Allow third-party tools to resolve dependencies

lib/src/command.dart

@@ -69,7 +69,12 @@ abstract class PubCommand extends Command<int> {
   ///
   /// This will load the pubspec and fail with an error if the current directory
   /// is not a package.
-  late final Entrypoint entrypoint = Entrypoint(directory, cache);
+  late final Entrypoint entrypoint =
+      Entrypoint(directory, cache, allowThirdPartyTool: allowThirdPartyTool);
+
+  /// Whether to skip up-to-date checks of dependency files, when generated by a
+  /// third party tool.
+  bool get allowThirdPartyTool => false;
 
   /// The URL for web documentation for this command.
   String? get docUrl => null;

lib/src/command/run.dart

@@ -25,6 +25,8 @@ class RunCommand extends PubCommand {
   bool get allowTrailingOptions => false;
   @override
   bool get hidden => deprecated;
+  @override
+  bool get allowThirdPartyTool => true;
 
   final bool deprecated;
   final bool alwaysUseSubprocess;

lib/src/entrypoint.dart

@@ -84,6 +84,13 @@ class Entrypoint {
   /// Whether this is an entrypoint for a globally-activated package.
   final bool isGlobal;
 
+  /// Whether to skip up-to-date checks of dependency files, when generated by a
+  /// third party tool.
+  ///
+  /// If `package_config.json` has as a `generator` other than `pub`, checks of
+  /// it, `.packages` and `pubspec.lock` are skipped.
+  final bool allowThirdPartyTool;
+
   /// The lockfile for the entrypoint.
   ///
   /// If not provided to the entrypoint, it will be loaded lazily from disk.
@@ -173,15 +180,16 @@ class Entrypoint {
   String get _incrementalDillsPath => p.join(cachePath, 'incremental');
 
   /// Loads the entrypoint from a package at [rootDir].
-  Entrypoint(String rootDir, this.cache)
+  Entrypoint(String rootDir, this.cache, {this.allowThirdPartyTool = false})
       : root = Package.load(null, rootDir, cache.sources),
         isGlobal = false;
 
   /// Creates an entrypoint given package and lockfile objects.
   /// If a SolveResult is already created it can be passed as an optimization.
   Entrypoint.global(this.root, this._lockFile, this.cache,
       {SolveResult? solveResult})
-      : isGlobal = true {
+      : isGlobal = true,
+        allowThirdPartyTool = false {
     if (solveResult != null) {
       _packageGraph = PackageGraph.fromSolveResult(this, solveResult);
     }
@@ -506,6 +514,26 @@ class Entrypoint {
       );
     }
 
+    if (allowThirdPartyTool) {
+      // Check if a third party tool generated `package_config.json`.
+      var packageConfigText = readTextFile(packageConfigFile);
+      var packageConfigIsFromThirdParty =
+          !packageConfigText.contains('\n  "generator": "pub",\n');
+
+      if (packageConfigIsFromThirdParty) {
+        // Skip all checks of dependency files. This allows third party tools to
+        // resolve dependencies.
+        final generator = RegExp(r'"generator":\s*"([^"]+)",')
+                .firstMatch(packageConfigText)
+                ?.group(1) ??
+            '<unknown>';
+        log.message(
+          'Skipping dependency up-to-date checks: resolved by $generator tool.',
+        );
+        return;
+      }
+    }
+
     // Manually parse the lockfile because a full YAML parse is relatively slow
     // and this is on the hot path for "pub run".
     var lockFileText = readTextFile(lockFilePath);

