From a4916409c252cad0b310665b83040b25450f5526 Mon Sep 17 00:00:00 2001
From: John Schanck <jschanck@mozilla.com>
Date: Wed, 12 Feb 2025 02:12:58 +0000
Subject: [PATCH] Bug 1945969 - part 4: simplify android implementation of
 RecvIsUVPAA. r=keeler

Differential Revision: https://phabricator.services.mozilla.com/D236884
---
 dom/webauthn/WebAuthnTransactionParent.cpp | 52 +++++++++++-----------
 1 file changed, 26 insertions(+), 26 deletions(-)

diff --git a/dom/webauthn/WebAuthnTransactionParent.cpp b/dom/webauthn/WebAuthnTransactionParent.cpp
index a44811c74a23..025ef2bbc9ef 100644
--- a/dom/webauthn/WebAuthnTransactionParent.cpp
+++ b/dom/webauthn/WebAuthnTransactionParent.cpp
@@ -42,6 +42,8 @@ void WebAuthnTransactionParent::DisconnectTransaction() {
 mozilla::ipc::IPCResult WebAuthnTransactionParent::RecvRequestRegister(
     const WebAuthnMakeCredentialInfo& aTransactionInfo,
     RequestRegisterResolver&& aResolver) {
+  MOZ_ASSERT(NS_IsMainThread());
+
   if (!mWebAuthnService) {
     mWebAuthnService = do_GetService("@mozilla.org/webauthn/service;1");
     if (!mWebAuthnService) {
@@ -202,6 +204,8 @@ mozilla::ipc::IPCResult WebAuthnTransactionParent::RecvRequestRegister(
 mozilla::ipc::IPCResult WebAuthnTransactionParent::RecvRequestSign(
     const WebAuthnGetAssertionInfo& aTransactionInfo,
     RequestSignResolver&& aResolver) {
+  MOZ_ASSERT(NS_IsMainThread());
+
   if (!mWebAuthnService) {
     mWebAuthnService = do_GetService("@mozilla.org/webauthn/service;1");
     if (!mWebAuthnService) {
@@ -344,6 +348,8 @@ mozilla::ipc::IPCResult WebAuthnTransactionParent::RecvRequestSign(
 }
 
 mozilla::ipc::IPCResult WebAuthnTransactionParent::RecvRequestCancel() {
+  MOZ_ASSERT(NS_IsMainThread());
+
   if (mTransactionId.isNothing()) {
     return IPC_OK();
   }
@@ -354,6 +360,8 @@ mozilla::ipc::IPCResult WebAuthnTransactionParent::RecvRequestCancel() {
 
 mozilla::ipc::IPCResult WebAuthnTransactionParent::RecvRequestIsUVPAA(
     RequestIsUVPAAResolver&& aResolver) {
+  MOZ_ASSERT(NS_IsMainThread());
+
 #ifdef MOZ_WIDGET_ANDROID
   // Try the nsIWebAuthnService. If we're configured for tests we
   // will get a result. Otherwise we expect NS_ERROR_NOT_IMPLEMENTED.
@@ -374,33 +382,24 @@ mozilla::ipc::IPCResult WebAuthnTransactionParent::RecvRequestIsUVPAA(
   }
 
   // The GeckoView implementation of
-  // isUserVerifiyingPlatformAuthenticatorAvailable does not block, but we must
-  // call it on the main thread. It returns a MozPromise which we can ->Then to
-  // call aResolver on the IPDL background thread.
-  //
-  // Bug 1550788: there is an unnecessary layer of dispatching here: ipdl ->
-  // main -> a background thread. Other platforms just do ipdl -> a background
-  // thread.
+  // isUserVerifiyingPlatformAuthenticatorAvailable dispatches the work to a
+  // background thread and returns a MozPromise which we can ->Then to call
+  // aResolver on the current thread.
   nsCOMPtr<nsISerialEventTarget> target = GetCurrentSerialEventTarget();
-  nsCOMPtr<nsIRunnable> runnable(NS_NewRunnableFunction(
-      __func__, [target, resolver = std::move(aResolver)]() {
-        auto result = java::WebAuthnTokenManager::
-            WebAuthnIsUserVerifyingPlatformAuthenticatorAvailable();
-        auto geckoResult = java::GeckoResult::LocalRef(std::move(result));
-        MozPromise<bool, bool, false>::FromGeckoResult(geckoResult)
-            ->Then(
-                target, __func__,
-                [resolver](
-                    const MozPromise<bool, bool, false>::ResolveOrRejectValue&
-                        aValue) {
-                  if (aValue.IsResolve()) {
-                    resolver(aValue.ResolveValue());
-                  } else {
-                    resolver(false);
-                  }
-                });
-      }));
-  NS_DispatchToMainThread(runnable.forget());
+  auto result = java::WebAuthnTokenManager::
+      WebAuthnIsUserVerifyingPlatformAuthenticatorAvailable();
+  auto geckoResult = java::GeckoResult::LocalRef(std::move(result));
+  MozPromise<bool, bool, false>::FromGeckoResult(geckoResult)
+      ->Then(target, __func__,
+             [resolver = std::move(aResolver)](
+                 const MozPromise<bool, bool, false>::ResolveOrRejectValue&
+                     aValue) {
+               if (aValue.IsResolve()) {
+                 resolver(aValue.ResolveValue());
+               } else {
+                 resolver(false);
+               }
+             });
   return IPC_OK();
 
 #else
@@ -433,6 +432,7 @@ mozilla::ipc::IPCResult WebAuthnTransactionParent::RecvRequestIsUVPAA(
 void WebAuthnTransactionParent::ActorDestroy(ActorDestroyReason aWhy) {
   // Called either by Send__delete__() in RecvDestroyMe() above, or when
   // the channel disconnects. Ensure the token manager forgets about us.
+  MOZ_ASSERT(NS_IsMainThread());
 
   if (mTransactionId.isSome()) {
     DisconnectTransaction();