Fix some unnecessary error reports for invalid jar: URLs. Also complete the JAR file portion of the URL.

common/modules/completion.jsm

@@ -340,7 +340,7 @@ var CompletionContext = Class("CompletionContext", {
     get itemPrototype() {
         let res = {};
         function result(quote) {
-            yield ["result", quote ? function () quote[0] + quote[1](this.text) + quote[2]
+            yield ["result", quote ? function () quote[0] + util.trapErrors(1, quote, this.text) + quote[2]
                                    : function () this.text];
         };
         for (let i in iter(this.keys, result(this.quote))) {
@@ -903,6 +903,13 @@ var Completion = Module("completion", {
     // depending on the 'complete' option
     // if the 'complete' argument is passed like "h", it temporarily overrides the complete option
     url: function url(context, complete) {
+        if (/^jar:[^!]*$/.test(context.filter)) {
+            context.advance(4);
+
+            context.quote = context.quote || ["", util.identity, ""];
+            let quote = context.quote[1];
+            context.quote[1] = function (str) quote(str.replace(/!/g, escape));
+        }
 
         if (this.options["urlseparator"])
             var skip = util.regexp("^.*" + this.options["urlseparator"] + "\\s*")

common/modules/io.jsm

@@ -354,7 +354,7 @@ var IO = Module("io", {
      */
     listJar: function listJar(file, path) {
         file = util.getFile(file);
-        if (file) {
+        if (file && file.exists() && file.isFile() && file.isReadable()) {
             // let jar = services.zipReader.getZip(file); Crashes.
             let jar = services.ZipReader(file);
             try {
@@ -366,7 +366,8 @@ var IO = Module("io", {
                         yield entry;
             }
             finally {
-                jar.close();
+                if (jar)
+                    jar.close();
             }
         }
     },
@@ -878,6 +879,9 @@ unlet s:cpo_save
         };
 
         completion.file = function file(context, full, dir) {
+            if (/^jar:[^!]*$/.test(context.filter))
+                context.advance(4);
+
             // dir == "" is expanded inside readDirectory to the current dir
             function getDir(str) str.match(/^(?:.*[\/\\])?/)[0];
             dir = getDir(dir || context.filter);

common/modules/util.jsm

@@ -1722,7 +1722,7 @@ var Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
      */
     trapErrors: function trapErrors(func, self) {
         try {
-            if (isString(func))
+            if (!callable(func))
                 func = self[func];
             return func.apply(self || this, Array.slice(arguments, 2));
         }