[google_sign_in] Update Pigeon for non-nullable generics (#7785)

Updates the Pigeon definition to uses non-nullable generics now that it's possible.

In practice for this plugin it's currently a no-op: the only affected collection is passed from Dart to native, on the Dart side the source was already a `List<String>`, and on the native side we are using languages without nullability support in generics (Java and Obj-C). However, to do this now eliminates tech debt, and will avoid problems if/when the native side switches to Kotlin/Swift.

The Android implementation required some non-trivial changes to adapt to an earlier Pigeon change that we hadn't picked up yet, which was the change from `Result<Void>` (which turned out to be incompatible with Kotlin) to the separate `VoidResult` class.

Part of flutter/flutter#155891

packages/google_sign_in/google_sign_in_android/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 6.1.33
+
+* Updates Pigeon for non-nullable collection type support.
+
 ## 6.1.32
 
 * Updates Java compatibility version to 11.

packages/google_sign_in/google_sign_in_android/android/src/main/java/io/flutter/plugins/googlesignin/GoogleSignInPlugin.java

@@ -56,13 +56,13 @@ public void initInstance(
       @NonNull GoogleSignInWrapper googleSignInWrapper) {
     this.messenger = messenger;
     delegate = new Delegate(context, googleSignInWrapper);
-    GoogleSignInApi.setup(messenger, delegate);
+    GoogleSignInApi.setUp(messenger, delegate);
   }
 
   private void dispose() {
     delegate = null;
     if (messenger != null) {
-      GoogleSignInApi.setup(messenger, null);
+      GoogleSignInApi.setUp(messenger, null);
       messenger = null;
     }
   }
@@ -241,6 +241,30 @@ void requestScopes(
         final @NonNull MethodChannel.Result result, final @NonNull List<String> scopes);
   }
 
+  /**
+   * Helper class for supporting the legacy IDelegate interface based on raw method channels, which
+   * handles converting any FlutterErrors (or other {@code Throwable}s in case any non- FlutterError
+   * exceptions slip through) thrown by the new code paths into {@code error} callbacks.
+   */
+  private abstract static class ErrorConvertingMethodChannelVoidResult
+      implements Messages.VoidResult {
+    final @NonNull MethodChannel.Result result;
+
+    public ErrorConvertingMethodChannelVoidResult(@NonNull MethodChannel.Result result) {
+      this.result = result;
+    }
+
+    @Override
+    public void error(@NonNull Throwable error) {
+      if (error instanceof FlutterError) {
+        FlutterError flutterError = (FlutterError) error;
+        result.error(flutterError.code, flutterError.getMessage(), flutterError.details);
+      } else {
+        result.error("exception", error.getMessage(), null);
+      }
+    }
+  }
+
   /**
    * Helper class for supporting the legacy IDelegate interface based on raw method channels, which
    * handles converting any FlutterErrors (or other {@code Throwable}s in case any non- FlutterError
@@ -296,13 +320,13 @@ public void success(Messages.UserData data) {
    * Helper class for supporting the legacy IDelegate interface based on raw method channels, which
    * handles converting responses from methods that return {@code Void}.
    */
-  private static class VoidMethodChannelResult extends ErrorConvertingMethodChannelResult<Void> {
+  private static class VoidMethodChannelResult extends ErrorConvertingMethodChannelVoidResult {
     public VoidMethodChannelResult(MethodChannel.Result result) {
       super(result);
     }
 
     @Override
-    public void success(Void unused) {
+    public void success() {
       result.success(null);
     }
   }
@@ -367,7 +391,7 @@ public void setActivity(@Nullable Activity activity) {
     private void checkAndSetPendingOperation(
         String method,
         Messages.Result<Messages.UserData> userDataResult,
-        Messages.Result<Void> voidResult,
+        Messages.VoidResult voidResult,
         Messages.Result<Boolean> boolResult,
         Messages.Result<String> stringResult,
         Object data) {
@@ -385,7 +409,7 @@ private void checkAndSetPendingSignInOperation(
     }
 
     private void checkAndSetPendingVoidOperation(
-        String method, @NonNull Messages.Result<Void> result) {
+        String method, @NonNull Messages.VoidResult result) {
       checkAndSetPendingOperation(method, null, result, null, null, null);
     }
 
