Reduce number of created Queue.

Reuse Queue created from callback directly.

src/jio.js

@@ -209,24 +209,42 @@
     }
   }
 
+  function ensurePushableQueue(callback, argument_list, context) {
+    var result;
+    try {
+      result = callback.apply(context, argument_list);
+    } catch (e) {
+      return new RSVP.Queue()
+        .push(function returnPushableError() {
+          return RSVP.reject(e);
+        });
+    }
+    if (result instanceof RSVP.Queue) {
+      return result;
+    }
+    return new RSVP.Queue()
+      .push(function returnPushableResult() {
+        return result;
+      });
+  }
+
   function declareMethod(klass, name, precondition_function, post_function) {
     klass.prototype[name] = function () {
       var argument_list = arguments,
         context = this,
-        precondition_result;
+        precondition_result,
+        storage_method,
+        queue;
 
-      return new RSVP.Queue()
-        .push(function () {
+      // Precondition function are not asynchronous
       if (precondition_function !== undefined) {
-            return precondition_function.apply(
+        precondition_result = precondition_function.apply(
           context.__storage,
           [argument_list, context, name]
         );
       }
-        })
-        .push(function (result) {
-          var storage_method = context.__storage[name];
-          precondition_result = result;
+
+      storage_method = context.__storage[name];
       if (storage_method === undefined) {
         throw new jIO.util.jIOError(
           "Capacity '" + name + "' is not implemented on '" +
@@ -234,22 +252,21 @@
           501
         );
       }
-          return storage_method.apply(
-            context.__storage,
-            argument_list
-          );
-        })
-        .push(function (result) {
+      queue = ensurePushableQueue(storage_method, argument_list,
+                                  context.__storage);
+
       if (post_function !== undefined) {
+        queue
+          .push(function (result) {
             return post_function.call(
               context,
               argument_list,
               result,
               precondition_result
             );
-          }
-          return result;
           });
+      }
+      return queue;
     };
     // Allow chain
     return this;
@@ -281,8 +298,7 @@
   JioProxyStorage.prototype.post = function () {
     var context = this,
       argument_list = arguments;
-    return new RSVP.Queue()
-      .push(function () {
+    return ensurePushableQueue(function () {
       var storage_method = context.__storage.post;
       if (storage_method === undefined) {
         throw new jIO.util.jIOError(
@@ -409,13 +425,8 @@
         501
       );
     }
-    return new RSVP.Queue()
-      .push(function () {
-        return storage_method.apply(
-          context.__storage,
-          argument_list
-        );
-      });
+    return ensurePushableQueue(storage_method, argument_list,
+                               context.__storage);
   };
 
   JioProxyStorage.prototype.hasCapacity = function (name) {
@@ -439,8 +450,7 @@
     if (options === undefined) {
       options = {};
     }
-    return new RSVP.Queue()
-      .push(function () {
+    return ensurePushableQueue(function () {
       if (context.hasCapacity("list") &&
           ((options.query === undefined) || context.hasCapacity("query")) &&
           ((options.sort_on === undefined) || context.hasCapacity("sort")) &&
@@ -449,9 +459,7 @@
           ((options.include_docs === undefined) ||
            context.hasCapacity("include")) &&
           ((options.limit === undefined) || context.hasCapacity("limit"))) {
-          return context.buildQuery(options);
-        }
-      })
+        return context.buildQuery(options)
           .push(function (result) {
             return {
               data: {
@@ -460,6 +468,8 @@
               }
             };
           });
+      }
+    });
   };
 
   declareMethod(JioProxyStorage, "allAttachments", checkId);
@@ -468,8 +478,7 @@
   JioProxyStorage.prototype.repair = function () {
     var context = this,
       argument_list = arguments;
-    return new RSVP.Queue()
-      .push(function () {
+    return ensurePushableQueue(function () {
       var storage_method = context.__storage.repair;
       if (storage_method !== undefined) {
         return context.__storage.repair.apply(context.__storage,