-arm64-profile/windows-x64', 'android-arm64-profile/windows-x64.zip'],
-    <String>['android-arm64-release/windows-x64', 'android-arm64-release/windows-x64.zip'],
-    <String>['android-arm-dynamic-profile/windows-x64', 'android-arm-dynamic-profile/windows-x64.zip'],
-    <String>['android-arm-dynamic-release/windows-x64', 'android-arm-dynamic-release/windows-x64.zip'],
-    <String>['android-arm64-dynamic-profile/windows-x64', 'android-arm64-dynamic-profile/windows-x64.zip'],
-    <String>['android-arm64-dynamic-release/windows-x64', 'android-arm64-dynamic-release/windows-x64.zip'],
-  ];
+  /// A list of cache directory paths to which the LICENSE file should be copied.
+  List<String> getLicenseDirs();
 
-  List<List<String>> get _androidBinaryDirs => <List<String>>[
-    <String>['android-x86', 'android-x86/artifacts.zip'],
-    <String>['android-x64', 'android-x64/artifacts.zip'],
-    <String>['android-arm', 'android-arm/artifacts.zip'],
-    <String>['android-arm-profile', 'android-arm-profile/artifacts.zip'],
-    <String>['android-arm-release', 'android-arm-release/artifacts.zip'],
-    <String>['android-arm64', 'android-arm64/artifacts.zip'],
-    <String>['android-arm64-profile', 'android-arm64-profile/artifacts.zip'],
-    <String>['android-arm64-release', 'android-arm64-release/artifacts.zip'],
-    <String>['android-arm-dynamic-profile', 'android-arm-dynamic-profile/artifacts.zip'],
-    <String>['android-arm-dynamic-release', 'android-arm-dynamic-release/artifacts.zip'],
-    <String>['android-arm64-dynamic-profile', 'android-arm64-dynamic-profile/artifacts.zip'],
-    <String>['android-arm64-dynamic-release', 'android-arm64-dynamic-release/artifacts.zip'],
-  ];
-
-  List<List<String>> get _iosBinaryDirs => <List<String>>[
-    <String>['ios', 'ios/artifacts.zip'],
-    <String>['ios-profile', 'ios-profile/artifacts.zip'],
-    <String>['ios-release', 'ios-release/artifacts.zip'],
-  ];
-
-  List<List<String>> get _dartSdks => <List<String>> [
-    <String>['darwin-x64', 'dart-sdk-darwin-x64.zip'],
-    <String>['linux-x64', 'dart-sdk-linux-x64.zip'],
-    <String>['windows-x64', 'dart-sdk-windows-x64.zip'],
-  ];
-
-  // A list of cache directory paths to which the LICENSE file should be copied.
-  List<String> _getLicenseDirs() {
-    if (cache.includeAllPlatforms || platform.isMacOS) {
-      return const <String>['ios', 'ios-profile', 'ios-release'];
-    }
-    return const <String>[];
-  }
+  /// A list of the dart package directories to download.
+  List<String> getPackageDirs();
 
   @override
   bool isUpToDateInner() {
     final Directory pkgDir = cache.getCacheDir('pkg');
-    for (String pkgName in _getPackageDirs()) {
+    for (String pkgName in getPackageDirs()) {
       final String pkgPath = fs.path.join(pkgDir.path, pkgName);
       if (!fs.directory(pkgPath).existsSync())
         return false;
     }
 
-    for (List<String> toolsDir in _getBinaryDirs()) {
+    for (List<String> toolsDir in getBinaryDirs()) {
       final Directory dir = fs.directory(fs.path.join(location.path, toolsDir[0]));
       if (!dir.existsSync())
         return false;
     }
 
-    for (String licenseDir in _getLicenseDirs()) {
+    for (String licenseDir in getLicenseDirs()) {
       final File file = fs.file(fs.path.join(location.path, licenseDir, 'LICENSE'));
       if (!file.existsSync())
         return false;
@@ -541,15 +511,16 @@ class FlutterEngine extends CachedArtifact {
     final String url = '$_storageBaseUrl/flutter_infra/flutter/$version/';
 
     final Directory pkgDir = cache.getCacheDir('pkg');
-    for (String pkgName in _getPackageDirs()) {
+    for (String pkgName in getPackageDirs()) {
       final String pkgPath = fs.path.join(pkgDir.path, pkgName);
       final Directory dir = fs.directory(pkgPath);
-      if (dir.existsSync())
+      if (dir.existsSync()) {
         dir.deleteSync(recursive: true);
+      }
       await _downloadZipArchive('Downloading package $pkgName...', Uri.parse(url + pkgName + '.zip'), pkgDir);
     }
 
