RoslynCodeTaskFactory: Log MSB3753 when task class does not implement ITask

[jankratochvilcz]

Summary

RoslynCodeTaskFactory.CreateTask() silently returned null when the inline task class did not implement ITask, causing the engine to emit the generic MSB4060 error. CodeTaskFactory already checks for this and emits the more specific MSB3753 (CodeTaskFactory.NeedsITaskInterface).

Changes

• RoslynCodeTaskFactory.cs: Added null check after Activator.CreateInstance(TaskType) as ITask — logs MSB3753 via the existing _log instance (set during Initialize), matching CodeTaskFactory behavior.
• RoslynCodeTaskFactory_Tests.cs: Added ClassDoesNotInheritFromITask test covering both in-proc and out-of-proc (MSBUILDFORCEINLINETASKFACTORIESOUTOFPROC) paths.

Context

I noticed this when trying to migrate usage of CodeTaskFactory to RoslynCodeTaskFactory and checking for coverage parity between these two factories as part of that.

The CodeTaskFactory equivalent test (CodeTaskFactoryTests.cs) already validates this behavior. This was an oversight in RoslynCodeTaskFactory — the two factories should produce the same diagnostic for this user error.

[Copilot]

Pull request overview

Aligns RoslynCodeTaskFactory diagnostics with CodeTaskFactory by emitting MSB3753 when an inline task class doesn’t implement ITask, instead of failing later with a generic MSB4060.

Changes:

• Add a null-check in RoslynCodeTaskFactory.CreateTask() and log CodeTaskFactory.NeedsITaskInterface (MSB3753) when the created instance can’t be cast to ITask.
• Add an end-to-end unit test validating the MSB3753 behavior for both in-proc and forced out-of-proc inline task factory paths.
• Add a new regression test covering successful execution when the temp directory path does not exist.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
src/Tasks/RoslynCodeTaskFactory/RoslynCodeTaskFactory.cs	Adds MSB3753 logging when the compiled inline task type does not implement ITask.
src/Tasks.UnitTests/RoslynCodeTaskFactory_Tests.cs	Adds coverage for the new MSB3753 behavior and an additional temp-directory regression scenario.

[github-actions]

Security Awareness — LGTM

No security regression. Activator.CreateInstance(TaskType) was already the existing instantiation path; the only addition is a null-guard with error logging. No changes to type loading policy, file operations, or path handling.

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