Support removing dead packages with `pub install`.

utils/pub/entrypoint.dart

Index: utils/pub/entrypoint.dart
diff --git a/utils/pub/entrypoint.dart b/utils/pub/entrypoint.dart
index 32dbb612180244f16a17a2f00b00965bb7f28d64..d7e17ab493df0f1d3fe9322f6d7f0304cfe16a98 100644
--- a/utils/pub/entrypoint.dart
+++ b/utils/pub/entrypoint.dart
@@ -143,10 +143,12 @@ class Entrypoint {
    * [LockFile].
    */
   Future _installDependencies(List<PackageId> packageVersions) {
-    return Futures.wait(packageVersions.map((id) {
-      if (id.source is RootSource) return new Future.immediate(id);
-      return install(id);
-    })).chain(_saveLockFile).chain(_installSelfReference);
+    return _removeUnusedDependencies(packageVersions).chain((_) {
+      return Futures.wait(packageVersions.map((id) {
+        if (id.source is RootSource) return new Future.immediate(id);
+        return install(id);
+      }));
+    }).chain(_saveLockFile).chain(_installSelfReference);
   }
 
   /**
@@ -180,6 +182,27 @@ class Entrypoint {
   }
 
   /**
+   * Removes all dependencies that are no longer depended on from the `packages`
+   * directory. [packageIds] is a list of all packages that are still depended
+   * on.
+   */
+  Future _removeUnusedDependencies(List<PackageId> packageIds) {
+    var dependenciesToKeep = packageIds.map((id) => id.name);
+
+    return dirExists(path).chain((exists) {
+      if (exists) return listDir(path);
+      return new Future.immediate([]);
+    }).chain((existingDependencies) {
+      existingDependencies = existingDependencies.map(basename);
+      var dependenciesToRemove =
+        new List.from(setMinus(existingDependencies, dependenciesToKeep));

[Bob Nystrom, 2012/08/25 00:13:30]

Indent +2.

[nweiz, 2012/08/25 00:17:49]

Done.

+      return Futures.wait(dependenciesToRemove.map((dependency) {
+        return deleteDir(join(path, dependency));
+      }));
+    });
+  }
+
+  /**
    * Saves a list of concrete package versions to the `pubspec.lock` file.
    */
   Future _saveLockFile(List<PackageId> packageIds) {