Ensure that a file: URI does not have an empty path.

sdk/lib/core/uri.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.
 
 part of dart.core;
 
 /**
  * A parsed URI, such as a URL.
  *
  * **See also:**
@@ skipping 353 matching lines @@
         char = uri.codeUnitAt(index);
         if (char == _QUESTION || char == _NUMBER_SIGN) {
           break;
         }
         char = EOI;
       }
       state = NOT_IN_PATH;
     }
 
     assert(state == NOT_IN_PATH);
-    bool ensureLeadingSlash = (host != null || scheme == "file");
-    path = _makePath(uri, pathStart, index, null, ensureLeadingSlash);
+    bool isFile = (scheme == "file");
+    bool ensureLeadingSlash = host != null;
+    path = _makePath(uri, pathStart, index, null, ensureLeadingSlash, isFile);
 
     if (char == _QUESTION) {
       int numberSignIndex = uri.indexOf('#', index + 1);
       if (numberSignIndex < 0) {
         query = _makeQuery(uri, index + 1, uri.length, null);
       } else {
         query = _makeQuery(uri, index + 1, numberSignIndex, null);
         fragment = _makeFragment(uri, numberSignIndex + 1, uri.length);
       }
     } else if (char == _NUMBER_SIGN) {
@@ skipping 101 matching lines @@
     // Special case this constructor for backwards compatibility.
     if (query == "") query = null;
     query = _makeQuery(query, 0, _stringOrNullLength(query), queryParameters);
     fragment = _makeFragment(fragment, 0, _stringOrNullLength(fragment));
     port = _makePort(port, scheme);
     bool isFile = (scheme == "file");
     if (host == null &&
         (userInfo.isNotEmpty || port != null || isFile)) {
       host = "";
     }
-    bool ensureLeadingSlash = (host != null || isFile);
+    bool ensureLeadingSlash = host != null;
     path = _makePath(path, 0, _stringOrNullLength(path), pathSegments,
-                     ensureLeadingSlash);
-
+                     ensureLeadingSlash, isFile);
     return new Uri._internal(scheme, userInfo, host, port,
                              path, query, fragment);
   }
 
   /**
    * Creates a new `http` URI from authority, path and query.
    *
    * Examples:
    *
    * ```
@@ skipping 500 matching lines @@
     return scheme;
   }
 
   static String _makeUserInfo(String userInfo, int start, int end) {
     if (userInfo == null) return "";
     return _normalize(userInfo, start, end, _userinfoTable);
   }
 
   static String _makePath(String path, int start, int end,
                           Iterable<String> pathSegments,
-                          bool ensureLeadingSlash) {
-    if (path == null && pathSegments == null) return "";
+                          bool ensureLeadingSlash,
+                          bool isFile) {
+    if (path == null && pathSegments == null) return isFile ? "/" : "";
     if (path != null && pathSegments != null) {
       throw new ArgumentError('Both path and pathSegments specified');
     }
     var result;
     if (path != null) {
       result = _normalize(path, start, end, _pathCharOrSlashTable);
     } else {
       result = pathSegments.map((s) => _uriEncode(_pathCharTable, s)).join("/");
     }
-    if (ensureLeadingSlash && result.isNotEmpty && !result.startsWith("/")) {
+    if (result.isEmpty) {
+      if (isFile) return "/";
+    } else if ((isFile || ensureLeadingSlash) &&
+               result.codeUnitAt(0) != _SLASH) {
       return "/$result";
     }
     return result;
   }
 
   static String _makeQuery(String query, int start, int end,
                            Map<String, String> queryParameters) {
     if (query == null && queryParameters == null) return null;
     if (query != null && queryParameters != null) {
       throw new ArgumentError('Both query and queryParameters specified');
@@ skipping 1211 matching lines @@
       0xafff,   // 0x30 - 0x3f  1111111111110101
                 //              @ABCDEFGHIJKLMNO
       0xffff,   // 0x40 - 0x4f  1111111111111111
                 //              PQRSTUVWXYZ    _
       0x87ff,   // 0x50 - 0x5f  1111111111100001
                 //               abcdefghijklmno
       0xfffe,   // 0x60 - 0x6f  0111111111111111
                 //              pqrstuvwxyz   ~
       0x47ff];  // 0x70 - 0x7f  1111111111100010
 }