fix #607, add support for package config file

lib/src/analyzer/context.dart

Index: lib/src/analyzer/context.dart
diff --git a/lib/src/analyzer/context.dart b/lib/src/analyzer/context.dart
index d418c4209e1ae28a406c3870c7460c8a44af29b6..52dae3017b8cf78053a1c0ef14b9d587be6eab5c 100644
--- a/lib/src/analyzer/context.dart
+++ b/lib/src/analyzer/context.dart
@@ -3,6 +3,7 @@
 // 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.
 
+import 'dart:io' show Directory, File;
 import 'package:analyzer/file_system/file_system.dart' show ResourceUriResolver;
 import 'package:analyzer/file_system/physical_file_system.dart'
     show PhysicalResourceProvider;
@@ -26,6 +27,10 @@ import 'package:analyzer/src/summary/package_bundle_reader.dart'
         SummaryDataStore;
 import 'package:analyzer/src/summary/summary_sdk.dart' show SummaryBasedDartSdk;
 import 'package:cli_util/cli_util.dart' show getSdkDir;
+import 'package:package_config/discovery.dart' show findPackagesFromFile;
+import 'package:package_config/packages.dart' show Packages;
+import 'package:package_config/packages_file.dart' as pkgfile show parse;
+import 'package:package_config/src/packages_impl.dart';
 import 'package:path/path.dart' as path;
 
 import 'multi_package_resolver.dart' show MultiPackageResolver;
@@ -35,9 +40,14 @@ class AnalyzerOptions {
   /// Custom URI mappings, such as "dart:foo" -> "path/to/foo.dart"
   final Map<String, String> customUrlMappings;
 
-  /// Package root when resolving 'package:' urls the standard way.
+  /// Package root directory when resolving 'package:' urls, mutually exclusive
+  /// with [packageConfig].
   final String packageRoot;
 
+  /// Package spec file, typically called `.packages`, mutually exclusive with
+  /// [packageRoot].
+  final String packageConfig;
+
   /// List of summary file paths.
   final List<String> summaryPaths;
 
@@ -57,7 +67,8 @@ class AnalyzerOptions {
       String dartSdkPath,
       this.dartSdkSummaryPath,
       this.customUrlMappings: const {},
-      this.packageRoot: 'packages/',
+      this.packageRoot,
+      this.packageConfig,
       this.packagePaths: const []})
       : dartSdkPath = dartSdkPath ?? getSdkDir().path;
 
@@ -67,6 +78,7 @@ class AnalyzerOptions {
         dartSdkSummaryPath = args['dart-sdk-summary'],
         customUrlMappings = _parseUrlMappings(args['url-mapping']),
         packageRoot = args['package-root'],
+        packageConfig = args['packages'],
         packagePaths = (args['package-paths'] as String)?.split(',') ?? [];
 
   /// Whether to resolve 'package:' uris using the multi-package resolver.
@@ -79,10 +91,14 @@ class AnalyzerOptions {
       ..addOption('dart-sdk', help: 'Dart SDK Path', defaultsTo: null)
       ..addOption('dart-sdk-summary',
           help: 'Dart SDK Summary Path', defaultsTo: null)
+      ..addOption('packages',
+          help: 'Path to the package resolution configuration file, which '
+              'supplies a mapping of package names to paths.  This option '
+              'cannot be used with --package-root.')

[nweiz, 2016/07/27 23:15:11]

It would be good to explicitly throw an error if both of these are provided.

       ..addOption('package-root',
           abbr: 'p',
-          help: 'Package root to resolve "package:" imports',
-          defaultsTo: 'packages/')
+          help: 'Path to a package root directory (deprecated). This option '
+              'cannot be used with --packages.')
       ..addOption('url-mapping',
           help: '--url-mapping=libraryUri,/path/to/library.dart uses \n'
               'library.dart as the source for an import of of "libraryUri".',
@@ -107,7 +123,9 @@ class AnalyzerOptions {
 /// Creates an [AnalysisContext] with dev_compiler type rules and inference,
 /// using [createSourceFactory] to set up its [SourceFactory].
 AnalysisContext createAnalysisContextWithSources(AnalyzerOptions options,
-    {DartUriResolver sdkResolver, List<UriResolver> fileResolvers}) {
+    {DartUriResolver sdkResolver,
+    List<UriResolver> fileResolvers,
+    Packages packages}) {
   AnalysisEngine.instance.processRequiredPlugins();
 
   sdkResolver ??=
@@ -122,6 +140,7 @@ AnalysisContext createAnalysisContextWithSources(AnalyzerOptions options,
   var srcFactory = _createSourceFactory(options,
       sdkResolver: sdkResolver,
       fileResolvers: fileResolvers,
+      packages: packages,
       summaryData: summaryData);
 
   var context = createAnalysisContext();
@@ -153,6 +172,7 @@ AnalysisContextImpl createAnalysisContext() {
 SourceFactory _createSourceFactory(AnalyzerOptions options,
     {DartUriResolver sdkResolver,
     List<UriResolver> fileResolvers,
+    Packages packages,
     SummaryDataStore summaryData}) {
   var resolvers = <UriResolver>[];
   if (options.customUrlMappings.isNotEmpty) {
@@ -163,18 +183,27 @@ SourceFactory _createSourceFactory(AnalyzerOptions options,
     resolvers.add(new InSummaryPackageUriResolver(summaryData));
   }
 
-  if (fileResolvers == null) fileResolvers = createFileResolvers(options);
-  resolvers.addAll(fileResolvers);
-  return new SourceFactory(resolvers);
-}
-
-List<UriResolver> createFileResolvers(AnalyzerOptions options) {
-  return [
-    new ResourceUriResolver(PhysicalResourceProvider.INSTANCE),
-    options.useMultiPackage
-        ? new MultiPackageResolver(options.packagePaths)
-        : new PackageUriResolver([new JavaFile(options.packageRoot)])
-  ];
+  if (fileResolvers == null) {
+    resolvers.add(new ResourceUriResolver(PhysicalResourceProvider.INSTANCE));
+  } else {
+    resolvers.addAll(fileResolvers);
+  }
+  if (packages == null) {
+    if (options.useMultiPackage) {
+      resolvers.add(new MultiPackageResolver(options.packagePaths));
+    } else if (options.packageConfig != null) {
+      var f = new File(options.packageConfig).absolute;
+      packages = new MapPackages(pkgfile.parse(f.readAsBytesSync(), f.uri));
+    } else if (options.packageRoot != null) {
+      resolvers
+          .add(new PackageUriResolver([new JavaFile(options.packageRoot)]));
+    } else {
+      // TODO(jmesserly): should we use the input file paths or base directory
+      // instead?
+      packages = findPackagesFromFile(Directory.current.uri);

[Jennifer Messerly, 2016/07/27 22:56:16]

is using .packages the right default behavior now?

[nweiz, 2016/07/27 23:15:11]

I believe the default is:

* If a packages/ directory exists next to the entrypoint, use that.
* Otherwise, traverse upwards through the filesystem, starting at the
entrypoint's directory, to find a ".packages" file and use that.

Since DDC doesn't really have an "entrypoint" as such, I'm not sure how to make
this work.

[Brian Wilkerson, 2016/07/29 17:07:40]

Almost. A '.packages' file in the initial directory trumps a 'packages'
directory, but a 'packages' directory in the initial directory is used before
any '.packages' files in parent directories.

+    }
+  }
+  return new SourceFactory(resolvers, packages);
 }
 
 DirectoryBasedDartSdk _createDirectoryBasedDartSdk(String sdkPath) {