-    for (List<String> toolsDir in _getBinaryDirs()) {
+    for (List<String> toolsDir in getBinaryDirs()) {
       final String cacheDir = toolsDir[0];
       final String urlPath = toolsDir[1];
       final Directory dir = fs.directory(fs.path.join(location.path, cacheDir));
@@ -566,48 +537,35 @@ class FlutterEngine extends CachedArtifact {
     }
 
     final File licenseSource = fs.file(fs.path.join(Cache.flutterRoot, 'LICENSE'));
-    for (String licenseDir in _getLicenseDirs()) {
+    for (String licenseDir in getLicenseDirs()) {
       final String licenseDestinationPath = fs.path.join(location.path, licenseDir, 'LICENSE');
       await licenseSource.copy(licenseDestinationPath);
     }
   }
 
-  Future<bool> areRemoteArtifactsAvailable({
-    String engineVersion,
-    bool includeAllPlatforms = true,
-  }) async {
-    final bool includeAllPlatformsState = cache.includeAllPlatforms;
-    cache.includeAllPlatforms = includeAllPlatforms;
-
-    Future<bool> checkForArtifacts(String engineVersion) async {
-      engineVersion ??= version;
-      final String url = '$_storageBaseUrl/flutter_infra/flutter/$engineVersion/';
+  Future<bool> checkForArtifacts(String engineVersion) async {
+    engineVersion ??= version;
+    final String url = '$_storageBaseUrl/flutter_infra/flutter/$engineVersion/';
 
-      bool exists = false;
-      for (String pkgName in _getPackageDirs()) {
-        exists = await _doesRemoteExist('Checking package $pkgName is available...',
-            Uri.parse(url + pkgName + '.zip'));
-        if (!exists) {
-          return false;
-        }
+    bool exists = false;
+    for (String pkgName in getPackageDirs()) {
+      exists = await _doesRemoteExist('Checking package $pkgName is available...',
+          Uri.parse(url + pkgName + '.zip'));
+      if (!exists) {
+        return false;
       }
+    }
 
-      for (List<String> toolsDir in _getBinaryDirs()) {
-        final String cacheDir = toolsDir[0];
-        final String urlPath = toolsDir[1];
-        exists = await _doesRemoteExist('Checking $cacheDir tools are available...',
-            Uri.parse(url + urlPath));
-        if (!exists) {
-          return false;
-        }
+    for (List<String> toolsDir in getBinaryDirs()) {
+      final String cacheDir = toolsDir[0];
+      final String urlPath = toolsDir[1];
+      exists = await _doesRemoteExist('Checking $cacheDir tools are available...',
+          Uri.parse(url + urlPath));
+      if (!exists) {
+        return false;
       }
-
-      return true;
     }
-
-    final bool result = await checkForArtifacts(engineVersion);
-    cache.includeAllPlatforms = includeAllPlatformsState;
-    return result;
+    return true;
   }
 
