Pass the instance to onInit callback (#5023)

* pass the instance to onInit callback

* add a test for instance passing

* Create sharp-pans-share.md

Author: Feiyang1

.changeset/sharp-pans-share.md

@@ -0,0 +1,5 @@
+---
+"@firebase/component": patch
+---
+
+Pass the instance to onInit callback

packages/component/src/provider.test.ts

@@ -197,6 +197,20 @@ describe('Provider', () => {
       expect(callback).to.have.been.calledOnce;
     });
 
+    it('passes service instance', () => {
+      const serviceInstance = { test: true };
+      provider.setComponent(getFakeComponent('test', () => serviceInstance));
+      const callback = fake();
+
+      // initialize the service instance
+      provider.getImmediate();
+
+      provider.onInit(callback);
+
+      expect(callback).to.have.been.calledOnce;
+      expect(callback).to.have.been.calledWith(serviceInstance);
+    });
+
     it('passes instance identifier', () => {
       provider.setComponent(
         getFakeComponent(

packages/component/src/provider.ts

@@ -272,7 +272,7 @@ export class Provider<T extends Name> {
     existingCallbacks.add(callback);
     this.onInitCallbacks.set(normalizedIdentifier, existingCallbacks);
 
-    const existingInstance = this.instances.has(normalizedIdentifier);
+    const existingInstance = this.instances.get(normalizedIdentifier);
     if (existingInstance) {
       callback(existingInstance, normalizedIdentifier);
     }