Support custom fetch function

example/capacitor/src/pages/Home.tsx

@@ -93,6 +93,15 @@ function isPlatformWeb(): boolean {
   return Capacitor.getPlatform() === "web";
 }
 
+async function myfetch(
+  input: URL | RequestInfo,
+  init?: RequestInit
+): Promise<Response> {
+  const request = new Request(input, init);
+  request.headers.set("x-custom-header", "42");
+  return fetch(request);
+}
+
 function AuthgearDemo() {
   const [isAlertOpen, setIsAlertOpen] = useState(false);
   const [alertHeader, setAlertHeader] = useState("");
@@ -228,6 +237,7 @@ function AuthgearDemo() {
           endpoint,
           sessionType: "refresh_token",
           isSSOEnabled,
+          fetch: myfetch,
         });
       } else {
         await authgearCapacitor.configure({
@@ -246,6 +256,7 @@ function AuthgearDemo() {
             : undefined,
           isSSOEnabled,
           preAuthenticatedURLEnabled,
+          fetch: myfetch,
         });
       }
       await postConfigure();

example/reactnative/src/screens/MainScreen.tsx

@@ -145,6 +145,16 @@ const biometricOptions: BiometricOptions = {
   },
 };
 
+async function myfetch(
+  input: URL | RequestInfo,
+  init?: RequestInit,
+): Promise<Response> {
+  // @ts-expect-error The Request class in React Native does not take URL in the first argument.
+  const request = new Request(input, init);
+  request.headers.set('x-custom-header', '42');
+  return fetch(request);
+}
+
 const HomeScreen: React.FC = () => {
   const [initialized, setInitialized] = useState(false);
   const [loading, setLoading] = useState(false);
@@ -383,6 +393,7 @@ const HomeScreen: React.FC = () => {
           : undefined,
         isSSOEnabled,
         preAuthenticatedURLEnabled,
+        fetch: myfetch,
       })
       .then(() => {
         postConfigure();

example/reactweb/src/App.tsx

@@ -83,6 +83,15 @@ function ShowError(props: { error: unknown }) {
   return <pre>{JSON.stringify(data, null, 2)}</pre>;
 }
 
+async function myfetch(
+  input: URL | RequestInfo,
+  init?: RequestInit
+): Promise<Response> {
+  const request = new Request(input, init);
+  request.headers.set("x-custom-header", "42");
+  return fetch(request);
+}
+
 function Root() {
   const initialClientID = readClientID();
   const initialEndpoint = readEndpoint();
@@ -94,7 +103,8 @@ function Root() {
   const [endpoint, setEndpoint] = useState(initialEndpoint);
   const [isSSOEnabled, setIsSSOEnabled] = useState(initialIsSSOEnabled);
   const [page, setPage] = useState<string>();
-  const [authenticationFlowGroup, setAuthenticationflowGroup] = useState<string>("");
+  const [authenticationFlowGroup, setAuthenticationflowGroup] =
+    useState<string>("");
 
   const [error, setError] = useState<unknown>(null);
   const [userInfo, setUserInfo] = useState<UserInfo | null>(null);
@@ -122,6 +132,7 @@ function Root() {
           clientID,
           sessionType,
           isSSOEnabled,
+          fetch: myfetch,
         })
         .then(
           () => {
@@ -225,21 +236,24 @@ function Root() {
       );
   }, []);
 
-  const onClickSignIn = useCallback((e: React.MouseEvent<HTMLElement>) => {
-    e.preventDefault();
-    e.stopPropagation();
-    authgear
-      .startAuthentication({
-        redirectURI: makeRedirectURI(),
-        state: "authenticate",
-        page,
-        authenticationFlowGroup,
-      })
-      .then(
-        () => {},
-        (err) => setError(err)
-      );
-  }, [page, authenticationFlowGroup]);
+  const onClickSignIn = useCallback(
+    (e: React.MouseEvent<HTMLElement>) => {
+      e.preventDefault();
+      e.stopPropagation();
+      authgear
+        .startAuthentication({
+          redirectURI: makeRedirectURI(),
+          state: "authenticate",
+          page,
+          authenticationFlowGroup,
+        })
+        .then(
+          () => {},
+          (err) => setError(err)
+        );
+    },
+    [page, authenticationFlowGroup]
+  );
 
