Translate package URIs to resource URIs for diagnostics.

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 '../compiler.dart' as api;
@@ skipping 405 matching lines @@
     if (identical(kind, api.Diagnostic.ERROR)
         || identical(kind, api.Diagnostic.CRASH)
         || (fatalWarnings && identical(kind, api.Diagnostic.WARNING))) {
       compilationFailed = true;
     }
     // [:span.uri:] might be [:null:] in case of a [Script] with no [uri]. For
     // instance in the [Types] constructor in typechecker.dart.
     if (span == null || span.uri == null) {
       callUserHandler(null, null, null, '$message', kind);
     } else {
-      callUserHandler(span.uri, span.begin, span.end, '$message', kind);
+      // Translate uri into a resource uri if possible.
+      Uri uri = translateUri(null, span.uri);

[ahe, 2015/06/26 07:56:05]

If I understand this correctly, this may invoke a user-provided plugin for
resolving packages.

This code assumes that plugin is idempotent. However, it might be
extraordinarily complicated to implement a plugin such that it is idempotent,
for example, let's say you provide a plugin which reads an external resource
(for example searches directories, or reads a file). 

Also, what happens if the user-provided plugin throws an exception?

There is one source of truth, and that was established when calling the input
provider. If that URI is preserved and used here, no assumptions about
idempotency are needed.

[Johnni Winther, 2015/06/26 10:15:06]

Good point. Will cache the resource URIs.

[Johnni Winther, 2015/06/26 17:06:54]

No need for extra caching; it was already in Script.resourceUri.

+      if (uri == null) {
+        // Use readable uri as fallback.
+        uri = span.uri;
+      }
+      callUserHandler(uri, span.begin, span.end, '$message', kind);
     }
   }
 
   bool get isMockCompilation {
     return mockableLibraryUsed
       && (options.indexOf('--allow-mock-compilation') != -1);
   }
 
   void callUserHandler(Uri uri, int begin, int end,
                        String message, api.Diagnostic kind) {
@@ skipping 32 matching lines @@
     print('$message: ${tryToString(exception)}');
     print(tryToString(stackTrace));
   }
 
   fromEnvironment(String name) => environment[name];
 
   LibraryInfo lookupLibraryInfo(String libraryName) {
     return library_info.LIBRARIES[libraryName];
   }
 }