Always use user-level pub cache (#121802)

Use the pub cache resolved by pub itself.
To add packages to the flutter.zip download they are packaged as tar.gz and added to the pub-cache on first run by using  `pub cache preload`.

.gitignore

@@ -51,7 +51,7 @@ analysis_benchmark.json
 .flutter-plugins-dependencies
 **/generated_plugin_registrant.dart
 .packages
-.pub-cache/
+.pub-preload-cache/
 .pub/
 build/
 flutter_*.png

bin/internal/shared.bat

@@ -22,8 +22,6 @@ SET script_path=%flutter_tools_dir%\bin\flutter_tools.dart
 SET dart_sdk_path=%cache_dir%\dart-sdk
 SET engine_stamp=%cache_dir%\engine-dart-sdk.stamp
 SET engine_version_path=%FLUTTER_ROOT%\bin\internal\engine.version
-SET pub_cache_path=%FLUTTER_ROOT%\.pub-cache
-
 SET dart=%dart_sdk_path%\bin\dart.exe
 
 REM Ensure that bin/cache exists.

bin/internal/shared.sh

@@ -149,9 +149,6 @@ function upgrade_flutter () (
       export PUB_SUMMARY_ONLY=1
     fi
     export PUB_ENVIRONMENT="$PUB_ENVIRONMENT:flutter_install"
-    if [[ -d "$FLUTTER_ROOT/.pub-cache" ]]; then
-      export PUB_CACHE="${PUB_CACHE:-"$FLUTTER_ROOT/.pub-cache"}"
-    fi
     pub_upgrade_with_retry
 
     # Move the old snapshot - we can't just overwrite it as the VM might currently have it

dev/bots/prepare_package.dart

@@ -8,11 +8,13 @@ import 'dart:io' hide Platform;
 import 'dart:typed_data';
 
 import 'package:args/args.dart';
+import 'package:convert/convert.dart';
 import 'package:crypto/crypto.dart';
 import 'package:crypto/src/digest_sink.dart';
 import 'package:http/http.dart' as http;
 import 'package:path/path.dart' as path;
 import 'package:platform/platform.dart' show LocalPlatform, Platform;
+import 'package:pool/pool.dart';
 import 'package:process/process.dart';
 
 const String gobMirror =
@@ -189,7 +191,7 @@ class ArchiveCreator {
       subprocessOutput: subprocessOutput,
       platform: platform,
     )..environment['PUB_CACHE'] = path.join(
-      flutterRoot.absolute.path, '.pub-cache',
+      tempDir.path, '.pub-cache',
     );
     final String flutterExecutable = path.join(
       flutterRoot.absolute.path,
@@ -426,6 +428,104 @@ class ArchiveCreator {
     await _unzipArchive(gitFile, workingDirectory: minGitPath);
   }
 
