Fix E_ACCESSDENIED during download if temp is hidden

[chemwolf6922]

Summary of the Pull Request

The winrt::Windows::Storage::StorageFolder::GetFolderFromPathAsync function does not accept folders with hidden or system attributes. To solve that, this PR avoids the GetFolderFromPathAsync call and opens the file stream directly.

PR Checklist

• Closes: cannot use wsl --update to update WSL, nor use wsl --install to install a Linux distribution #40662
• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated if needed and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated if needed
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

Add test UnitTests::UnitTests::DownloadToHiddenSystemTempFolder

[Copilot]

Pull request overview

This PR addresses E_ACCESSDENIED failures during wsl --update / wsl --install downloads when the user’s temp directory has the Hidden/System attributes set, by switching WinRT file operations to a newly-created temp subfolder with those attributes cleared.

Changes:

• Refactors the existing modern distro install unit test logic into a helper so it can be reused by multiple test cases.
• Adds a new unit test that exercises modern distro installation when the temp folder is hidden.
• Updates the WinRT download path selection to use a wsl-downloads subfolder under %TEMP%, explicitly clearing Hidden/System attributes before calling StorageFolder::GetFolderFromPathAsync.

Reviewed changes

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

File	Description
test/windows/UnitTests.cpp	Refactors the ModernDistroInstall test and adds a regression test for hidden temp folders.
src/windows/common/wslutil.cpp	Routes WinRT-based downloads through a temp subfolder with Hidden/System attributes cleared.

[Copilot]

Pull request overview

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

[benhillis]

Looks good maybe just drop the set when it is not needed.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

[OneBlue]

Thank you for doing this !

This is a really weird winrt behavior, but looks like there's no way to disable the attribute check, so let's just work around it.

The current implementation works, but in its current form, we'll always leak the "wsl-downloads folder, and adding logic to delete it would be a bit painful.

Instead I would recommend constructing the path ourselves and then using CreateRandomAccessStreamOnFile , which should allow us to open the file directly without the folder attribute issue.

[OneBlue]

Instead I would recommend constructing the path ourselves and then using CreateRandomAccessStreamOnFile , which should allow us to open the file directly without the folder attribute issue.

Or even better, we could directly use this, that way we can set openDisposition and create the file ourselves

[Copilot]

Pull request overview

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

[OneBlue]

LGTM, couple minor comments