Bug 714994: Restore (limited) url.toFilename and .fromFilename.

They only work for addon-provided resource: URLs when the XPI is unpacked.
Update the tests to exercise this (but only for whatever value of unpack= the
SDK uses: to exercise both sides, you must manually edit
python-lib/cuddlefish/rdf.py and
python-lib/cuddlefish/app-extension/install.rdf, then re-run 'cfx testall').

This reverts 45859d6.

packages/api-utils/lib/url.js

@@ -59,6 +59,43 @@ function newURI(uriStr, base) {
   }
 }
 
+function resolveResourceURI(uri) {
+  var resolved;
+  try {
+    resolved = resProt.resolveURI(uri);
+  } catch (e if e.result == Cr.NS_ERROR_NOT_AVAILABLE) {
+    throw new Error("resource does not exist: " + uri.spec);
+  };
+  return resolved;
+}
+
+let fromFilename = exports.fromFilename = function fromFilename(path) {
+  var file = Cc['@mozilla.org/file/local;1']
+             .createInstance(Ci.nsILocalFile);
+  file.initWithPath(path);
+  return ios.newFileURI(file).spec;
+};
+
+let toFilename = exports.toFilename = function toFilename(url) {
+  var uri = newURI(url);
+  if (uri.scheme == "resource")
+    uri = newURI(resolveResourceURI(uri));
+  if (uri.scheme == "chrome") {
+    var channel = ios.newChannelFromURI(uri);
+    try {
+      channel = channel.QueryInterface(Ci.nsIFileChannel);
+      return channel.file.path;
+    } catch (e if e.result == Cr.NS_NOINTERFACE) {
+      throw new Error("chrome url isn't on filesystem: " + url);
+    }
+  }
+  if (uri.scheme == "file") {
+    var file = uri.QueryInterface(Ci.nsIFileURL).file;
+    return file.path;
+  }
+  throw new Error("cannot map to filename: " + url);
+};
+
 function URL(url, base) {
   if (!(this instanceof URL)) {
      return new URL(url, base);

packages/api-utils/tests/test-url.js

@@ -74,6 +74,62 @@ exports.testParseFTPWithUserPass = function(test) {
   test.assertEqual(info.userPass, "user:pass");
 };
 
+// rootURI is jar:file://...!/ if we're packed, and file://.../ if we're
+// unpacked. url.toFilename() is not required to work for the contents of
+// packed XPIs
+var unpacked = (require("@packaging").rootURI.indexOf("file:") == 0);
+
+exports.testToFilename = function(test) {
+  test.assertRaises(
+    function() { url.toFilename("resource://nonexistent"); },
+    "resource does not exist: resource://nonexistent/",
+    "url.toFilename() on nonexistent resources should throw"
+  );
+
+  if (unpacked)
+    test.assertMatches(url.toFilename(module.uri),
+                       /.*test-url\.js$/,
+                       "url.toFilename() on resource: URIs should work");
+  else
+    test.assertRaises(
+      function() { url.toFilename(module.uri); },
+      "cannot map to filename: "+module.uri,
+      "url.toFilename() can fail for packed XPIs");
+
+  test.assertRaises(
+    function() { url.toFilename("http://foo.com/"); },
+    "cannot map to filename: http://foo.com/",
+    "url.toFilename() on http: URIs should raise error"
+  );
+
+  try {
+    test.assertMatches(
+      url.toFilename("chrome://global/content/console.xul"),
+      /.*console\.xul$/,
+      "url.toFilename() w/ console.xul works when it maps to filesystem"
+    );
+  } catch (e) {
+    if (/chrome url isn\'t on filesystem/.test(e.message))
+      test.pass("accessing console.xul in jar raises exception");
+    else
+      test.fail("accessing console.xul raises " + e);
+  }
+
+  // TODO: Are there any chrome URLs that we're certain exist on the
+  // filesystem?
+  // test.assertMatches(url.toFilename("chrome://myapp/content/main.js"),
+  //                    /.*main\.js$/);
+};
+
+exports.testFromFilename = function(test) {
+  var profileDirName = require("system").pathFor("ProfD");
+  var fileUrl = url.fromFilename(profileDirName);
+  test.assertEqual(url.URL(fileUrl).scheme, 'file',
+                   'url.toFilename() should return a file: url');
+  test.assertEqual(url.fromFilename(url.toFilename(fileUrl)),
+                   fileUrl);
+};
+
 exports.testURL = function(test) {
   let URL = url.URL;
   test.assert(URL("h:foo") instanceof URL, "instance is of correct type");