Support removing dead packages with `pub install`.

utils/tests/pub/test_pub.dart

 // Copyright (c) 2012, 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.
 
 /**
  * Test infrastructure for testing pub. Unlike typical unit tests, most pub
  * tests are integration tests that stage some stuff on the file system, run
  * pub, and then validate the results. This library provides an API to build
  * tests like that.
  */
@@ skipping 38 matching lines @@
 GitRepoDescriptor git(Pattern name, [List<Descriptor> contents]) =>
     new GitRepoDescriptor(name, contents);
 
 /**
  * Creates a new [TarFileDescriptor] with [name] and [contents].
  */
 TarFileDescriptor tar(Pattern name, [List<Descriptor> contents]) =>
     new TarFileDescriptor(name, contents);
 
 /**
+ * Creates a new [NothingDescriptor] with [name].
+ */
+NothingDescriptor nothing(String name) => new NothingDescriptor(name);
+
+/**
  * The current [HttpServer] created using [serve].
  */
 var _server;
 
 /** The cached value for [_portCompleter]. */
 Completer<int> _portCompleterCache;
 
 /** The completer for [port]. */
 Completer<int> get _portCompleter {
   if (_portCompleterCache != null) return _portCompleterCache;
@@ skipping 225 matching lines @@
   if (modifier != null) value = "$name $modifier";
   return dir(new RegExp("$name${@'-[a-f0-9]+'}"), [
     file('$name.dart', 'main() => "$value";')
   ]);
 }
 
 /**
  * Describes the `packages/` directory containing all the given [packages],
  * which should be name/version pairs. The packages will be validated against
  * the format produced by the mock package server.
+ *
+ * A package with a null version should not be installed.
  */
 DirectoryDescriptor packagesDir(Map<String, String> packages) {
   var contents = <Descriptor>[];
   packages.forEach((name, version) {
-    contents.add(packageDir(name, version));
+    if (version == null) {
+      contents.add(nothing(name));
+    } else {
+      contents.add(packageDir(name, version));
+    }
   });
   return dir(packagesPath, contents);
 }
 
 /**
  * Describes the global package cache directory containing all the given
  * [packages], which should be name/version pairs. The packages will be
  * validated against the format produced by the mock package server.
  *
  * A package's value may also be a list of versions, in which case all versions
@@ skipping 696 matching lines @@
     }).then((tar) {
       var sourceStream = tar.openInputStream();
       pipeInputToInput(
           sourceStream, sinkStream, onClosed: tempDir.deleteRecursively);
     });
     return sinkStream;
   }
 }
 
 /**
+ * A descriptor that validates that no file exists with the given name.
+ */
+class NothingDescriptor extends Descriptor {
+  NothingDescriptor(String name) : super(name);
+
+  Future create(dir) => new Future.immediate(null);
+  Future delete(dir) => new Future.immediate(null);
+
+  Future validate(String dir) {
+    return exists(join(dir, name)).transform((exists) {
+      if (exists) Expect.fail('File $name in $dir should not exist.');
+    });
+  }
+
+  InputStream load(List<String> path) {
+    if (path.isEmpty()) {
+      throw "Can't load the contents of $name: it doesn't exist.";
+    } else {
+      throw "Can't load ${Strings.join(path, '/')} from within $name: $name "
+        "doesn't exist.";
+    }
+  }
+}
+
+/**
  * Takes a simple data structure (composed of [Map]s, [List]s, scalar objects,
  * and [Future]s) and recursively resolves all the [Future]s contained within.
  * Completes with the fully resolved structure.
  */
 Future _awaitObject(object) {
   // Unroll nested futures.
   if (object is Future) return object.chain(_awaitObject);
   if (object is Collection) return Futures.wait(object.map(_awaitObject));
   if (object is! Map) return new Future.immediate(object);
 
@@ skipping 20 matching lines @@
 }
 
 /**
  * Schedules a callback to be called after Pub is run with [runPub], even if it
  * fails.
  */
 void _scheduleCleanup(_ScheduledEvent event) {
   if (_scheduledCleanup == null) _scheduledCleanup = [];
   _scheduledCleanup.add(event);
 }