Merge pull request #8945 from backstage/identity/reliable-methods

[Identity] Wait for implementation instead of throwing

.changeset/varldens-starkaste-bjorn.md

@@ -0,0 +1,7 @@
+---
+'@backstage/core-app-api': patch
+---
+
+Asynchronous methods on the identity API can now reliably be called at any time, including early in the bootstrap process or prior to successful sign-in.
+
+Previously in such situations, a `Tried to access IdentityApi before app was loaded` error would be thrown. Now, those methods will wait and resolve eventually (as soon as a concrete identity API is provided).

packages/core-app-api/src/apis/implementations/IdentityApi/AppIdentityProxy.ts

@@ -47,10 +47,19 @@ type CompatibilityIdentityApi = IdentityApi & {
  */
 export class AppIdentityProxy implements IdentityApi {
   private target?: CompatibilityIdentityApi;
+  private waitForTarget: Promise<CompatibilityIdentityApi>;
+  private resolveTarget: (api: CompatibilityIdentityApi) => void = () => {};
+
+  constructor() {
+    this.waitForTarget = new Promise<CompatibilityIdentityApi>(resolve => {
+      this.resolveTarget = resolve;
+    });
+  }
 
   // This is called by the app manager once the sign-in page provides us with an implementation
   setTarget(identityApi: CompatibilityIdentityApi) {
     this.target = identityApi;
+    this.resolveTarget(identityApi);
   }
 
   getUserId(): string {
@@ -76,17 +85,13 @@ export class AppIdentityProxy implements IdentityApi {
   }
 
   async getProfileInfo(): Promise<ProfileInfo> {
-    if (!this.target) {
-      throw mkError('getProfileInfo');
-    }
-    return this.target.getProfileInfo();
+    return this.waitForTarget.then(target => target.getProfileInfo());
   }
 
   async getBackstageIdentity(): Promise<BackstageUserIdentity> {
-    if (!this.target) {
-      throw mkError('getBackstageIdentity');
-    }
-    const identity = await this.target.getBackstageIdentity();
+    const identity = await this.waitForTarget.then(target =>
+      target.getBackstageIdentity(),
+    );
     if (!identity.userEntityRef.match(/^.*:.*\/.*$/)) {
       // eslint-disable-next-line no-console
       console.warn(
@@ -99,28 +104,21 @@ export class AppIdentityProxy implements IdentityApi {
   }
 
   async getCredentials(): Promise<{ token?: string | undefined }> {
-    if (!this.target) {
-      throw mkError('getCredentials');
-    }
-    return this.target.getCredentials();
+    return this.waitForTarget.then(target => target.getCredentials());
   }
 
   async getIdToken(): Promise<string | undefined> {
-    if (!this.target) {
-      throw mkError('getIdToken');
-    }
-    if (!this.target.getIdToken) {
-      throw new Error('IdentityApi does not implement getIdToken');
-    }
-    logDeprecation('getIdToken');
-    return this.target.getIdToken();
+    return this.waitForTarget.then(target => {
+      if (!target.getIdToken) {
+        throw new Error('IdentityApi does not implement getIdToken');
+      }
+      logDeprecation('getIdToken');
+      return target.getIdToken();
+    });
   }
 
   async signOut(): Promise<void> {
-    if (!this.target) {
-      throw mkError('signOut');
-    }
-    await this.target.signOut();
+    await this.waitForTarget.then(target => target.signOut());
     location.reload();
   }
 }