ReplicateStorage: use stable data hash

JSON.stringify is not stable by design and can not be used to generate the hash.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify

This commit adds a stable version of JSON.stringify, available at jIO.util.stringify.
Relying on the nearly same string representation will simplify compatibility.

src/jio.js

@@ -110,6 +110,38 @@
   }
   util.readBlobAsDataURL = readBlobAsDataURL;
 
+  function stringify(obj) {
+    // Implement a stable JSON.stringify
+    // Object's keys are alphabetically ordered
+    var key,
+      key_list,
+      i,
+      value,
+      result_list;
+    if (obj.constructor === Object) {
+      key_list = Object.keys(obj).sort();
+      result_list = [];
+      for (i = 0; i < key_list.length; i += 1) {
+        key = key_list[i];
+        value = stringify(obj[key]);
+        if (value !== undefined) {
+          result_list.push(stringify(key) + ':' + value);
+        }
+      }
+      return '{' + result_list.join(',') + '}';
+    }
+    if (obj.constructor === Array) {
+      result_list = [];
+      for (i = 0; i < obj.length; i += 1) {
+        result_list.push(stringify(obj[i]));
+      }
+      return '[' + result_list.join(',') + ']';
+    }
+    return JSON.stringify(obj);
+  }
+  util.stringify = stringify;
+
+
   // https://gist.github.com/davoclavo/4424731
   function dataURItoBlob(dataURI) {
     // convert base64 to raw binary data held in a string

src/jio.storage/replicatestorage.js

@@ -19,7 +19,7 @@
 /*jslint nomen: true*/
 /*global jIO, RSVP, Rusha*/
 
-(function (jIO, RSVP, Rusha) {
+(function (jIO, RSVP, Rusha, stringify) {
   "use strict";
 
   var rusha = new Rusha(),
@@ -46,9 +46,9 @@
     this._remote_sub_storage = jIO.createJIO(spec.remote_sub_storage);
 
     this._signature_hash = "_replicate_" + generateHash(
-      JSON.stringify(spec.local_sub_storage) +
-        JSON.stringify(spec.remote_sub_storage) +
-        JSON.stringify(this._query_options)
+      stringify(spec.local_sub_storage) +
+        stringify(spec.remote_sub_storage) +
+        stringify(this._query_options)
     );
     this._signature_sub_storage = jIO.createJIO({
       type: "document",
@@ -213,14 +213,14 @@
           return getMethod(id);
         })
         .push(function (doc) {
-          var local_hash = generateHash(JSON.stringify(doc)),
+          var local_hash = generateHash(stringify(doc)),
             remote_hash;
           if (remote_doc === undefined) {
             return propagateModification(source, destination, doc, local_hash,
                                          id, options);
           }
 
-          remote_hash = generateHash(JSON.stringify(remote_doc));
+          remote_hash = generateHash(stringify(remote_doc));
           if (local_hash === remote_hash) {
             // Same document
             return context._signature_sub_storage.put(id, {
@@ -239,8 +239,8 @@
           }
           // Already exists on destination
           throw new jIO.util.jIOError("Conflict on '" + id + "': " +
-                                      JSON.stringify(doc) + " !== " +
-                                      JSON.stringify(remote_doc),
+                                      stringify(doc) + " !== " +
+                                      stringify(remote_doc),
                                       409);
         });
     }
@@ -283,7 +283,7 @@
           status_hash = result.hash;
           return destination.get(id)
             .push(function (doc) {
-              var remote_hash = generateHash(JSON.stringify(doc));
+              var remote_hash = generateHash(stringify(doc));
               if (remote_hash === status_hash) {
                 return destination.remove(id)
                   .push(function () {
@@ -322,14 +322,14 @@
         })
         .push(function (result_list) {
           var doc = result_list[0],
-            local_hash = generateHash(JSON.stringify(doc)),
+            local_hash = generateHash(stringify(doc)),
             status_hash = result_list[1].hash;
 
