Make VM resolvePackageUri fail on package:foo and package:/foo.

runtime/bin/vmservice/loader.dart

Index: runtime/bin/vmservice/loader.dart
diff --git a/runtime/bin/vmservice/loader.dart b/runtime/bin/vmservice/loader.dart
index 977fd28f7826d8c435c5da2846ee057adb6a4924..82fbe5e0e11ca845625b9da5b8b49515a6d473c7 100644
--- a/runtime/bin/vmservice/loader.dart
+++ b/runtime/bin/vmservice/loader.dart
@@ -116,15 +116,16 @@ class IsolateLoaderState extends IsolateEmbedderData {
 
   _setPackageRoot(String packageRoot) {
     packageRoot = _sanitizeWindowsPath(packageRoot);
-    packageRoot = _enforceTrailingSlash(packageRoot);
     if (packageRoot.startsWith('file:') ||
         packageRoot.startsWith('http:') ||
         packageRoot.startsWith('https:')) {
+      packageRoot = _enforceTrailingSlash(packageRoot);
       _packageRoot = _workingDirectory.resolve(packageRoot);
     } else {
       packageRoot = _sanitizeWindowsPath(packageRoot);
       packageRoot = _trimWindowsPath(packageRoot);
-      _packageRoot = _workingDirectory.resolveUri(new Uri.file(packageRoot));
+      _packageRoot =
+          _workingDirectory.resolveUri(new Uri.directory(packageRoot));
     }
   }
 
@@ -163,12 +164,12 @@ class IsolateLoaderState extends IsolateEmbedderData {
   List<Function> _pendingPackageLoads = [];
 
   // Given a uri with a 'package' scheme, return a Uri that is prefixed with
-  // the package root.
+  // the package root or resolved relative to the package configuration.
   Uri _resolvePackageUri(Uri uri) {
     assert(uri.scheme == "package");
     assert(_packagesReady);
 
-    if (!uri.host.isEmpty) {
+    if (uri.host.isNotEmpty) {
       var path = '${uri.host}${uri.path}';
       var right = 'package:$path';
       var wrong = 'package://$path';
@@ -177,6 +178,12 @@ class IsolateLoaderState extends IsolateEmbedderData {
             "'$right', not '$wrong'.";
     }
 
+    var packageNameEnd = uri.path.indexOf('/');
+    if (packageNameEnd == 0) {
+      // Package URIs must have a non-empty package name (not start with "/").
+      throw "URIS using the 'package:' scheme should look like "
+            "'package:packageName${uri.path}', not 'package:${uri.path}'";
+    }
     if (_traceLoading) {
       _log('Resolving package with uri path: ${uri.path}');
     }
@@ -189,7 +196,13 @@ class IsolateLoaderState extends IsolateEmbedderData {
     } else if (_packageRoot != null) {
       resolvedUri = _packageRoot.resolve(uri.path);
     } else {
-      var packageName = uri.pathSegments[0];
+      if (packageNameEnd < 0) {
+        // Package URIs must have a path after the package name, even if it's
+        // just "/".
+        throw "URIS using the 'package:' scheme should look like "
+              "'package:${uri.path}/', not 'package:${uri.path}'";
+      }
+      var packageName = uri.path.substring(0, packageNameEnd);
       var mapping = _packageMap[packageName];
       if (_traceLoading) {
         _log("Mapped '$packageName' package to '$mapping'");
@@ -198,14 +211,8 @@ class IsolateLoaderState extends IsolateEmbedderData {
         throw "No mapping for '$packageName' package when resolving '$uri'.";
       }
       var path;
-      if (uri.path.length > packageName.length) {
-        path = uri.path.substring(packageName.length + 1);
-      } else {
-        // Handle naked package resolution to the default package name:
-        // package:foo is equivalent to package:foo/foo.dart
-        assert(uri.path.length == packageName.length);
-        path = "$packageName.dart";
-      }
+      assert(uri.path.length > packageName.length);
+      path = uri.path.substring(packageName.length + 1);
       if (_traceLoading) {
         _log("Path to be resolved in package: $path");
       }