[gsi_web] Do not initialize CodeClient if scopes are empty. (flutter#5537)

When initializing a `CodeClient`, it is mandatory to pass at least one `scope` (or the JS initialization will crash).

This PR ensures that the `CodeClient` is not created unless `initialScopes.isNotEmpty`, and lets the user know when attempting to use said client that it hasn't been initialized properly.

## Issues

* Fixes: flutter#139382
* Fixes: flutter#62474
* Closes: flutter/cocoon#3304 (makes this PR unneeded)

## Tests

* Tested locally with `cocoon`.

Author: ditman

packages/google_sign_in/google_sign_in_web/CHANGELOG.md

@@ -1,4 +1,8 @@
-## 0.12.2
+## 0.12.2+1
+
+* Re-publishes `0.12.2` with a small fix to the CodeClient initialization.
+
+## 0.12.2 (withdrawn)
 
 * Adds server auth code retrieval to google_sign_in_web.
 * Adds `web_only` library to access web-only methods more easily.

packages/google_sign_in/google_sign_in_web/lib/src/gis_client.dart

@@ -52,13 +52,15 @@ class GisSdkClient {
       onError: _onTokenError,
     );
 
-    _codeClient = _initializeCodeClient(
-      clientId,
-      hostedDomain: hostedDomain,
-      onResponse: _onCodeResponse,
-      onError: _onCodeError,
-      scopes: initialScopes,
-    );
+    if (initialScopes.isNotEmpty) {
+      _codeClient = _initializeCodeClient(
+        clientId,
+        hostedDomain: hostedDomain,
+        onResponse: _onCodeResponse,
+        onError: _onCodeError,
+        scopes: initialScopes,
+      );
+    }
   }
 
   void _logIfEnabled(String message, [List<Object?>? more]) {
@@ -291,7 +293,13 @@ class GisSdkClient {
   /// Requests a server auth code per:
   /// https://developers.google.com/identity/oauth2/web/guides/use-code-model#initialize_a_code_client
   Future<String?> requestServerAuthCode() async {
-    _codeClient.requestCode();
+    // TODO(dit): Enable granular authorization, https://github.com/flutter/flutter/issues/139406
+    assert(_codeClient != null,
+        'CodeClient not initialized correctly. Ensure the `scopes` list passed to `init()` or `initWithParams()` is not empty!');
+    if (_codeClient == null) {
+      return null;
+    }
+    _codeClient!.requestCode();
     final CodeResponse response = await _codeResponses.stream.first;
     return response.code;
   }
@@ -461,7 +469,8 @@ class GisSdkClient {
 
   // The Google Identity Services client for oauth requests.
   late TokenClient _tokenClient;
-  late CodeClient _codeClient;
+  // CodeClient will not be created if `initialScopes` is empty.
+  CodeClient? _codeClient;
 
   // Streams of credential and token responses.
   late StreamController<CredentialResponse> _credentialResponses;

packages/google_sign_in/google_sign_in_web/pubspec.yaml

@@ -3,7 +3,7 @@ description: Flutter plugin for Google Sign-In, a secure authentication system
   for signing in with a Google account on Android, iOS and Web.
 repository: https://github.com/flutter/packages/tree/main/packages/google_sign_in/google_sign_in_web
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+google_sign_in%22
-version: 0.12.2
+version: 0.12.2+1
 
 environment:
   sdk: ">=3.1.0 <4.0.0"