           if (local_hash !== status_hash) {
             // Local modifications
             return destination.get(id)
               .push(function (remote_doc) {
-                var remote_hash = generateHash(JSON.stringify(remote_doc));
+                var remote_hash = generateHash(stringify(remote_doc));
                 if (remote_hash !== status_hash) {
                   // Modifications on both sides
                   if (local_hash === remote_hash) {
@@ -346,8 +346,8 @@
                   }
                   if (conflict_force !== true) {
                     throw new jIO.util.jIOError("Conflict on '" + id + "': " +
-                                                JSON.stringify(doc) + " !== " +
-                                                JSON.stringify(remote_doc),
+                                                stringify(doc) + " !== " +
+                                                stringify(remote_doc),
                                                 409);
                   }
                 }
@@ -570,4 +570,4 @@
 
   jIO.addStorage('replicate', ReplicateStorage);
 
-}(jIO, RSVP, Rusha));
+}(jIO, RSVP, Rusha, jIO.util.stringify));

test/jio.storage/replicatestorage.tests.js

@@ -104,7 +104,7 @@
     equal(jio.__storage._check_remote_modification, false);
 
     equal(jio.__storage._signature_hash,
-          "_replicate_623653d45a4e770a2c9f6b71e3144d18ee1b5bec");
+          "_replicate_11881e431308c0ec8c0e6430be98db380e1b92f8");
   });
 
   test("reject unknow conflict resolution", function () {
@@ -2062,7 +2062,7 @@
       .fail(function (error) {
         ok(error instanceof jIO.util.jIOError);
         equal(error.message, "Cannot find document: " +
-                "_replicate_e0cd4a29dc7c74a9de1d7a9cdbfcbaa776863d67");
+                "_replicate_8662994dcefb3a2ceec61e86953efda8ec6520d6");
         equal(error.status_code, 404);
       })
       .then(function () {
@@ -2076,7 +2076,7 @@
       .fail(function (error) {
         ok(error instanceof jIO.util.jIOError);
         equal(error.message, "Cannot find document: " +
-                "_replicate_e0cd4a29dc7c74a9de1d7a9cdbfcbaa776863d67");
+                "_replicate_8662994dcefb3a2ceec61e86953efda8ec6520d6");
         equal(error.status_code, 404);
       })
       .fail(function (error) {

test/jio/util.js

+(function (jIO, QUnit) {
+  "use strict";
+  var test = QUnit.test,
+    equal = QUnit.equal,
+    module = QUnit.module;
+
+  /////////////////////////////////////////////////////////////////
+  // util.stringify
+  /////////////////////////////////////////////////////////////////
+  module("util.stringify");
+  test("is stable", function () {
+    var str = jIO.util.stringify;
+    // https://developer.mozilla.org/search?q=stringify
+    equal(str({}), '{}');
+    equal(str(true), 'true');
+    equal(str('foo'), '"foo"');
+    equal(str([1, 'false', false]), '[1,"false",false]');
+    equal(str({ x: 5 }), '{"x":5}');
+    equal(str(new Date(Date.UTC(2006, 0, 2, 15, 4, 5))),
+          '"2006-01-02T15:04:05.000Z"');
+    equal(str({ x: 5, y: 6, z: 7 }), '{"x":5,"y":6,"z":7}');
+    equal(str({ z: 7, y: 6, x: 5 }), '{"x":5,"y":6,"z":7}');
+    equal(str(Object.create(null, { x: { value: 'x', enumerable: false },
+                                    y: { value: 'y', enumerable: true } })),
+          '{"y":"y"}');
+
+  });
+
+}(jIO, QUnit));
\ No newline at end of file

test/tests.html

@@ -17,6 +17,7 @@
   <!--script src="jio/util.js"></script-->
   <!--script src="jio/fakestorage.js"></script>
   <script src="jio/tests.js"></script-->
+  <script src="jio/util.js"></script>
 
   <script src="queries/key.tests.js"></script>
   <script src="queries/key-schema.tests.js"></script>