create api-error error subclass. checks status for error handling when reading compliance info

wherehows-web/app/constants/errors/errors.ts

@@ -1,14 +1,14 @@
-import { ApiStatusNumber } from 'wherehows-web/utils/api/shared';
+import { ApiResponseStatus } from 'wherehows-web/utils/api/shared';
 
 /**
  * Returns a default msg for a given status
- * @param {ApiStatusNumber} status
+ * @param {ApiResponseStatus} status
  * @returns {string}
  */
-const apiErrorStatusMessage = (status: ApiStatusNumber): string =>
+const apiErrorStatusMessage = (status: ApiResponseStatus): string =>
   (<{ [prop: number]: string }>{
-    [ApiStatusNumber.NotFound]: 'Could not find the requested resource',
-    [ApiStatusNumber.InternalServerError]: 'An error occurred with the server'
+    [ApiResponseStatus.NotFound]: 'Could not find the requested resource',
+    [ApiResponseStatus.InternalServerError]: 'An error occurred with the server'
   })[status];
 
 export { apiErrorStatusMessage };

wherehows-web/app/utils/api/datasets/compliance.ts

@@ -1,4 +1,6 @@
 import { assert } from '@ember/debug';
+import { ApiResponseStatus } from 'wherehows-web/utils/api';
+import { ApiError } from 'wherehows-web/utils/api/errors/errors';
 import { createInitialComplianceInfo } from 'wherehows-web/utils/datasets/compliance-policy';
 import { datasetUrlById, datasetUrlByUrn } from 'wherehows-web/utils/api/datasets/shared';
 import { ApiStatus } from 'wherehows-web/utils/api/shared';
@@ -82,18 +84,24 @@ const readDatasetCompliance = async (id: number): Promise<IReadComplianceResult>
 };
 
 /**
- * Reads the dataset compliance policy by urn
- * @param {string} urn
+ * Reads the dataset compliance policy by urn.
+ * Resolves with a new compliance policy instance if remote response is ApiResponseStatus.NotFound
+ * @param {string} urn the urn for the related dataset
  * @return {Promise<IReadComplianceResult>}
  */
 const readDatasetComplianceByUrn = async (urn: string): Promise<IReadComplianceResult> => {
-  let { complianceInfo } = await getJSON<Pick<IComplianceGetResponse, 'complianceInfo'>>({
-    url: datasetComplianceUrlByUrn(urn)
-  });
-  const isNewComplianceInfo = !complianceInfo;
+  let complianceInfo: IComplianceGetResponse['complianceInfo'];
+  let isNewComplianceInfo = false;
 
-  if (isNewComplianceInfo) {
+  try {
+    ({ complianceInfo } = await getJSON<Pick<IComplianceGetResponse, 'complianceInfo'>>({
+      url: datasetComplianceUrlByUrn(urn)
+    }));
+  } catch (e) {
+    if (e instanceof ApiError && e.status === ApiResponseStatus.NotFound) {
       complianceInfo = createInitialComplianceInfo(urn);
+      isNewComplianceInfo = true;
+    }
   }
 
   return { isNewComplianceInfo, complianceInfo: complianceInfo! };

wherehows-web/app/utils/api/errors/errors.ts

@@ -1,4 +1,27 @@
 import { apiErrorStatusMessage } from 'wherehows-web/constants/errors/errors';
+import { ApiResponseStatus } from 'wherehows-web/utils/api';
+
+/**
+ * Extends the built-in Error class with attributes related to treating non 200 OK responses
+ * at the api layer as exceptions
+ * @class ApiError
+ * @extends {Error}
+ */
+class ApiError extends Error {
+  /**
+   * Timestamp of when the exception occurred
+   * @readonly
+   * @memberof ApiError
+   */
+  readonly timestamp = new Date();
+
+  constructor(readonly status: ApiResponseStatus, message: string, ...args: Array<any>) {
+    super(...[message, ...args]);
+    // Fixes downlevel compiler limitation with correct prototype chain adjustment
+    // i.e. ensuring this is also `instanceof` subclass
+    Object.setPrototypeOf(this, ApiError.prototype);
+  }
+}
 
 /**
  * Wraps a Response object, pass through json response if no api error,
@@ -12,10 +35,10 @@ const throwIfApiError = async <T>(response: Response): Promise<T> => {
 
   if (!ok) {
     const { msg = apiErrorStatusMessage(status) } = await response.json();
-    throw new Error(msg);
+    throw new ApiError(status, msg);
   }
 
   return response.json();
 };
 
-export { throwIfApiError };
+export { throwIfApiError, ApiError };

wherehows-web/app/utils/api/shared.ts

@@ -26,7 +26,7 @@ export enum ApiStatus {
  * Enumerates the currently available Api statuses
  * @type {number}
  */
-export enum ApiStatusNumber {
+export enum ApiResponseStatus {
   NotFound = 404,
   UnAuthorized = 401,
   InternalServerError = 500