Handle a failure in "pub list-package-dirs".

pkg/analysis_server/lib/src/package_map_provider.dart

 // 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.
 
 library package.map.provider;
 
 import 'dart:convert';
 import 'dart:io' as io;
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/resource.dart';
 import 'package:analyzer/src/generated/engine.dart';
+import 'package:path/path.dart';
 
 /**
  * A PackageMapProvider is an entity capable of determining the mapping from
  * package name to source directory for a given folder.
  */
 abstract class PackageMapProvider {
   /**
    * Compute a package map for the given folder, if possible.
    *
-   * If a package map can't be computed, return null.
+   * If a package map can't be computed (e.g. because an error occurred), a
+   * [PackageMapInfo] will still be returned, but its packageMap will be null.
    */
   PackageMapInfo computePackageMap(Folder folder);
 }
 
 /**
  * Data structure output by PackageMapProvider.  This contains both the package
  * map and dependency information.
  */
 class PackageMapInfo {
   /**
    * The package map itself.  This is a map from package name to a list of
    * the folders containing source code for the package.
+   *
+   * `null` if an error occurred.
    */
   Map<String, List<Folder>> packageMap;
 
   /**
    * Dependency information.  This is a set of the paths which were consulted
    * in order to generate the package map.  If any of these files is
    * modified, the package map will need to be regenerated.
    */
   Set<String> dependencies;
 
   PackageMapInfo(this.packageMap, this.dependencies);
 }
 
 /**
  * Implementation of PackageMapProvider that operates by executing pub.
  */
 class PubPackageMapProvider implements PackageMapProvider {
   static const String PUB_LIST_COMMAND = 'list-package-dirs';
 
   /**
+   * The name of the 'pubspec.lock' file, which we assume is the dependency
+   * in the event that [PUB_LIST_COMMAND] fails.
+   */
+  static const String PUBSPEC_LOCK_NAME = 'pubspec.lock';
+
+  /**
    * [ResourceProvider] that is used to create the [Folder]s that populate the
    * package map.
    */
   final ResourceProvider resourceProvider;
 
   PubPackageMapProvider(this.resourceProvider);
 
   @override
   PackageMapInfo computePackageMap(Folder folder) {
     // TODO(paulberry) make this asynchronous so that we can (a) do other
     // analysis while it's in progress, and (b) time out if it takes too long
     // to respond.
     String executable = SHARED_SDK.pubExecutable.getAbsolutePath();
     io.ProcessResult result;
     try {
       result = io.Process.runSync(
           executable, [PUB_LIST_COMMAND], workingDirectory: folder.path);
     } on io.ProcessException catch (exception, stackTrace) {
       AnalysisEngine.instance.logger.logInformation(
           "Error running pub $PUB_LIST_COMMAND\n${exception}\n${stackTrace}");
     }
     if (result.exitCode != 0) {
       AnalysisEngine.instance.logger.logInformation(
           "pub $PUB_LIST_COMMAND failed: exit code ${result.exitCode}");
-      return null;
+      return _error(folder);
     }
     try {
       return parsePackageMap(result.stdout);
     } catch (exception, stackTrace) {
       AnalysisEngine.instance.logger.logError(
           "Malformed output from pub $PUB_LIST_COMMAND\n${exception}\n${stackTrace}");
     }
 
-    return null;
+    return _error(folder);
   }
 
   /**
+   * Create a PackageMapInfo object representing an error condition.
+   */
+  PackageMapInfo _error(Folder folder) {
+    // Even if an error occurs, we still need to know the dependencies, so that
+    // we'll know when to try running "pub list-package-dirs" again.
+    // Unfortunately, "pub list-package-dirs" doesn't tell us dependencies when
+    // an error occurs, so just assume there is one dependency, "pubspec.lock".
+    List<String> dependencies = <String>[join(folder.path, PUBSPEC_LOCK_NAME)];
+    return new PackageMapInfo(null, dependencies.toSet());
+  }
+
+  /**
    * Decode the JSON output from pub into a package map.
    */
   PackageMapInfo parsePackageMap(String jsonText) {
     // The output of pub looks like this:
     // {
     //   "packages": {
     //     "foo": "path/to/foo",
     //     "bar": ["path/to/bar1", "path/to/bar2"],
     //     "myapp": "path/to/myapp",  // self link is included
     //   },
@@ skipping 30 matching lines @@
     if (inputFiles != null) {
       for (var path in inputFiles) {
         if (path is String) {
           dependencies.add(path);
         }
       }
     }
     return new PackageMapInfo(packageMap, dependencies);
   }
 }