 
@@ -622,9 +580,123 @@ class FlutterEngine extends CachedArtifact {
   }
 }
 
+
+/// A cached artifact containing the dart:ui source code.
+class FlutterSdk extends EngineCachedArtifact {
+  FlutterSdk(Cache cache) : super(
+    cache,
+    const <DevelopmentArtifact>{ DevelopmentArtifact.universal },
+  );
+
+  @override
+  List<String> getPackageDirs() => const <String>['sky_engine'];
+
+  @override
+  List<List<String>> getBinaryDirs() {
+    final List<List<String>> binaryDirs = <List<String>>[
+      <String>['common', 'flutter_patched_sdk.zip'],
+    ];
+    if (cache.includeAllPlatforms) {
+      binaryDirs.addAll(<List<String>>[
+        <String>['windows-x64', 'windows-x64/artifacts.zip'],
+        <String>['linux-x64', 'linux-x64/artifacts.zip'],
+        <String>['darwin-x64', 'darwin-x64/artifacts.zip'],
+      ]);
+    } else if (platform.isWindows) {
+      binaryDirs.addAll(<List<String>>[
+        <String>['windows-x64', 'windows-x64/artifacts.zip'],
+      ]);
+    } else if (platform.isMacOS) {
+      binaryDirs.addAll(<List<String>>[
+        <String>['darwin-x64', 'darwin-x64/artifacts.zip'],
+      ]);
+    } else if (platform.isLinux) {
+      binaryDirs.addAll(<List<String>>[
+        <String>['linux-x64', 'linux-x64/artifacts.zip'],
+      ]);
+    }
+    return binaryDirs;
+  }
+
+  @override
+  List<String> getLicenseDirs() => const <String>[];
+}
+
+class AndroidEngineArtifacts extends EngineCachedArtifact {
+  AndroidEngineArtifacts(Cache cache) : super(
+    cache,
+    const <DevelopmentArtifact>{ DevelopmentArtifact.android },
+  );
+
+  @override
+  List<String> getPackageDirs() => const <String>[];
+
+  @override
+  List<List<String>> getBinaryDirs() {
+    final List<List<String>> binaryDirs = <List<String>>[];
+    if (cache.includeAllPlatforms) {
+      binaryDirs
+        ..addAll(_osxBinaryDirs)
+        ..addAll(_linuxBinaryDirs)
+        ..addAll(_windowsBinaryDirs)
+        ..addAll(_androidBinaryDirs)
+        ..addAll(_dartSdks);
+    } else if (platform.isWindows) {
+      binaryDirs
+        ..addAll(_windowsBinaryDirs)
+        ..addAll(_androidBinaryDirs);
+    } else if (platform.isMacOS) {
+      binaryDirs
+        ..addAll(_osxBinaryDirs)
+        ..addAll(_androidBinaryDirs);
+    } else if (platform.isLinux) {
+      binaryDirs
+        ..addAll(_linuxBinaryDirs)
+        ..addAll(_androidBinaryDirs);
+    }
+    return binaryDirs;
+  }
+
+  @override
+  List<String> getLicenseDirs() { return <String>[]; }
+}
+
+class IOSEngineArtifacts extends EngineCachedArtifact {
+  IOSEngineArtifacts(Cache cache) : super(
+    cache,
+    <DevelopmentArtifact>{ DevelopmentArtifact.iOS },
+  );
+
+  @override
+  List<List<String>> getBinaryDirs() {
+    final List<List<String>> binaryDirs = <List<String>>[];
+    if (platform.isMacOS || cache.includeAllPlatforms) {
+      binaryDirs.addAll(_iosBinaryDirs);
+    }
+    return binaryDirs;
+  }
+
+  @override
+  List<String> getLicenseDirs() {
+    if (cache.includeAllPlatforms || platform.isMacOS) {
+      return const <String>['ios', 'ios-profile', 'ios-release'];
+    }
+    return const <String>[];
+  }
+
+  @override
+  List<String> getPackageDirs() {
+    return <String>[];
+  }
+}
+
 /// A cached artifact containing Gradle Wrapper scripts and binaries.
 class GradleWrapper extends CachedArtifact {
-  GradleWrapper(Cache cache) : super('gradle_wrapper', cache);
+  GradleWrapper(Cache cache) : super(
+    'gradle_wrapper',
+    cache,
+    const <DevelopmentArtifact>{ DevelopmentArtifact.android },
+  );
 
   List<String> get _gradleScripts => <String>['gradlew', 'gradlew.bat'];
 
@@ -644,8 +716,9 @@ class GradleWrapper extends CachedArtifact {
   @override
   bool isUpToDateInner() {
     final Directory wrapperDir = cache.getCacheDir(fs.path.join('artifacts', 'gradle_wrapper'));
-    if (!fs.directory(wrapperDir).existsSync())
+    if (!fs.directory(wrapperDir).existsSync()) {
       return false;
+    }
     for (String scriptName in _gradleScripts) {
       final File scriptFile = fs.file(fs.path.join(wrapperDir.path, scriptName));
       if (!scriptFile.existsSync())
@@ -706,6 +779,67 @@ Future<bool> _doesRemoteExist(String message, Uri url) async {
 