   const onClickSignInAnonymously = useCallback(
     (e: React.MouseEvent<HTMLElement>) => {

packages/authgear-capacitor/src/index.ts

@@ -119,14 +119,16 @@ export interface ConfigureOptions {
    * The UIImplementation.
    */
   uiImplementation?: UIImplementation;
-}
 
-/**
- * @internal
- */
-export class _CapacitorAPIClient extends _BaseAPIClient {
-  _fetchFunction = window.fetch.bind(window);
-  _requestClass = Request;
+  /*
+   * Override the fetch() function the SDK uses to access the endpoint.
+   * If this is not specified, the global fetch() function is used.
+   * Note that the fetch() function IS NOT used in the UIImplementation,
+   * it is only used to access endpoints like the Token endpoint.
+   * For example, you want to provide a custom fetch() function to include additional headers
+   * in all requests that are sent to your self-hosted deployment.
+   */
+  fetch?: typeof window.fetch;
 }
 
 async function getXDeviceInfo(): Promise<string> {
@@ -151,7 +153,7 @@ export class CapacitorContainer {
   /**
    * @internal
    */
-  baseContainer: _BaseContainer<_CapacitorAPIClient>;
+  baseContainer: _BaseContainer<_BaseAPIClient>;
 
   /**
    * @internal
@@ -270,13 +272,14 @@ export class CapacitorContainer {
       },
     });
     this.dpopProvider = dpopProvider;
-    const apiClient = new _CapacitorAPIClient(dpopProvider);
 
-    this.baseContainer = new _BaseContainer<_CapacitorAPIClient>(
-      o,
-      apiClient,
-      this
-    );
+    const apiClient = new _BaseAPIClient({
+      fetch: window.fetch.bind(window),
+      Request: Request,
+      dpopProvider,
+    });
+
+    this.baseContainer = new _BaseContainer<_BaseAPIClient>(o, apiClient, this);
     this.baseContainer.apiClient._delegate = this;
 
     this.storage = new PersistentContainerStorage();
@@ -373,7 +376,11 @@ export class CapacitorContainer {
     const refreshToken = await this.tokenStorage.getRefreshToken(this.name);
 
     this.clientID = options.clientID;
+
+    this.baseContainer.apiClient._fetch =
+      options.fetch ?? window.fetch.bind(window);
     this.baseContainer.apiClient.endpoint = options.endpoint;
+
     this.baseContainer.refreshToken = refreshToken ?? undefined;
     this.baseContainer.accessToken = undefined;
 

packages/authgear-core/src/client.ts

@@ -26,7 +26,7 @@ export function _removeTrailingSlash(s: string): string {
 /**
  * @internal
  */
-export abstract class _BaseAPIClient {
+export class _BaseAPIClient {
   private dpopProvider: DPoPProvider | null;
   userAgent?: string;
 
@@ -47,15 +47,21 @@ export abstract class _BaseAPIClient {
   }
 
   // eslint-disable-next-line no-undef
-  abstract _fetchFunction?: typeof fetch;
-
+  _fetch: typeof fetch;
   // eslint-disable-next-line no-undef
-  abstract _requestClass?: typeof Request;
+  _Request: typeof Request;
 
   _config?: _OIDCConfiguration;
 