+  /// Downloads an archive of every package that is present in the temporary
+  /// pub-cache from pub.dev. Stores the archives in
+  /// $flutterRoot/.pub-preload-cache.
+  ///
+  /// These archives will be installed in the user-level cache on first
+  /// following flutter command that accesses the cache.
+  ///
+  /// Precondition: all packages currently in the PUB_CACHE of [_processRunner]
+  /// are installed from pub.dev.
+  Future<void> _downloadPubPackageArchives() async {
+    final Pool pool = Pool(10); // Number of simultaneous downloads.
+    final http.Client client = http.Client();
+    final Directory preloadCache = Directory(path.join(flutterRoot.path, '.pub-preload-cache'));
+    preloadCache.createSync(recursive: true);
+    /// Fetch a single package.
+    Future<void> fetchPackageArchive(String name, String version) async {
+      await pool.withResource(() async {
+        stderr.write('Fetching package archive for $name-$version.\n');
+        int retries = 7;
+        while (true) {
+          retries-=1;
+          try {
+            final Uri packageListingUrl =
+              Uri.parse('https://pub.dev/api/packages/$name');
+            // Fetch the package listing to obtain the package download url.
+            final http.Response packageListingResponse =
+                await client.get(packageListingUrl);
+            if (packageListingResponse.statusCode != 200) {
+              throw Exception('Downloading $packageListingUrl failed. Status code ${packageListingResponse.statusCode}.');
+            }
+            final dynamic decodedPackageListing = json.decode(packageListingResponse.body);
+            if (decodedPackageListing is! Map) {
+              throw const FormatException('Package listing should be a map');
+            }
+            final dynamic versions =  decodedPackageListing['versions'];
+            if (versions is! List) {
+              throw const FormatException('.versions should be a list');
+            }
+            final Map<String, dynamic> versionDescription = versions.firstWhere(
+              (dynamic description) {
+                if (description is! Map) {
+                  throw const FormatException('.versions elements should be maps');
+                }
+                return description['version'] == version;
+              },
+              orElse: () => throw FormatException('Could not find $name-$version in package listing')
+            ) as Map<String, dynamic>;
+            final dynamic downloadUrl = versionDescription['archive_url'];
+            if (downloadUrl is! String) {
+              throw const FormatException('archive_url should be a string');
+            }
+            final dynamic archiveSha256 = versionDescription['archive_sha256'];
+            if (archiveSha256 is! String) {
+              throw const FormatException('archive_sha256 should be a string');
+            }
+            final http.Request request = http.Request('get', Uri.parse(downloadUrl));
+            final http.StreamedResponse response = await client.send(request);
+            if (response.statusCode != 200) {
+              throw Exception('Downloading ${request.url} failed. Status code ${response.statusCode}.');
+            }
+            final File archiveFile = File(
+              path.join(preloadCache.path, '$name-$version.tar.gz'),
+            );
+            await response.stream.pipe(archiveFile.openWrite());
+            final Stream<List<int>> archiveStream = archiveFile.openRead();
+            final Digest r = await sha256.bind(archiveStream).first;
+            if (hex.encode(r.bytes) != archiveSha256) {
+              throw Exception('Hash mismatch of downloaded archive');
+            }
+          } on Exception catch (e) {
+            stderr.write('Failed downloading $name-$version. $e\n');
+            if (retries > 0) {
+              stderr.write('Retrying download of $name-$version...');
+              // Retry.
+              continue;
+            } else {
+              rethrow;
+            }
+          }
+          break;
+        }
+      });
+    }
+    final Map<String, dynamic> cacheDescription =
+        json.decode(await _runFlutter(<String>['pub', 'cache', 'list'])) as Map<String, dynamic>;
+    final Map<String, dynamic> packages = cacheDescription['packages'] as Map<String, dynamic>;
+    final List<Future<void>> downloads = <Future<void>>[];
+    for (final MapEntry<String, dynamic> package in packages.entries) {
+      final String name = package.key;
+      final Map<String, dynamic> versions = package.value as Map<String, dynamic>;
+      for (final String version in versions.keys) {
+        downloads.add(fetchPackageArchive(name, version));
+      }
+    }
+    await Future.wait(downloads);
+    client.close();
+  }
+
   /// Prepare the archive repo so that it has all of the caches warmed up and
   /// is configured for the user to begin working.
   Future<void> _populateCaches() async {
@@ -446,7 +546,7 @@ class ArchiveCreator {
         workingDirectory: tempDir,
       );
     }
-
+    await _downloadPubPackageArchives();
     // Yes, we could just skip all .packages files when constructing
     // the archive, but some are checked in, and we don't want to skip
     // those.
@@ -795,8 +895,8 @@ class ArchivePublisher {
   }
 }
 
