dart2js: fail gracefully with invalid package config

pkg/compiler/lib/src/apiimpl.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.
 
 library leg_apiimpl;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:package_config/packages.dart';
@@ skipping 376 matching lines @@
       // Use "non-file" packages because the file version requires a [Directory]
       // and we can't depend on 'dart:io' classes.
       packages = new NonFilePackagesDirectoryPackages(packageRoot);
     } else if (packageConfig != null) {
       return callUserProvider(packageConfig).then((packageConfigContents) {
         if (packageConfigContents is String) {
           packageConfigContents = UTF8.encode(packageConfigContents);
         }
         // The input provider may put a trailing 0 byte when it reads a source
         // file, which confuses the package config parser.
-        if (packageConfigContents.length > 0
-            && packageConfigContents.last == 0) {
+        if (packageConfigContents.length > 0 &&
+            packageConfigContents.last == 0) {
           packageConfigContents = packageConfigContents.sublist(
               0, packageConfigContents.length - 1);
         }
-        packages =
-            new MapPackages(pkgs.parse(packageConfigContents, packageConfig));
+        try {
+          packages =
+              new MapPackages(pkgs.parse(packageConfigContents, packageConfig));
+        } on FormatException catch (e) {

[Siggi Cherem (dart-lang), 2015/08/19 22:39:39]

since the error messages are the same, do we actually need both this catch and
the async catchError or would catchError below be enough?

[Harry Terkelsen, 2015/08/19 22:56:30]

Done.

+          reportError(NO_LOCATION_SPANNABLE, MessageKind.INVALID_PACKAGE_CONFIG,

[Siggi Cherem (dart-lang), 2015/08/19 22:39:39]

not a big priority, but it would be interesting to add span locations to the
package files. Maybe open a bug on the package-config package?

[Harry Terkelsen, 2015/08/19 22:56:30]

Filed a FR with package_config:
https://github.com/dart-lang/package_config/issues/33

+              {'uri': packageConfig, 'exception': e});
+          packages = Packages.noPackages;
+        }
+      }).catchError((error) {
+        reportError(NO_LOCATION_SPANNABLE, MessageKind.INVALID_PACKAGE_CONFIG,
+            {'uri': packageConfig, 'exception': error});

[Siggi Cherem (dart-lang), 2015/08/19 22:39:39]

also add `packages = Packages.noPackages`?

[Harry Terkelsen, 2015/08/19 22:56:30]

Done.

       });
     } else {
       if (packagesDiscoveryProvider == null) {
         packages = Packages.noPackages;
       } else {
         return callUserPackagesDiscovery(uri).then((p) {
           packages = p;
         });
       }
     }
@@ skipping 84 matching lines @@
     print('$message: ${tryToString(exception)}');
     print(tryToString(stackTrace));
   }
 
   fromEnvironment(String name) => environment[name];
 
   LibraryInfo lookupLibraryInfo(String libraryName) {
     return library_info.LIBRARIES[libraryName];
   }
 }