fix json validation and empty json handling in advanced settings (ela…

…stic#15531) (elastic#15644)

src/core_plugins/kibana/public/management/sections/settings/advanced_row.html

@@ -64,6 +64,7 @@
           ng-keyup="maybeCancel($event, conf)"
           elastic-textarea
           validate-json
+          data-test-subj="unsavedValueJsonTextArea"
         ></textarea>
 
         <p

src/core_plugins/kibana/public/management/sections/settings/advanced_row.js

@@ -44,6 +44,12 @@ uiModules.get('apps/management')
         };
 
         $scope.save = function (conf) {
+          // an empty JSON is valid as per the validateJson directive.
+          // set the value to empty JSON in this case so that its parsing upon retrieving the setting does not fail.
+          if (conf.type === 'json' && conf.unsavedValue === '') {
+            conf.unsavedValue = '{}';
+          }
+
           loading(conf, function () {
             if (conf.unsavedValue === conf.defVal) {
               return config.remove(conf.name);

src/ui/public/directives/__tests__/validate_json.js

@@ -78,6 +78,10 @@ describe('validate-json directive', function () {
         checkValid(input.invalid, 'ng-invalid');
       });
 
+      it('should be invalid if a number', function () {
+        checkValid('0', 'ng-invalid');
+      });
+
       it('should update validity on changes', function () {
         checkValid(input.valid, 'ng-valid');
         checkValid(input.invalid, 'ng-invalid');

src/ui/public/directives/validate_json.js

@@ -21,7 +21,7 @@ module.directive('validateJson', function () {
 
         // We actually need a proper object in all JSON inputs
         newValue = (newValue || '').trim();
-        if (newValue[0] === '{' || '[') {
+        if (newValue[0] === '{' || newValue[0] === '[') {
           try {
             JSON.parse(newValue);
             setValid();

test/functional/apps/management/_kibana_settings.js

@@ -28,6 +28,13 @@ export default function ({ getService, getPageObjects }) {
       expect(advancedSetting).to.be('America/Phoenix');
     });
 
+    it('should coerce an empty setting of type JSON into an empty object', async function () {
+      await PageObjects.settings.clickKibanaSettings();
+      await PageObjects.settings.setAdvancedSettingsInput('query:queryString:options', '', 'unsavedValueJsonTextArea');
+      const advancedSetting = await PageObjects.settings.getAdvancedSettings('query:queryString:options');
+      expect(advancedSetting).to.be.eql('{}');
+    });
+
     describe('state:storeInSessionStorage', () => {
       it ('defaults to false', async () => {
         await PageObjects.settings.clickKibanaSettings();