-/// Prepares a flutter git repo to be packaged up for distribution.
-/// It mainly serves to populate the .pub-cache with any appropriate Dart
+/// Prepares a flutter git repo to be packaged up for distribution. It mainly
+/// serves to populate the .pub-preload-cache with any appropriate Dart
 /// packages, and the flutter cache in bin/cache with the appropriate
 /// dependencies and snapshots.
 ///

dev/bots/test/prepare_package_test.dart

@@ -143,6 +143,7 @@ void main() {
           '$flutter create --template=app ${createBase}app': null,
           '$flutter create --template=package ${createBase}package': null,
           '$flutter create --template=plugin ${createBase}plugin': null,
+          '$flutter pub cache list': <ProcessResult>[ProcessResult(0,0,'{"packages":{}}','')],
           'git clean -f -x -- **/.packages': null,
           'git clean -f -x -- **/.dart_tool/': null,
           if (platform.isMacOS) 'codesign -vvvv --check-notarization ${path.join(tempDir.path, 'flutter', 'bin', 'cache', 'dart-sdk', 'bin', 'dart')}': null,
@@ -180,6 +181,7 @@ void main() {
           '$flutter create --template=app ${createBase}app': null,
           '$flutter create --template=package ${createBase}package': null,
           '$flutter create --template=plugin ${createBase}plugin': null,
+          '$flutter pub cache list': <ProcessResult>[ProcessResult(0,0,'{"packages":{}}','')],
           'git clean -f -x -- **/.packages': null,
           'git clean -f -x -- **/.dart_tool/': null,
           if (platform.isMacOS) 'codesign -vvvv --check-notarization ${path.join(tempDir.path, 'flutter', 'bin', 'cache', 'dart-sdk', 'bin', 'dart')}': null,
@@ -228,6 +230,7 @@ void main() {
           '$flutter create --template=app ${createBase}app': null,
           '$flutter create --template=package ${createBase}package': null,
           '$flutter create --template=plugin ${createBase}plugin': null,
+          '$flutter pub cache list': <ProcessResult>[ProcessResult(0,0,'{"packages":{}}','')],
           'git clean -f -x -- **/.packages': null,
           'git clean -f -x -- **/.dart_tool/': null,
           if (platform.isMacOS) 'codesign -vvvv --check-notarization ${path.join(tempDir.path, 'flutter', 'bin', 'cache', 'dart-sdk', 'bin', 'dart')}': null,
@@ -286,6 +289,7 @@ void main() {
           '$flutter create --template=app ${createBase}app': null,
           '$flutter create --template=package ${createBase}package': null,
           '$flutter create --template=plugin ${createBase}plugin': null,
+          '$flutter pub cache list': <ProcessResult>[ProcessResult(0,0,'{"packages":{}}','')],
           'git clean -f -x -- **/.packages': null,
           'git clean -f -x -- **/.dart_tool/': null,
           if (platform.isWindows) 'attrib -h .git': null,
@@ -336,6 +340,7 @@ void main() {
           '$flutter create --template=app ${createBase}app': null,
           '$flutter create --template=package ${createBase}package': null,
           '$flutter create --template=plugin ${createBase}plugin': null,
+          '$flutter pub cache list': <ProcessResult>[ProcessResult(0,0,'{"packages":{}}','')],
           'git clean -f -x -- **/.packages': null,
           'git clean -f -x -- **/.dart_tool/': null,
           if (platform.isMacOS) 'codesign -vvvv --check-notarization $binPath': <ProcessResult>[codesignFailure],

packages/flutter_tools/lib/src/dart/pub.dart

@@ -34,39 +34,29 @@ const String _kPubCacheEnvironmentKey = 'PUB_CACHE';
 
 typedef MessageFilter = String? Function(String message);
 