 /// Create the given [directory] and parents, as necessary.
 void _ensureExists(Directory directory) {
-  if (!directory.existsSync())
+  if (!directory.existsSync()) {
     directory.createSync(recursive: true);
+  }
 }
+
+const List<List<String>> _osxBinaryDirs = <List<String>>[
+  <String>['android-arm-profile/darwin-x64', 'android-arm-profile/darwin-x64.zip'],
+  <String>['android-arm-release/darwin-x64', 'android-arm-release/darwin-x64.zip'],
+  <String>['android-arm64-profile/darwin-x64', 'android-arm64-profile/darwin-x64.zip'],
+  <String>['android-arm64-release/darwin-x64', 'android-arm64-release/darwin-x64.zip'],
+  <String>['android-arm-dynamic-profile/darwin-x64', 'android-arm-dynamic-profile/darwin-x64.zip'],
+  <String>['android-arm-dynamic-release/darwin-x64', 'android-arm-dynamic-release/darwin-x64.zip'],
+  <String>['android-arm64-dynamic-profile/darwin-x64', 'android-arm64-dynamic-profile/darwin-x64.zip'],
+  <String>['android-arm64-dynamic-release/darwin-x64', 'android-arm64-dynamic-release/darwin-x64.zip'],
+];
+
+const List<List<String>> _linuxBinaryDirs = <List<String>>[
+  <String>['android-arm-profile/linux-x64', 'android-arm-profile/linux-x64.zip'],
+  <String>['android-arm-release/linux-x64', 'android-arm-release/linux-x64.zip'],
+  <String>['android-arm64-profile/linux-x64', 'android-arm64-profile/linux-x64.zip'],
+  <String>['android-arm64-release/linux-x64', 'android-arm64-release/linux-x64.zip'],
+  <String>['android-arm-dynamic-profile/linux-x64', 'android-arm-dynamic-profile/linux-x64.zip'],
+  <String>['android-arm-dynamic-release/linux-x64', 'android-arm-dynamic-release/linux-x64.zip'],
+  <String>['android-arm64-dynamic-profile/linux-x64', 'android-arm64-dynamic-profile/linux-x64.zip'],
+  <String>['android-arm64-dynamic-release/linux-x64', 'android-arm64-dynamic-release/linux-x64.zip'],
+];
+
+const List<List<String>> _windowsBinaryDirs = <List<String>>[
+  <String>['android-arm-profile/windows-x64', 'android-arm-profile/windows-x64.zip'],
+  <String>['android-arm-release/windows-x64', 'android-arm-release/windows-x64.zip'],
+  <String>['android-arm64-profile/windows-x64', 'android-arm64-profile/windows-x64.zip'],
+  <String>['android-arm64-release/windows-x64', 'android-arm64-release/windows-x64.zip'],
+  <String>['android-arm-dynamic-profile/windows-x64', 'android-arm-dynamic-profile/windows-x64.zip'],
+  <String>['android-arm-dynamic-release/windows-x64', 'android-arm-dynamic-release/windows-x64.zip'],
+  <String>['android-arm64-dynamic-profile/windows-x64', 'android-arm64-dynamic-profile/windows-x64.zip'],
+  <String>['android-arm64-dynamic-release/windows-x64', 'android-arm64-dynamic-release/windows-x64.zip'],
+];
+
+const List<List<String>> _androidBinaryDirs = <List<String>>[
+  <String>['android-x86', 'android-x86/artifacts.zip'],
+  <String>['android-x64', 'android-x64/artifacts.zip'],
+  <String>['android-arm', 'android-arm/artifacts.zip'],
+  <String>['android-arm-profile', 'android-arm-profile/artifacts.zip'],
+  <String>['android-arm-release', 'android-arm-release/artifacts.zip'],
+  <String>['android-arm64', 'android-arm64/artifacts.zip'],
+  <String>['android-arm64-profile', 'android-arm64-profile/artifacts.zip'],
+  <String>['android-arm64-release', 'android-arm64-release/artifacts.zip'],
+  <String>['android-arm-dynamic-profile', 'android-arm-dynamic-profile/artifacts.zip'],
+  <String>['android-arm-dynamic-release', 'android-arm-dynamic-release/artifacts.zip'],
+  <String>['android-arm64-dynamic-profile', 'android-arm64-dynamic-profile/artifacts.zip'],
+  <String>['android-arm64-dynamic-release', 'android-arm64-dynamic-release/artifacts.zip'],
+];
+
+const List<List<String>> _iosBinaryDirs = <List<String>>[
+  <String>['ios', 'ios/artifacts.zip'],
+  <String>['ios-profile', 'ios-profile/artifacts.zip'],
+  <String>['ios-release', 'ios-release/artifacts.zip'],
+];
+
+const List<List<String>> _dartSdks = <List<String>> [
+  <String>['darwin-x64', 'dart-sdk-darwin-x64.zip'],
+  <String>['linux-x64', 'dart-sdk-linux-x64.zip'],
+  <String>['windows-x64', 'dart-sdk-windows-x64.zip'],
+];

