Feat: Added Error Logging Apollo Link (#1832)

* Feat: Added Error Logging Apollo Link

* Update errorLoggingLink.test.ts

* Update errorLoggingLink.test.ts

* Update errorLoggingLink.test.ts

.changeset/soft-swans-chew.md

@@ -0,0 +1,5 @@
+---
+'@faustwp/core': patch
+---
+
+Implemented ErrorLoggingLink class to capture GraphQL errors and server errors, providing enhanced error handling and logging capabilities.

packages/faustwp-core/package.json

@@ -41,7 +41,8 @@
     "isomorphic-fetch": "^3.0.0",
     "js-cookie": "^3.0.5",
     "js-sha256": "^0.9.0",
-    "lodash": "^4.17.21"
+    "lodash": "^4.17.21",
+    "zen-observable-ts": "^1.1.0"
   },
   "scripts": {
     "dev": "concurrently \"npm:watch-*\" --prefix-colors \"auto\"",

packages/faustwp-core/src/apollo/errorLoggingLink.ts

@@ -0,0 +1,73 @@
+import {
+  ApolloLink,
+  FetchResult,
+  NextLink,
+  Operation,
+  ServerError,
+} from '@apollo/client';
+import { Observable } from 'zen-observable-ts';
+import { errorLog } from '../utils/log.js';
+
+/**
+ * Checks if the given error is a server error.
+ * @param error The error to check.
+ * @returns A boolean indicating whether the error is a server error.
+ */
+function isServerError(error: unknown): error is ServerError {
+  if (
+    typeof error === 'object' &&
+    error !== null &&
+    'response' in error &&
+    'result' in error &&
+    'statusCode' in error
+  ) {
+    return true;
+  }
+  return false;
+}
+
+/**
+ * Apollo Link that captures GraphQL errors and server errors, and prints them into the console.
+ */
+export class ErrorLoggingLink extends ApolloLink {
+  /**
+   * Intercepts each GraphQL operation request.
+   * @param operation The GraphQL operation being executed.
+   * @param forward The next link in the chain to delegate the operation to.
+   * @returns An Observable with the operation result or error.
+   */
+  // eslint-disable-next-line class-methods-use-this
+  request(
+    operation: Operation,
+    forward: NextLink,
+  ): Observable<FetchResult> | null {
+    return new Observable<FetchResult>((observer) => {
+      const subscription = forward(operation).subscribe({
+        next: (result) => {
+          // Check if there are GraphQL errors in the result
+          if (result.errors && result.errors.length > 0) {
+            errorLog('GraphQL errors:', result.errors);
+          }
+          observer.next(result);
+        },
+        error: (error) => {
+          // Check if the error is a server error
+          if (isServerError(error)) {
+            errorLog('Server error:', error);
+            errorLog('Fetch result:', error.result);
+          } else {
+            errorLog('Network error:', error);
+          }
+          observer.error(error);
+        },
+        complete: () => {
+          observer.complete();
+        },
+      });
+
+      return () => {
+        subscription.unsubscribe();
+      };
+    });
+  }
+}

packages/faustwp-core/src/apollo/index.ts

@@ -0,0 +1 @@
+export * from './errorLoggingLink.js';

packages/faustwp-core/src/client.ts

@@ -1,6 +1,7 @@
 import {
   ApolloClient,
   ApolloClientOptions,
+  ApolloLink,
   createHttpLink,
   InMemoryCache,
   InMemoryCacheConfig,
@@ -16,6 +17,7 @@ import { createPersistedQueryLink } from '@apollo/client/link/persisted-queries'
 import { sha256 } from 'js-sha256';
 // eslint-disable-next-line import/extensions
 import { AppProps } from 'next/app';
+import { ErrorLoggingLink } from './apollo/errorLoggingLink.js';
 import { getAccessToken } from './auth/index.js';
 import { getConfig } from './config/index.js';
 import { getGraphqlEndpoint } from './lib/getGraphqlEndpoint.js';
@@ -56,15 +58,18 @@ export function createApolloClient(authenticated = false) {
     {},
   ) as InMemoryCacheConfig;
 
-  let linkChain = createHttpLink({
-    uri: getGraphqlEndpoint(),
-    /**
-     * Only add this option if usePersistedQueries is not set/false.
-     * When persisted queries is enabled and this flag and useGETForHashedQueries
-     * are both set, there is a conflict and persisted queries does not work.
-     */
-    useGETForQueries: useGETForQueries && !usePersistedQueries,
-  });
+  let linkChain = ApolloLink.from([
+    new ErrorLoggingLink(),
+    createHttpLink({
+      uri: getGraphqlEndpoint(),
+      /**
+       * Only add this option if usePersistedQueries is not set/false.
+       * When persisted queries is enabled and this flag and useGETForHashedQueries
+       * are both set, there is a conflict and persisted queries does not work.
+       */
+      useGETForQueries: useGETForQueries && !usePersistedQueries,
+    }),
+  ]);
 
   // If the user requested to use persisted queries, apply the link.
   if (usePersistedQueries) {