@@ -557,7 +581,7 @@ public void signIn(@NonNull MethodChannel.Result result) {
      * sign back in.
      */
     @Override
-    public void signOut(@NonNull Messages.Result<Void> result) {
+    public void signOut(@NonNull Messages.VoidResult result) {
       checkAndSetPendingVoidOperation("signOut", result);
 
       signInClient
@@ -580,7 +604,7 @@ public void signOut(@NonNull MethodChannel.Result result) {
 
     /** Signs the user out, and revokes their credentials. */
     @Override
-    public void disconnect(@NonNull Messages.Result<Void> result) {
+    public void disconnect(@NonNull Messages.VoidResult result) {
       checkAndSetPendingVoidOperation("disconnect", result);
 
       signInClient
@@ -705,7 +729,7 @@ private String errorCodeForStatus(int statusCode) {
     }
 
     private void finishWithSuccess() {
-      Objects.requireNonNull(pendingOperation.voidResult).success(null);
+      Objects.requireNonNull(pendingOperation.voidResult).success();
       pendingOperation = null;
     }
 
@@ -720,32 +744,35 @@ private void finishWithUserData(Messages.UserData data) {
     }
 
     private void finishWithError(String errorCode, String errorMessage) {
-      Messages.Result<?> result;
-      if (pendingOperation.userDataResult != null) {
-        result = pendingOperation.userDataResult;
-      } else if (pendingOperation.boolResult != null) {
-        result = pendingOperation.boolResult;
-      } else if (pendingOperation.stringResult != null) {
-        result = pendingOperation.stringResult;
+      if (pendingOperation.voidResult != null) {
+        Objects.requireNonNull(pendingOperation.voidResult)
+            .error(new FlutterError(errorCode, errorMessage, null));
       } else {
-        result = pendingOperation.voidResult;
+        Messages.Result<?> result;
+        if (pendingOperation.userDataResult != null) {
+          result = pendingOperation.userDataResult;
+        } else if (pendingOperation.boolResult != null) {
+          result = pendingOperation.boolResult;
+        } else {
+          result = pendingOperation.stringResult;
+        }
+        Objects.requireNonNull(result).error(new FlutterError(errorCode, errorMessage, null));
       }
-      Objects.requireNonNull(result).error(new FlutterError(errorCode, errorMessage, null));
       pendingOperation = null;
     }
 
     private static class PendingOperation {
       final @NonNull String method;
       final @Nullable Messages.Result<Messages.UserData> userDataResult;
-      final @Nullable Messages.Result<Void> voidResult;
+      final @Nullable Messages.VoidResult voidResult;
       final @Nullable Messages.Result<Boolean> boolResult;
       final @Nullable Messages.Result<String> stringResult;
       final @Nullable Object data;
 
       PendingOperation(
           @NonNull String method,
           @Nullable Messages.Result<Messages.UserData> userDataResult,
-          @Nullable Messages.Result<Void> voidResult,
+          @Nullable Messages.VoidResult voidResult,
           @Nullable Messages.Result<Boolean> boolResult,
           @Nullable Messages.Result<String> stringResult,
           @Nullable Object data) {
@@ -764,7 +791,7 @@ private static class PendingOperation {
 
     /** Clears the token kept in the client side cache. */
     @Override
-    public void clearAuthCache(@NonNull String token, @NonNull Messages.Result<Void> result) {
+    public void clearAuthCache(@NonNull String token, @NonNull Messages.VoidResult result) {
       Callable<Void> clearTokenTask =
           () -> {
             GoogleAuthUtil.clearToken(context, token);
@@ -775,7 +802,8 @@ public void clearAuthCache(@NonNull String token, @NonNull Messages.Result<Void>
           clearTokenTask,
           clearTokenFuture -> {
             try {
-              result.success(clearTokenFuture.get());
+              clearTokenFuture.get();
+              result.success();
             } catch (ExecutionException e) {
               @Nullable Throwable cause = e.getCause();
               result.error(