Add error message when invoking async methods synchronously in JSInterop

[ernest-koguc]

Add error message when invoking async methods synchronously in JSInterop

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Added error message indicating root cause issue when tyring to invoke async method synchronously through js interop.

Description

This pull request updates the DotNetDispatcher in JSInterop to indicate root issue when asynchronous .NET methods are invoked synchronously from JavaScript. It introduces a runtime check that throws an exception if an async method is invoked synchronously. The changes also add a targeted unit test to verify this behavior.

• Added a check in DotNetDispatcher.InvokeSynchronously to throw an InvalidOperationException if an async method is invoked synchronously, guiding users to use BeginInvokeDotNet for async methods.
• Introduced the helper method IsAsyncMethod using the AsyncStateMachineAttribute to reliably detect async methods.
• Updated method signatures and call sites to pass an isAsyncContext flag, distinguishing between sync and async invocation contexts. This is needed because InvokeSynchronously is used by both sync and async version. [1] [2] [3]
• Added System.Runtime.CompilerServices import to support async method detection.
  Added a unit test CannotInvokeAsyncMethodSynchronously in DotNetDispatcherTest.cs to verify that attempting to invoke an async method synchronously throws the correct exception and message.

Fixes #46811

[dotnet-policy-service]

Thanks for your PR, @@ernest-koguc. Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[ernest-koguc]

@dotnet-policy-service agree

[pavelsavara]

ideally this would be roslyn analyzer, not runtime change

[Copilot]

Pull Request Overview

This PR adds validation to prevent synchronous invocation of asynchronous JSInvokable methods. The change detects when an async method is called through the synchronous DotNetDispatcher.Invoke path and throws a helpful error message directing users to use BeginInvokeDotNet instead.

• Introduces async method detection using AsyncStateMachineAttribute
• Updates InvokeSynchronously to accept an isAsyncContext parameter to distinguish between sync and async invocation paths
• Adds validation that throws InvalidOperationException when attempting to invoke async methods synchronously

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
DotNetDispatcher.cs	Adds IsAsyncMethod helper and async/sync context validation to prevent misuse of async methods in synchronous invocation paths
DotNetDispatcherTest.cs	Adds test case CannotInvokeAsyncMethodSynchronously to verify the new validation behavior

[Copilot]

Corrected spelling of 'SomeInteralType' to 'SomeInternalType'.

Suggested change

	internal class SomeInteralType
	internal class SomeInternalType

[ernest-koguc]

ideally this would be roslyn analyzer, not runtime change

But then it would be a change in dotnet/razor repo right? Should I close this one then?