-  constructor(dpopProvider: DPoPProvider | null) {
-    this.dpopProvider = dpopProvider;
+  constructor(options: {
+    // eslint-disable-next-line no-undef
+    fetch: typeof fetch;
+    Request: typeof Request;
+    dpopProvider: DPoPProvider | null;
+  }) {
+    this._fetch = options.fetch;
+    this._Request = options.Request;
+    this.dpopProvider = options.dpopProvider;
   }
 
   protected async _prepareHeaders(): Promise<Record<string, string>> {
@@ -71,10 +77,6 @@ export abstract class _BaseAPIClient {
   }
 
   async _doFetch(request: Request): Promise<Response> {
-    if (!this._fetchFunction) {
-      throw new AuthgearError("missing fetchFunction in api client");
-    }
-
     if (this.dpopProvider != null) {
       const dpopJWT = await this.dpopProvider.generateDPoPProof({
         htm: request.method,
@@ -85,25 +87,18 @@ export abstract class _BaseAPIClient {
       }
     }
 
-    return this._fetchFunction(request);
+    return this._fetch(request);
   }
 
   async _fetchWithoutRefresh(
     url: string,
     init?: RequestInit
   ): Promise<Response> {
-    if (!this._requestClass) {
-      throw new AuthgearError("missing requestClass in api client");
-    }
-    const request = new this._requestClass(url, init);
+    const request = new this._Request(url, init);
     return this._doFetch(request);
   }
 
   async fetch(input: RequestInfo | URL, init?: RequestInit): Promise<Response> {
-    if (this._requestClass == null) {
-      throw new AuthgearError("missing requestClass in api client");
-    }
-
     if (this._delegate == null) {
       throw new AuthgearError("missing delegate in api client");
     }
@@ -113,7 +108,7 @@ export abstract class _BaseAPIClient {
       await this._delegate.refreshAccessToken();
     }
 
-    const request = new this._requestClass(input, init);
+    const request = new this._Request(input, init);
 
     const headers = await this._prepareHeaders();
     for (const key of Object.keys(headers)) {

packages/authgear-react-native/src/index.ts

@@ -111,14 +111,16 @@ export interface ConfigureOptions {
    * The implementation of UIImplementation.
    */
   uiImplementation?: UIImplementation;
-}
 
-/**
- * @internal
- */
-export class _ReactNativeAPIClient extends _BaseAPIClient {
-  _fetchFunction = fetch;
-  _requestClass = Request;
+  /*
+   * Override the fetch() function the SDK uses to access the endpoint.
+   * If this is not specified, the global fetch() function is used.
+   * Note that the fetch() function IS NOT used in the UIImplementation,
+   * it is only used to access endpoints like the Token endpoint.
+   * For example, you want to provide a custom fetch() function to include additional headers
+   * in all requests that are sent to your self-hosted deployment.
+   */
+  fetch?: typeof fetch;
 }
 
 async function getXDeviceInfo(): Promise<string> {
@@ -143,7 +145,7 @@ export class ReactNativeContainer {
   /**
    * @internal
    */
-  baseContainer: _BaseContainer<_ReactNativeAPIClient>;
+  baseContainer: _BaseContainer<_BaseAPIClient>;
 
   /**
    * @internal
@@ -280,13 +282,13 @@ export class ReactNativeContainer {
     });
 
     this.dpopProvider = dpopProvider;
-    const apiClient = new _ReactNativeAPIClient(dpopProvider);
+    const apiClient = new _BaseAPIClient({
+      fetch: fetch,
+      Request: Request,
+      dpopProvider: dpopProvider,
+    });
 
-    this.baseContainer = new _BaseContainer<_ReactNativeAPIClient>(
-      o,
-      apiClient,
-      this
-    );
+    this.baseContainer = new _BaseContainer<_BaseAPIClient>(o, apiClient, this);
     this.baseContainer.apiClient._delegate = this;
 
     this.storage = new PersistentContainerStorage();
@@ -395,6 +397,7 @@ export class ReactNativeContainer {
     const refreshToken = await this.tokenStorage.getRefreshToken(this.name);
 
     this.clientID = options.clientID;
+    this.baseContainer.apiClient._fetch = options.fetch ?? fetch;
     this.baseContainer.apiClient.endpoint = options.endpoint;
     this.baseContainer.refreshToken = refreshToken ?? undefined;
     this.baseContainer.accessToken = undefined;