[ML] guards for uiSettings and fieldRegistry, add custom errors

x-pack/plugins/ml/server/shared_services/errors.ts

@@ -5,9 +5,13 @@
  * 2.0.
  */
 
-export class MLClusterClientUninitialized extends Error {
-  constructor(message?: string) {
-    super(message);
-    Object.setPrototypeOf(this, new.target.prototype);
-  }
-}
+export const getCustomError = (className: string, errorMessage: string) => {
+  const C = class extends Error {
+    constructor(message?: string) {
+      super(message);
+      Object.setPrototypeOf(this, new.target.prototype);
+    }
+  };
+  Object.defineProperty(C, 'name', { value: className });
+  return new C(errorMessage);
+};

x-pack/plugins/ml/server/shared_services/shared_services.ts

@@ -28,7 +28,7 @@ import {
 } from './providers/anomaly_detectors';
 import { ResolveMlCapabilities, MlCapabilitiesKey } from '../../common/types/capabilities';
 import { hasMlCapabilitiesProvider, HasMlCapabilities } from '../lib/capabilities';
-import { MLClusterClientUninitialized } from './errors';
+import { getCustomError } from './errors';
 import { MlClient, getMlClient } from '../lib/ml_client';
 import { jobSavedObjectServiceFactory, JobSavedObjectService } from '../saved_objects';
 import {
@@ -191,14 +191,39 @@ function getRequestItemsProvider(
       isMlReady
     );
 
-    const uiSettingsClient = getUiSettings()!.asScopedToClient(savedObjectsClient);
-    const getFieldsFormatRegistry = () =>
-      getFieldsFormat()!.fieldFormatServiceFactory(uiSettingsClient);
-
     if (clusterClient === null) {
-      throw new MLClusterClientUninitialized(`ML's cluster client has not been initialized`);
+      throw getCustomError(
+        'MLClusterClientUninitialized',
+        `ML's cluster client has not been initialized`
+      );
     }
 
+    const uiSettingsClient = getUiSettings()!.asScopedToClient(savedObjectsClient);
+    if (uiSettingsClient === null) {
+      throw getCustomError(
+        'MLUISettingsClientUninitialized',
+        `ML's UI settings client has not been initialized`
+      );
+    }
+
+    const getFieldsFormatRegistry = async () => {
+      let fieldFormatRegistry;
+      try {
+        fieldFormatRegistry = await getFieldsFormat()!.fieldFormatServiceFactory(uiSettingsClient);
+      } catch (e) {
+        // throw an custom error during the fieldFormatRegistry check
+      }
+
+      if (!fieldFormatRegistry) {
+        throw getCustomError(
+          'MLFieldFormatRegistryUninitialized',
+          `ML's field format registry has not been initialized`
+        );
+      }
+
+      return fieldFormatRegistry;
+    };
+
     if (request instanceof KibanaRequest) {
       hasMlCapabilities = getHasMlCapabilities(request);
       scopedClient = clusterClient.asScoped(request);