Bug 484579 - nsIMIMEService.getTypeFromExtension may fail unexpectedly on Windows when "Content Type" is empty in the registry; Test case; r=sdwilsh

uriloader/exthandler/tests/unit/test_getTypeFromExtension_with_empty_Content_Type.js

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+/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is Mozilla Automated Testing Code.
+ *
+ * The Initial Developer of the Original Code is
+ * Paolo Amadini <http://www.amadzone.org/>.
+ * Portions created by the Initial Developer are Copyright (C) 2009
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+/**
+ * Test for bug 484579 <https://bugzilla.mozilla.org/show_bug.cgi?id=484579>:
+ * nsIMIMEService.getTypeFromExtension may fail unexpectedly on Windows when
+ * "Content Type" is empty in the registry.
+ */
+function run_test() {
+  Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+  // --- Modified nsIWindowsRegKey implementation ---
+
+  /**
+   * Constructs a new mock registry key by wrapping the provided object.
+   *
+   * This mock implementation is tailored for this test, and forces consumers
+   * of the readStringValue method to believe that the "Content Type" value of
+   * the ".txt" key under HKEY_CLASSES_ROOT is an empty string.
+   *
+   * The same value read from "HKEY_LOCAL_MACHINE\SOFTWARE\Classes" is not
+   * affected.
+   *
+   * @param aWrappedObject   An actual nsIWindowsRegKey implementation.
+   */
+  function MockWindowsRegKey(aWrappedObject) {
+    this._wrappedObject = aWrappedObject;
+
+    // This function creates a forwarding function for wrappedObject
+    function makeForwardingFunction(functionName) {
+      return function() {
+        return aWrappedObject[functionName].apply(aWrappedObject, arguments);
+      }
+    }
+
+    // Forward all the functions that are not explicitly overridden
+    for (var propertyName in aWrappedObject) {
+      if (!(propertyName in this)) {
+        if (typeof aWrappedObject[propertyName] == "function") {
+          this[propertyName] = makeForwardingFunction(propertyName);
+        } else {
+          this[propertyName] = aWrappedObject[propertyName];
+        }
+      }
+    }
+  }
+
+  MockWindowsRegKey.prototype = {
+    // --- Overridden nsISupports interface functions ---
+
+    QueryInterface: XPCOMUtils.generateQI([Ci.nsIWindowsRegKey]),
+
+    // --- Overridden nsIWindowsRegKey interface functions ---
+
+    open: function(aRootKey, aRelPath, aMode) {
+      // Remember the provided root key and path
+      this._rootKey = aRootKey;
+      this._relPath = aRelPath;
+
+      // Create the actual registry key
+      return this._wrappedObject.open(aRootKey, aRelPath, aMode);
+    },
+
+    openChild: function(aRelPath, aMode) {
+      // Open the child key and wrap it
+      var innerKey = this._wrappedObject.openChild(aRelPath, aMode);
+      var key = new MockWindowsRegKey(innerKey);
+
+      // Set the properties of the child key and return it
+      key._rootKey = this._rootKey;
+      key._relPath = this._relPath + aRelPath;
+      return key;
+    },
+
+    createChild: function(aRelPath, aMode) {
+      // Create the child key and wrap it
+      var innerKey = this._wrappedObject.createChild(aRelPath, aMode);
+      var key = new MockWindowsRegKey(innerKey);
+
+      // Set the properties of the child key and return it
+      key._rootKey = this._rootKey;
+      key._relPath = this._relPath + aRelPath;
+      return key;
+    },
+
+    get childCount() {
+      return this._wrappedObject.childCount;
+    },
+
+    get valueCount() {
+      return this._wrappedObject.valueCount;
+    },
+
+    readStringValue: function(aName) {
+      // If this is the key under test, return a fake value
+      if (this._rootKey == Ci.nsIWindowsRegKey.ROOT_KEY_CLASSES_ROOT &&
+          this._relPath.toLowerCase() == ".txt" &&
+          aName.toLowerCase() == "content type") {
+        return "";
+      }
+
+      // Return the real value in the registry
+      return this._wrappedObject.readStringValue(aName);
+    }
+  };
+
+  // --- Mock nsIWindowsRegKey factory ---
+
+  var componentRegistrar = Components.manager.
+                           QueryInterface(Ci.nsIComponentRegistrar);
+
+  var originalWindowsRegKeyFactory;
+  var mockWindowsRegKeyFactory;
+
+  const kWindowsRegKeyCID = "{a53bc624-d577-4839-b8ec-bb5040a52ff4}";
+  const kWindowsRegKeyContractID = "@mozilla.org/windows-registry-key;1";
+  const kWindowsRegKeyClassName = "nsWindowsRegKey";
+
+  function registerMockWindowsRegKeyFactory() {
+    mockWindowsRegKeyFactory = {
+      createInstance: function(aOuter, aIid) {
+        if (aOuter != null)
+          throw Cr.NS_ERROR_NO_AGGREGATION;
+
+        var innerKey = originalWindowsRegKeyFactory.createInstance(null, aIid);
+        var key = new MockWindowsRegKey(innerKey);
+
+        return key.QueryInterface(aIid);
+      }
+    };
+
+    // Preserve the original factory
+    originalWindowsRegKeyFactory = Components.manager.getClassObject(
+                                   Cc[kWindowsRegKeyContractID], Ci.nsIFactory);
+
+    // Register the mock factory
+    componentRegistrar.registerFactory(
+      Components.ID(kWindowsRegKeyCID),
+      "Mock Windows Registry Key Implementation",
+      kWindowsRegKeyContractID,
+      mockWindowsRegKeyFactory
+    );
+  }
+
+  function unregisterMockWindowsRegKeyFactory() {
+    // Free references to the mock factory
+    componentRegistrar.unregisterFactory(
+      Components.ID(kWindowsRegKeyCID),
+      mockWindowsRegKeyFactory
+    );
+
+    // Restore the original factory
+    componentRegistrar.registerFactory(
+      Components.ID(kWindowsRegKeyCID),
+      kWindowsRegKeyClassName,
+      kWindowsRegKeyContractID,
+      originalWindowsRegKeyFactory
+    );
+  }
+
+  // --- Test support functions ---
+
+  /**
+   * Returns true if the application is executing on Windows.
+   */
+  function isOnWindows() {
+    return ("@mozilla.org/windows-registry-key;1" in Components.classes);
+  }
+
+  // --- Test procedure ---
+
+  // This test is Windows-specific
+  if(isOnWindows()) {
+    // Activate the override of the ".txt" file association data in the registry
+    registerMockWindowsRegKeyFactory();
+    try {
+      // Try and get the MIME type associated with the extension. If this
+      // operation does not throw an unexpected exception, the test succeeds.
+      var type = Cc["@mozilla.org/mime;1"].
+                 getService(Ci.nsIMIMEService).
+                 getTypeFromExtension(".txt");
+    } catch (e if (e instanceof Ci.nsIException &&
+                   e.result == Cr.NS_ERROR_NOT_AVAILABLE)) {
+      // This is an expected exception, thrown if the type can't be determined
+    } finally {
+      // Ensure we restore the original factory when the test is finished
+      unregisterMockWindowsRegKeyFactory();
+    }
+  }
+}