-/// globalCachePath is the directory in which the content of the localCachePath will be moved in
-void joinCaches({
-  required FileSystem fileSystem,
-  required Directory globalCacheDirectory,
-  required Directory dependencyDirectory,
+/// Load any package-files stored in [preloadCacheDir] into the pub cache if it
+/// exists.
+///
+/// Deletes the [preloadCacheDir].
+@visibleForTesting
+void preloadPubCache({
+  required Directory preloadCacheDir,
+  required ProcessManager processManager,
+  required Logger logger,
+  required List<String> pubCommand,
 }) {
-  for (final FileSystemEntity entity in dependencyDirectory.listSync()) {
-    final String newPath = fileSystem.path.join(globalCacheDirectory.path, entity.basename);
-    if (entity is File) {
-      if (!fileSystem.file(newPath).existsSync()) {
-        entity.copySync(newPath);
-      }
-    } else if (entity is Directory) {
-      if (!globalCacheDirectory.childDirectory(entity.basename).existsSync()) {
-        final Directory newDirectory = globalCacheDirectory.childDirectory(entity.basename);
-        newDirectory.createSync();
-        joinCaches(
-          fileSystem: fileSystem,
-          globalCacheDirectory: newDirectory,
-          dependencyDirectory: entity,
-        );
-      }
-    }
+  if (preloadCacheDir.existsSync()) {
+    final Iterable<String> cacheFiles =
+          preloadCacheDir
+            .listSync()
+            .map((FileSystemEntity f) => f.path)
+            .where((String path) => path.endsWith('.tar.gz'));
+    processManager.runSync(<String>[...pubCommand, 'cache', 'preload',...cacheFiles]);
+    _tryDeleteDirectory(preloadCacheDir, logger);
   }
 }
 
-Directory createDependencyDirectory(Directory pubGlobalDirectory, String dependencyName) {
-  final Directory newDirectory = pubGlobalDirectory.childDirectory(dependencyName);
-  newDirectory.createSync();
-  return newDirectory;
-}
-
-bool tryDelete(Directory directory, Logger logger) {
+bool _tryDeleteDirectory(Directory directory, Logger logger) {
   try {
     if (directory.existsSync()) {
       directory.deleteSync(recursive: true);
@@ -78,24 +68,6 @@ bool tryDelete(Directory directory, Logger logger) {
   return true;
 }
 
-/// When local cache (flutter_root/.pub-cache) and global cache (HOME/.pub-cache) are present a
-/// merge needs to be done leaving only the global
-///
-/// Valid pubCache should look like this ./localCachePath/.pub-cache/hosted/pub.dartlang.org
-bool needsToJoinCache({
-  required FileSystem fileSystem,
-  required String localCachePath,
-  required Directory? globalDirectory,
-}) {
-  if (globalDirectory == null) {
-    return false;
-  }
-  final Directory localDirectory = fileSystem.directory(localCachePath);
-
-  return globalDirectory.childDirectory('hosted').childDirectory('pub.dartlang.org').existsSync() &&
-    localDirectory.childDirectory('hosted').childDirectory('pub.dartlang.org').existsSync();
-}
-
 /// Represents Flutter-specific data that is added to the `PUB_ENVIRONMENT`
 /// environment variable and allows understanding the type of requests made to
 /// the package site on Flutter's behalf.
@@ -402,7 +374,7 @@ class _DefaultPub implements Pub {
   }) async {
     int exitCode;
 
-    final List<String> pubCommand = _pubCommand(arguments);
+    final List<String> pubCommand = <String>[..._pubCommand, ...arguments];
     final Map<String, String> pubEnvironment = await _createPubEnvironment(context: context, flutterRootOverride: flutterRootOverride, summaryOnly: outputMode == PubOutputMode.summaryOnly);
 
     try {
@@ -536,7 +508,7 @@ class _DefaultPub implements Pub {
       arguments.insert(0, '--trace');
     }
     final Map<String, String> pubEnvironment = await _createPubEnvironment(context: context, flutterRootOverride: flutterRootOverride);
-    final List<String> pubCommand = _pubCommand(arguments);
+    final List<String> pubCommand = <String>[..._pubCommand, ...arguments];
     final int code = await _processUtils.stream(
         pubCommand,
         workingDirectory: directory,
@@ -590,7 +562,9 @@ class _DefaultPub implements Pub {
   }
 
   /// The command used for running pub.
-  List<String> _pubCommand(List<String> arguments) {
+  late final List<String> _pubCommand = _computePubCommand();
+
+  List<String> _computePubCommand() {
     // TODO(zanderso): refactor to use artifacts.
     final String sdkPath = _fileSystem.path.joinAll(<String>[
       Cache.flutterRoot!,
@@ -607,7 +581,7 @@ class _DefaultPub implements Pub {
         'permissions for the current user.'
       );
     }
-    return <String>[sdkPath, '--no-analytics', 'pub', ...arguments];
+    return <String>[sdkPath, '--no-analytics', 'pub'];
   }
 