lib/src/executable.dart

@@ -92,10 +92,6 @@ Future<int> runExecutable(
   }
 
   if (useSnapshot) {
-    // Since we don't access the package graph, this doesn't happen
-    // automatically.
-    entrypoint.assertUpToDate();
-
     if (!fileExists(snapshotPath) ||
         entrypoint.packageGraph.isPackageMutable(package)) {
       await recompile(executable);
@@ -298,7 +294,11 @@ Future<DartExecutableWithPackageConfig> getExecutableForCommand(
         'Could not find file `$descriptor`',
         CommandResolutionIssue.fileNotFound);
   }
-  final entrypoint = Entrypoint(root, SystemCache(rootDir: pubCacheDir));
+  final entrypoint = Entrypoint(
+    root,
+    SystemCache(rootDir: pubCacheDir),
+    allowThirdPartyTool: true,
+  );
   try {
     // TODO(sigurdm): it would be nicer with a 'isUpToDate' function.
     entrypoint.assertUpToDate();

test/descriptor.dart

@@ -279,8 +279,9 @@ Descriptor packagesFile([Map<String, String> dependencies]) =>
 Descriptor packageConfigFile(
   List<PackageConfigEntry> packages, {
   String generatorVersion = '0.1.2+3',
+  String generator = 'pub',
 }) =>
-    PackageConfigFileDescriptor(packages, generatorVersion);
+    PackageConfigFileDescriptor(packages, generatorVersion, generator);
 
 /// Create a [PackageConfigEntry] which assumes package with [name] is either
 /// a cached package with given [version] or a path dependency at given [path].

test/descriptor/packages.dart

@@ -106,6 +106,7 @@ class PackagesFileDescriptor extends Descriptor {
 /// Describes a `.dart_tools/package_config.json` file and its contents.
 class PackageConfigFileDescriptor extends Descriptor {
   final String _generatorVersion;
+  final String _generator;
 
   /// A map describing the packages in this `package_config.json` file.
   final List<PackageConfigEntry> _packages;
@@ -115,7 +116,7 @@ class PackageConfigFileDescriptor extends Descriptor {
       configVersion: 2,
       packages: _packages,
       generatorVersion: Version.parse(_generatorVersion),
-      generator: 'pub',
+      generator: _generator,
       generated: DateTime.now().toUtc(),
     );
   }
@@ -124,7 +125,8 @@ class PackageConfigFileDescriptor extends Descriptor {
   ///
   /// [dependencies] maps package names to strings describing where the packages
   /// are located on disk.
-  PackageConfigFileDescriptor(this._packages, this._generatorVersion)
+  PackageConfigFileDescriptor(
+      this._packages, this._generatorVersion, this._generator)
       : super('.dart_tool/package_config.json');
 
   @override

test/run/allows_third_part_tool_test.dart

@@ -0,0 +1,52 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// @dart=2.10
+
+import 'package:test/test.dart';
+
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+
+void main() {
+  test('allows a third party tool to resolve dependencies', () async {
+    await d.dir('local_baz', [
+      d.pubspec({'name': 'baz'}),
+    ]).create();
+
+    await d.dir(appPath, [
+      d.pubspec({
+        'name': 'myapp',
+        'dependencies': {
+          // Path dependencies trigger checks of all dependency files and
+          // is what third party tools, such as melos, use to link up packages
+          // for local development.
+          'baz': {'path': '../local_baz'},
+        },
+      }),
+      d.libDir('myapp'),
+    ]).create();
+
+    // Run pub.get to generate the dependency files.
+    await pubGet();
+
+    // Simulate a third party tool, modifying `package_config.json`.
+    var thirdPartyToolFile = d.dir(appPath, [
+      d.packageConfigFile([], generator: 'not-pub'),
+    ]);
+    await thirdPartyToolFile.create();
+    await thirdPartyToolFile.validate();
+
+    // Run the app with pub.run.
+    final pub = await pubRun(args: ['lib/myapp.dart']);
+    expect(
+      pub.stdoutStream(),
+      emits('Skipping dependency up-to-date checks: resolved by not-pub tool.'),
+    );
+    await pub.shouldExit(0);
+
+    // Validate that the file was not overwritten.
+    await thirdPartyToolFile.validate();
+  });
+}