add smart detection 'soft circular links'

jsonform.gadget.js

@@ -71,19 +71,40 @@
     return target;
   }
 
-  function checkCircular(g, path, url) {
+  function checkCircular(urls, path, url) {
     var required_stack,
       idx,
-      prev_field_path = getMaxPathInDict(g.props.schema_required_urls, path);
-    required_stack = g.props.schema_required_urls[prev_field_path] || [];
+      prev_field_path = getMaxPathInDict(urls, path);
+    required_stack = urls[prev_field_path] || [];
     idx = required_stack.indexOf(url);
     if (idx >= 0) {
       if (path === prev_field_path && idx === 0) {
         return;
       }
-      throw new Error("Circular reference detected");
+      return true;
+    }
+    // copy and add url as first element
+    urls[path] = [url].concat(required_stack);
+  }
+
+  function checkHardCircular(g, path, url) {
+    return checkCircular(g.props.schema_required_urls, path, url);
+  }
+
+  function checkAndMarkSoftCircular(g, schema_arr, path, url) {
+    var ret = true;
+    // if schema_arr.length > 1 selection rendered in any case
+    // so we not need checkCircular and have small optimisation
+    if (schema_arr.length === 1) {
+      ret = checkCircular(g.props.schema_urls, path, url);
+      schema_arr[0].circular = ret;
+    }
+    if (ret) {
+      // if schema_arr.length > 1 selection rendered and loop break
+      // if circular found selection rendered and loop break
+      // so we can begin from start
+      g.props.schema_urls[path] = [];
     }
-    g.props.schema_required_urls[path] = [url].concat(required_stack);
   }
 
   function convertToRealWorldSchemaPath(g, path) {
@@ -261,7 +282,9 @@
       }
       queue
         .push(function (json) {
-          checkCircular(g, path, url);
+          if (checkHardCircular(g, path, url)) {
+            throw new Error("Circular reference detected");
+          }
           return resolveLocalReference(json, hash);
         });
     }
@@ -305,12 +328,7 @@
         return expandSchema(g, schema_part, path, $ref);
       })
       .push(function (schema_arr) {
-        // if length array > 1 form rendered on demand already
-        // so not needed circular detection
-        if (schema_arr.length === 1) {
-          // XXX need smart circular detection in this place
-          schema_arr[0].circular = true;
-        }
+        checkAndMarkSoftCircular(g, schema_arr, path, url);
         return schema_arr;
       });
   }
@@ -740,11 +758,19 @@
         "http://json-schema.org/draft-07/schema": "json-schema/schema7.json",
         "http://json-schema.org/schema": "json-schema/schema7.json"
       };
+      // schema_urls[path] = [
+      // stack urls
+      // "url1",
+      // "url2"
+      // ]
+      // used for break soft circular relation of schemas
+      g.props.schema_urls = {};
       // schema_required_urls[path] = [
       // stack required urls, on every unrequired field stack begining from []
       // "url1",
       // "url2"
       // ]
+      // used for break hard circular relation of schemas
       g.props.schema_required_urls = {};
       // schema_resolve_errors[schema_url] = {
       //   schemaPath: local_schema_path,