Support errors in the RFC 7807-compliant format (#564)

Author: AlekseyMartynov

js-test/test.js

@@ -174,6 +174,25 @@
             QUnit.test("json with string prop", testCase("application/json", JSON.stringify({ any: SAMPLE_MESSAGE }), SAMPLE_MESSAGE));
             QUnit.test("other json used verbatim", testCase("application/json", "[{}]", "[{}]"));
             QUnit.test("other mime", testCase("unknown/unknown", "any", "Bad Request"));
+
+            QUnit.test("RFC 7807 - title", testCase(
+                "application/json",
+                JSON.stringify({
+                    type: "https://tools.ietf.org/html/rfc7231#section-6.6.1",
+                    title: SAMPLE_MESSAGE,
+                    detail: "any"
+                }),
+                SAMPLE_MESSAGE
+            ));
+
+            QUnit.test("RFC 7807 - detail fallback", testCase(
+                "application/json",
+                JSON.stringify({
+                    detail: SAMPLE_MESSAGE
+                }),
+                SAMPLE_MESSAGE
+            ))
+
         });
 
         QUnit.test("Issue #146", function(assert) {

js/dx.aspnet.data.js

@@ -367,7 +367,8 @@
 
     function getErrorMessageFromXhr(xhr) {
         var mime = xhr.getResponseHeader("Content-Type"),
-            responseText = xhr.responseText;
+            responseText = xhr.responseText,
+            candidate;
 
         if(!mime)
             return null;
@@ -378,13 +379,22 @@
         if(mime.indexOf("application/json") === 0) {
             var jsonObj = safeParseJSON(responseText);
 
-            if(typeof jsonObj === "string")
+            if(isNonEmptyString(jsonObj))
                 return jsonObj;
 
             if(typeof jsonObj === "object") {
+                candidate = jsonObj.title;
+                if(isNonEmptyString(candidate))
+                    return candidate;
+
+                candidate = jsonObj.detail;
+                if(isNonEmptyString(candidate))
+                    return candidate;
+
                 for(var key in jsonObj) {
-                    if(typeof jsonObj[key] === "string")
-                        return jsonObj[key];
+                    candidate = jsonObj[key];
+                    if(isNonEmptyString(candidate))
+                        return candidate;
                 }
             }
 
@@ -402,6 +412,10 @@
         }
     }
 
+    function isNonEmptyString(value) {
+        return typeof value === "string" && value.length > 0;
+    }
+
     return {
         createStore: function(options) {
             return new CustomStore(createStoreConfig(options));