   // Returns the environment value that should be used when running pub.
@@ -629,88 +603,26 @@ class _DefaultPub implements Pub {
     return values.join(':');
   }
 
-  /// There are 3 ways to get the pub cache location
+  /// There are 2 ways to get the pub cache location
   ///
   /// 1) Provide the _kPubCacheEnvironmentKey.
-  /// 2) There is a local cache (in the Flutter SDK) but not a global one (in the user's home directory).
-  /// 3) If both local and global are available then merge the local into global and return the global.
+  /// 2) The pub default user-level pub cache.
+  ///
+  /// If we are using 2, check if there are pre-packaged packages in
+  /// $FLUTTER_ROOT/.pub-preload-cache and install them in the user-level cache.
   String? _getPubCacheIfAvailable() {
     if (_platform.environment.containsKey(_kPubCacheEnvironmentKey)) {
       return _platform.environment[_kPubCacheEnvironmentKey];
     }
 
-    final String localCachePath = _fileSystem.path.join(Cache.flutterRoot!, '.pub-cache');
-    final Directory? globalDirectory;
-    if (_platform.isWindows) {
-      globalDirectory = _getWindowsGlobalDirectory;
-    }
-    else {
-      if (_platform.environment['HOME'] == null) {
-        globalDirectory = null;
-      } else {
-        final String homeDirectoryPath = _platform.environment['HOME']!;
-        globalDirectory = _fileSystem.directory(_fileSystem.path.join(homeDirectoryPath, '.pub-cache'));
-      }
-    }
-
-    if (needsToJoinCache(
-      fileSystem: _fileSystem,
-      localCachePath: localCachePath,
-      globalDirectory: globalDirectory,
-    )) {
-      final Directory localDirectoryPub = _fileSystem.directory(
-        _fileSystem.path.join(localCachePath, 'hosted', 'pub.dartlang.org')
-      );
-      final Directory globalDirectoryPub = _fileSystem.directory(
-        _fileSystem.path.join(globalDirectory!.path, 'hosted', 'pub.dartlang.org')
-      );
-      for (final FileSystemEntity entity in localDirectoryPub.listSync()) {
-        if (entity is Directory && !globalDirectoryPub.childDirectory(entity.basename).existsSync()){
-          try {
-            final Directory newDirectory = createDependencyDirectory(globalDirectoryPub, entity.basename);
-            joinCaches(
-              fileSystem: _fileSystem,
-              globalCacheDirectory: newDirectory,
-              dependencyDirectory: entity,
-            );
-          } on FileSystemException {
-            if (!tryDelete(globalDirectoryPub.childDirectory(entity.basename), _logger)) {
-              _logger.printWarning('The join of pub-caches failed');
-              _logger.printStatus('Running "dart pub cache repair"');
-              _processManager.runSync(<String>['dart', 'pub', 'cache', 'repair']);
-            }
-          }
-        }
-      }
-      tryDelete(_fileSystem.directory(localCachePath), _logger);
-      return globalDirectory.path;
-    } else if (globalDirectory != null && globalDirectory.existsSync()) {
-      return globalDirectory.path;
-    } else if (_fileSystem.directory(localCachePath).existsSync()) {
-      return localCachePath;
-    }
+    final String flutterRootPath = Cache.flutterRoot!;
+    final Directory flutterRoot = _fileSystem.directory(flutterRootPath);
+    final Directory preloadCacheDir = flutterRoot.childDirectory('.pub-preload-cache');
+    preloadPubCache(preloadCacheDir: preloadCacheDir,logger: _logger,processManager: _processManager, pubCommand: _pubCommand);
     // Use pub's default location by returning null.
     return null;
   }
 