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

@@ -64,6 +64,11 @@ class AnalyzeCommand extends FlutterCommand {
   @override
   String get description => "Analyze the project's Dart code.";
 
+  @override
+  Set<DevelopmentArtifact> get requiredArtifacts => const <DevelopmentArtifact>{
+    DevelopmentArtifact.universal,
+  };
+
   @override
   bool get shouldRunPub {
     // If they're not analyzing the current project.

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

@@ -8,7 +8,7 @@ import '../base/common.dart';
 import '../base/logger.dart';
 import '../build_info.dart';
 import '../globals.dart';
-import '../runner/flutter_command.dart' show FlutterCommandResult;
+import '../runner/flutter_command.dart' show DevelopmentArtifact, FlutterCommandResult;
 import '../web/compile.dart';
 import 'build.dart';
 
@@ -19,6 +19,12 @@ class BuildWebCommand extends BuildSubCommand {
     defaultBuildMode = BuildMode.release;
   }
 
+  @override
+  Set<DevelopmentArtifact> get requiredArtifacts => const <DevelopmentArtifact>{
+    DevelopmentArtifact.universal,
+    DevelopmentArtifact.web,
+  };
+
   @override
   final String name = 'web';
 

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

@@ -245,7 +245,7 @@ class CreateCommand extends FlutterCommand {
       throwToolExit('Neither the --flutter-root command line flag nor the FLUTTER_ROOT environment '
         'variable was specified. Unable to find package:flutter.', exitCode: 2);
 
-    await Cache.instance.updateAll();
+    await Cache.instance.updateAll(<DevelopmentArtifact>{ DevelopmentArtifact.universal });
 
     final String flutterRoot = fs.path.absolute(Cache.flutterRoot);
 

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

@@ -223,7 +223,7 @@ class IdeConfigCommand extends FlutterCommand {
       throwToolExit('Currently, the only supported IDE is IntelliJ\n$usage', exitCode: 2);
     }
 
-    await Cache.instance.updateAll();
+    await Cache.instance.updateAll(<DevelopmentArtifact>{ DevelopmentArtifact.universal });
 
     if (argResults['update-templates']) {
       _handleTemplateUpdate();

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

@@ -4,6 +4,7 @@
 
 import 'dart:async';
 
+import '../cache.dart';
 import '../globals.dart';
 import '../runner/flutter_command.dart';
 
@@ -11,6 +12,12 @@ class PrecacheCommand extends FlutterCommand {
   PrecacheCommand() {
     argParser.addFlag('all-platforms', abbr: 'a', negatable: false,
         help: 'Precache artifacts for all platforms.');
+    argParser.addFlag('android', negatable: true, defaultsTo: true,
+        help: 'Precache artifacts for Android development');
+    argParser.addFlag('ios', negatable: true, defaultsTo: true,
+        help: 'Precache artifacts for iOS developemnt');
+    argParser.addFlag('web', negatable: true, defaultsTo: false,
+        help: 'Precache artifacts for web development');
   }
 
