dart2js: fail gracefully with invalid package config

pkg/compiler/lib/src/apiimpl.dart

Index: pkg/compiler/lib/src/apiimpl.dart
diff --git a/pkg/compiler/lib/src/apiimpl.dart b/pkg/compiler/lib/src/apiimpl.dart
index a2c7d8c9a957ded550c1991ec264f4199629e78d..3352ac1b616d0acdfed746a4b655d43bdc769037 100644
--- a/pkg/compiler/lib/src/apiimpl.dart
+++ b/pkg/compiler/lib/src/apiimpl.dart
@@ -394,13 +394,22 @@ class Compiler extends leg.Compiler {
         }
         // 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) {