-  Directory? get _getWindowsGlobalDirectory {
-    // %LOCALAPPDATA% is preferred as the cache location over %APPDATA%, because the latter is synchronised between
-    // devices when the user roams between them, whereas the former is not.
-    // The default cache dir used to be in %APPDATA%, so to avoid breaking old installs,
-    // we use the old dir in %APPDATA% if it exists. Else, we use the new default location
-    // in %LOCALAPPDATA%.
-    for (final String envVariable in <String>['APPDATA', 'LOCALAPPDATA']) {
-      if (_platform.environment[envVariable] != null) {
-        final String homePath = _platform.environment[envVariable]!;
-        final Directory globalDirectory = _fileSystem.directory(_fileSystem.path.join(homePath, 'Pub', 'Cache'));
-        if (globalDirectory.existsSync()) {
-          return globalDirectory;
-        }
-      }
-    }
-    return null;
-  }
-
   /// The full environment used when running pub.
   ///
   /// [context] provides extra information to package server requests to

packages/flutter_tools/test/general.shard/base/pub_join_caches_test.dart

-// Copyright 2014 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-import 'package:file/file.dart';
-import 'package:file/memory.dart';
-import 'package:flutter_tools/src/base/file_system.dart';
-import 'package:flutter_tools/src/dart/pub.dart';
-
-import '../../src/common.dart';
-
-void main() {
-  testWithoutContext('join two folders', () async {
-    final MemoryFileSystem fileSystem = MemoryFileSystem();
-    final Directory target = fileSystem.currentDirectory.childDirectory('target');
-    final Directory extra = fileSystem.currentDirectory.childDirectory('extra');
-    target.createSync();
-    target.childFile('first.file').createSync();
-    target.childDirectory('dir').createSync();
-
-    extra.createSync();
-    extra.childFile('second.file').writeAsBytesSync(<int>[0]);
-    extra.childDirectory('dir').createSync();
-    extra.childDirectory('dir').childFile('third.file').writeAsBytesSync(<int>[0]);
-    extra.childDirectory('dir_2').createSync();
-    extra.childDirectory('dir_2').childFile('fourth.file').writeAsBytesSync(<int>[0]);
-    extra.childDirectory('dir_3').createSync();
-    extra.childDirectory('dir_3').childFile('fifth.file').writeAsBytesSync(<int>[0]);
-    joinCaches(
-      fileSystem: fileSystem,
-      globalCacheDirectory: target,
-      dependencyDirectory: extra,
-    );
-
-    expect(target.childFile('second.file').existsSync(), true);
-    expect(target.childDirectory('dir').childFile('third.file').existsSync(), false);
-    expect(target.childDirectory('dir_2').childFile('fourth.file').existsSync(), true);
-    expect(target.childDirectory('dir_3').childFile('fifth.file').existsSync(), true);
-    expect(extra.childDirectory('dir').childFile('third.file').existsSync(), true);
-  });
-
-  group('needsToJoinCache()', (){
-    testWithoutContext('make join', () async {
-      final MemoryFileSystem fileSystem = MemoryFileSystem();
-      final Directory local = fileSystem.currentDirectory.childDirectory('local');
-      final Directory global = fileSystem.currentDirectory.childDirectory('global');
-
-      for (final Directory directory in <Directory>[local, global]) {
-        directory.createSync();
-        directory.childDirectory('hosted').createSync();
-        directory.childDirectory('hosted').childDirectory('pub.dartlang.org').createSync();
-      }
-      final bool pass = needsToJoinCache(
-        fileSystem: fileSystem,
-        localCachePath: local.path,
-        globalDirectory: global,
-      );
-      expect(pass, true);
-    });
-
-    testWithoutContext('detects when global pub-cache does not have a pub.dartlang.org dir', () async {
-      final MemoryFileSystem fileSystem = MemoryFileSystem();
-      final Directory local = fileSystem.currentDirectory.childDirectory('local');
-      final Directory global = fileSystem.currentDirectory.childDirectory('global');
-      local.createSync();
-      global.createSync();
-      local.childDirectory('hosted').createSync();
-      local.childDirectory('hosted').childDirectory('pub.dartlang.org').createSync();
-
-      expect(
-        needsToJoinCache(
-          fileSystem: fileSystem,
-          localCachePath: local.path,
-          globalDirectory: global
-        ),
-        false
-      );
-    });
-    testWithoutContext("don't join global directory null", () async {
-      final MemoryFileSystem fileSystem = MemoryFileSystem();
-      final Directory local = fileSystem.currentDirectory.childDirectory('local');
-      const Directory? global = null;
-      local.createSync();
-      local.childDirectory('hosted').createSync();
-      local.childDirectory('hosted').childDirectory('pub.dartlang.org').createSync();
-
-      expect(
-        needsToJoinCache(
-          fileSystem: fileSystem,
-          localCachePath: local.path,
-          globalDirectory: global
-        ),
-        false
-      );
-    });
-  });
-}

