use $id in definitions as url for schema downloading

jsonform.gadget.js

@@ -181,22 +181,50 @@
     }
   }
 
+  function map_url(g, download_url) {
+    var mapped_url = download_url,
+      hash = mapped_url.hash,
+      i,
+      schemas = g.props.schemas,
+      next_mapped_url;
+    // simple defence forever loop
+    for (i = 0; i < Object.keys(schemas).length; i += 1) {
+      next_mapped_url = g.props.schemas[mapped_url.origin + mapped_url.pathname + mapped_url.search];
+      if (next_mapped_url === undefined) {
+        break;
+      }
+      mapped_url = next_mapped_url;
+      if (typeof mapped_url !== "string") {
+        mapped_url = resolveLocalReference(mapped_url, hash);
+        break;
+      }
+      mapped_url = new URL(mapped_url, g.__path);
+      if (hash[0] === '#') {
+        hash = hash.slice(1);
+      }
+      if (hash === '/') {
+        hash = '';
+      }
+      hash = mapped_url.hash + hash;
+    }
+    return mapped_url;
+  }
+
   function loadJSONSchema(g, $ref, path) {
     var protocol,
       url,
       download_url,
       hash,
-      mapped_schema,
+      mapped_url,
       queue;
     // XXX need use `id` property
     if (!path) {
       path = "/";
     }
     url = convertUrlToAbsolute(g, path, decodeURI($ref), window.location);
-    download_url = url.origin + url.pathname + url.search;
-    mapped_schema = g.props.schemas[download_url];
-    if (typeof mapped_schema === "string") {
-      url = new URL(mapped_schema, g.__path);
+    mapped_url = map_url(g, url);
+    if (mapped_url instanceof URL) {
+      url = mapped_url;
     }
     protocol = url.protocol;
     if (protocol === "http:" || protocol === "https:") {
@@ -208,12 +236,13 @@
     download_url = url.origin + url.pathname + url.search;
     hash = url.hash;
     url = url.href;
-    if (typeof mapped_schema === "object") {
+    if (!(mapped_url instanceof URL)) {
       queue = RSVP.Queue()
         .push(function () {
-          return mapped_schema;
+          return mapped_url;
         });
-    } else if (download_url.startsWith("urn:jio:")) {
+    } else {
+      if (download_url.startsWith("urn:jio:")) {
         queue = RSVP.Queue()
           .push(function () {
             return g.downloadJSON(download_url);
@@ -224,11 +253,13 @@
             return downloadJSON(download_url);
           });
       }
-    return queue
+      queue
         .push(function (json) {
           checkCircular(g, path, url);
           return resolveLocalReference(json, hash);
-      })
+        });
+    }
+    return queue
       .push(undefined, function (err) {
         // XXX it will be great to have ability convert json_pointers(hash)
         // in line numbers for pointed to line in rich editors.
@@ -389,6 +420,24 @@
     if (schema.$ref) {
       return loadJSONSchema(g, schema.$ref, schema_path);
     }
+    if (schema.definitions) {
+      var key,
+        d,
+        url,
+        mapped_url;
+      for (key in schema.definitions) {
+        if (schema.definitions.hasOwnProperty(key)) {
+          d = schema.definitions[key];
+          url = d.$id || d.id;
+          if (url) {
+            mapped_url = convertUrlToAbsolute(g, schema_path, '#' + schema_path, window.location);
+            // XXX                     /?
+            mapped_url = mapped_url + 'definitions/' + key;
+            g.props.schemas[url] = mapped_url;
+          }
+        }
+      }
+    }
     return RSVP.Queue()
       .push(function () {
         return [{