   @override
@@ -24,14 +31,25 @@ class PrecacheCommand extends FlutterCommand {
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    if (argResults['all-platforms'])
+    if (argResults['all-platforms']) {
       cache.includeAllPlatforms = true;
-
-    if (cache.isUpToDate())
+    }
+    final Set<DevelopmentArtifact> requiredArtifacts = <DevelopmentArtifact>{ DevelopmentArtifact.universal };
+    if (argResults['android']) {
+      requiredArtifacts.add(DevelopmentArtifact.android);
+    }
+    if (argResults['ios']) {
+      requiredArtifacts.add(DevelopmentArtifact.iOS);
+    }
+    if (argResults['web']) {
+      requiredArtifacts.add(DevelopmentArtifact.web);
+    }
+
+    if (cache.isUpToDate(requiredArtifacts)) {
       printStatus('Already up-to-date.');
-    else
-      await cache.updateAll();
-
+    } else {
+      await cache.updateAll(requiredArtifacts);
+    }
     return null;
   }
 }

packages/flutter_tools/lib/src/compile.dart

@@ -232,7 +232,6 @@ class KernelCompiler {
     if (fs.file('pubspec.yaml').existsSync()) {
       flutterProject = await FlutterProject.current();
     }
-    final FlutterEngine engine = FlutterEngine(cache);
 
     // TODO(cbracken): eliminate pathFilter.
     // Currently the compiler emits buildbot paths for the core libs in the
@@ -246,7 +245,7 @@ class KernelCompiler {
           'entryPoint': mainPath,
           'trackWidgetCreation': trackWidgetCreation.toString(),
           'linkPlatformKernelIn': linkPlatformKernelIn.toString(),
-          'engineHash': engine.version,
+          'engineHash': Cache.instance.engineRevision,
           'buildersUsed': '${flutterProject != null ? flutterProject.hasBuilders : false}',
         },
         depfilePaths: <String>[depFilePath],

packages/flutter_tools/lib/src/doctor.dart

@@ -170,9 +170,7 @@ class Doctor {
   }
 
   Future<bool> checkRemoteArtifacts(String engineRevision) async {
-    final Cache cache = Cache();
-    final FlutterEngine engine = FlutterEngine(cache);
-    return await engine.areRemoteArtifactsAvailable(engineVersion: engineRevision);
+    return Cache.instance.areRemoteArtifactsAvailable(engineVersion: engineRevision);
   }
 
   /// Print information about the state of installed tooling.

packages/flutter_tools/lib/src/runner/flutter_command.dart

@@ -19,6 +19,7 @@ import '../base/user_messages.dart';
 import '../base/utils.dart';
 import '../build_info.dart';
 import '../bundle.dart' as bundle;
+import '../cache.dart';
 import '../dart/package_map.dart';
 import '../dart/pub.dart';
 import '../device.dart';
@@ -28,6 +29,8 @@ import '../project.dart';
 import '../usage.dart';
 import 'flutter_command_runner.dart';
 
+export '../cache.dart' show DevelopmentArtifact;
+
 enum ExitStatus {
   success,
   warning,
@@ -530,8 +533,9 @@ abstract class FlutterCommand extends Command<void> {
 
     // Populate the cache. We call this before pub get below so that the sky_engine
     // package is available in the flutter cache for pub to find.
-    if (shouldUpdateCache)
-      await cache.updateAll();
+    if (shouldUpdateCache) {
+      await cache.updateAll(requiredArtifacts);
+    }
 
     if (shouldRunPub) {
       await pubGet(context: PubContext.getVerifyContext(name));
@@ -549,6 +553,16 @@ abstract class FlutterCommand extends Command<void> {
     return await runCommand();
   }
 
+  /// The set of development artifacts required for this command.
+  ///
+  /// Defaults to [DevelopmentArtifact.universal],
+  /// [DevelopmentArtifact.android], and [DevelopmentArtifact.iOS].
+  Set<DevelopmentArtifact> get requiredArtifacts => const <DevelopmentArtifact>{
+    DevelopmentArtifact.universal,
+    DevelopmentArtifact.iOS,
+    DevelopmentArtifact.android,
+  };
+
   /// Subclasses must implement this to execute the command.
   /// Optionally provide a [FlutterCommandResult] to send more details about the
   /// execution for analytics.