packages/flutter_tools/test/general.shard/dart/pub_get_test.dart

@@ -757,29 +757,24 @@ exit code: 66
     expect(processManager, hasNoRemainingExpectations);
   });
 
-  testWithoutContext('pub cache local is merge to global', () async {
+  testWithoutContext('Preloaded packages are added to the pub cache', () async {
     final FileSystem fileSystem = MemoryFileSystem.test();
-    final Directory local = fileSystem.currentDirectory.childDirectory('.pub-cache');
-    final Directory global = fileSystem.currentDirectory.childDirectory('/global');
-    global.createSync();
-    for (final Directory dir in <Directory>[global.childDirectory('.pub-cache'), local]) {
-      dir.createSync();
-      dir.childDirectory('hosted').createSync();
-      dir.childDirectory('hosted').childDirectory('pub.dartlang.org').createSync();
-    }
-
-    final Directory globalHosted = global.childDirectory('.pub-cache').childDirectory('hosted').childDirectory('pub.dartlang.org');
-    globalHosted.childFile('first.file').createSync();
-    globalHosted.childDirectory('dir').createSync();
-
-    final Directory localHosted = local.childDirectory('hosted').childDirectory('pub.dartlang.org');
-    localHosted.childFile('second.file').writeAsBytesSync(<int>[0]);
-    localHosted.childDirectory('dir').createSync();
-    localHosted.childDirectory('dir').childFile('third.file').writeAsBytesSync(<int>[0]);
-    localHosted.childDirectory('dir_2').createSync();
-    localHosted.childDirectory('dir_2').childFile('fourth.file').writeAsBytesSync(<int>[0]);
+    final Directory preloadCache = fileSystem.currentDirectory.childDirectory('.pub-preload-cache');
+    preloadCache.childFile('a.tar.gz').createSync(recursive: true);
+    preloadCache.childFile('b.tar.gz').createSync();
 
     final FakeProcessManager processManager = FakeProcessManager.list(<FakeCommand>[
+      const FakeCommand(
+        command: <String>[
+          'bin/cache/dart-sdk/bin/dart',
+          '--no-analytics',
+          'pub',
+          'cache',
+          'preload',
+          '.pub-preload-cache/a.tar.gz',
+          '.pub-preload-cache/b.tar.gz',
+        ],
+      ),
       const FakeCommand(
         command: <String>[
           'bin/cache/dart-sdk/bin/dart',
@@ -793,7 +788,6 @@ exit code: 66
         exitCode: 69,
         environment: <String, String>{
           'FLUTTER_ROOT': '',
-          'PUB_CACHE': '/global/.pub-cache',
           'PUB_ENVIRONMENT': 'flutter_cli:flutter_tests',
         },
       ),
@@ -822,12 +816,7 @@ exit code: 66
     }
 
     expect(processManager, hasNoRemainingExpectations);
-    expect(local.existsSync(), false);
-    expect(globalHosted.childFile('second.file').existsSync(), false);
-    expect(
-        globalHosted.childDirectory('dir').childFile('third.file').existsSync(), false
-    ); // do not copy dependencies that are already downloaded
-    expect(globalHosted.childDirectory('dir_2').childFile('fourth.file').existsSync(), true);
+    expect(preloadCache.existsSync(), false);
   });
 
   testWithoutContext('pub cache in environment is used', () async {