packages/flutter_tools/test/cache_test.dart

@@ -84,34 +84,34 @@ void main() {
     test('should not be up to date, if some cached artifact is not', () {
       final CachedArtifact artifact1 = MockCachedArtifact();
       final CachedArtifact artifact2 = MockCachedArtifact();
-      when(artifact1.isUpToDate()).thenReturn(true);
-      when(artifact2.isUpToDate()).thenReturn(false);
+      when(artifact1.isUpToDate(const <DevelopmentArtifact>{})).thenReturn(true);
+      when(artifact2.isUpToDate(const <DevelopmentArtifact>{})).thenReturn(false);
       final Cache cache = Cache(artifacts: <CachedArtifact>[artifact1, artifact2]);
-      expect(cache.isUpToDate(), isFalse);
+      expect(cache.isUpToDate(const <DevelopmentArtifact>{}), isFalse);
     });
     test('should be up to date, if all cached artifacts are', () {
       final CachedArtifact artifact1 = MockCachedArtifact();
       final CachedArtifact artifact2 = MockCachedArtifact();
-      when(artifact1.isUpToDate()).thenReturn(true);
-      when(artifact2.isUpToDate()).thenReturn(true);
+      when(artifact1.isUpToDate(const <DevelopmentArtifact>{})).thenReturn(true);
+      when(artifact2.isUpToDate(const <DevelopmentArtifact>{})).thenReturn(true);
       final Cache cache = Cache(artifacts: <CachedArtifact>[artifact1, artifact2]);
-      expect(cache.isUpToDate(), isTrue);
+      expect(cache.isUpToDate(const <DevelopmentArtifact>{}), isTrue);
     });
     test('should update cached artifacts which are not up to date', () async {
       final CachedArtifact artifact1 = MockCachedArtifact();
       final CachedArtifact artifact2 = MockCachedArtifact();
-      when(artifact1.isUpToDate()).thenReturn(true);
-      when(artifact2.isUpToDate()).thenReturn(false);
+      when(artifact1.isUpToDate(const <DevelopmentArtifact>{})).thenReturn(true);
+      when(artifact2.isUpToDate(const <DevelopmentArtifact>{})).thenReturn(false);
       final Cache cache = Cache(artifacts: <CachedArtifact>[artifact1, artifact2]);
-      await cache.updateAll();
+      await cache.updateAll(const <DevelopmentArtifact>{});
       verifyNever(artifact1.update());
       verify(artifact2.update());
     });
     testUsingContext('failed storage.googleapis.com download shows China warning', () async {
       final CachedArtifact artifact1 = MockCachedArtifact();
       final CachedArtifact artifact2 = MockCachedArtifact();
-      when(artifact1.isUpToDate()).thenReturn(false);
-      when(artifact2.isUpToDate()).thenReturn(false);
+      when(artifact1.isUpToDate(const <DevelopmentArtifact>{})).thenReturn(false);
+      when(artifact2.isUpToDate(const <DevelopmentArtifact>{})).thenReturn(false);
       final MockInternetAddress address = MockInternetAddress();
       when(address.host).thenReturn('storage.googleapis.com');
       when(artifact1.update()).thenThrow(SocketException(
@@ -120,7 +120,7 @@ void main() {
       ));
       final Cache cache = Cache(artifacts: <CachedArtifact>[artifact1, artifact2]);
       try {
-        await cache.updateAll();
+        await cache.updateAll(const <DevelopmentArtifact>{});
         fail('Mock thrown exception expected');
       } catch (e) {
         verify(artifact1.update());

packages/flutter_tools/test/runner/flutter_command_test.dart

@@ -42,7 +42,7 @@ void main() {
     testUsingContext('honors shouldUpdateCache true', () async {
       final DummyFlutterCommand flutterCommand = DummyFlutterCommand(shouldUpdateCache: true);
       await flutterCommand.run();
-      verify(cache.updateAll()).called(1);
+      verify(cache.updateAll(any)).called(1);
     },
     overrides: <Type, Generator>{
       Cache: () => cache,