File access from web extensions is broken

[thegecko]

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I believe a change has been made in the file scheme used in Codespaces and the github.dev versions of VS Code for web which has broken the ability for Local/Web extensions (those installed in the web extension host) to effectively use file paths or use the workspace.fs.* APIs.

For example, a debug adapter running in the web extension uses paths which are no longer recognised by the UI.

To recreate this, install the mock-debug extension in the web extension host of the VSCode for web flavours and observe the differences:

vscode.dev
The debugger runs in the browser and accesses files using the browser filesystem API. All works as expected.

@vscode/test-web
This runs on a developer's machine and I believe should mimic how codespaces/github.dev work. This works as expected.

github.dev
The debugger fails when setting breakpoints or opening files with:

Uncaught (in promise) Error (FileSystemError): Unable to read file '/vscode-vfs://github%2b7b2276223a312c22726566223a7b2274797065223a362c226964223a226d61696e227d7d/arm-debug/mock-debug/readme.md' (Unavailable (FileSystemError): Error: No file system handle registered (/vscode-vfs:/))

codespaces
You must ensure mock-debug is installed "Locally" in the web extension host, (by default it is installed in the codespace host and will work correctly) by modifying the settings:

{
    "remote.extensionKind": {
        "ms-vscode.mock-debug": [
            "ui"
        ]
    }
}

In the web extension host, similar errors are seen as github.dev:

Uncaught (in promise) Error (FileSystemError): Unable to read file '/workspaces/mock-debug/readme.md' (Unavailable (FileSystemError): Error: No file system handle registered (/workspaces))

Unfortunately codespaces and github.dev are also the only environments you cannot sideload or debug extensions in, so debugging this issue is extremely challenging.

I've tried reformatting paths prepending vscode-remote:// and variations on the root fspath but this doesn't work.

How should a debug adapter format paths so they can be opened by the UI in codespaces/github.dev when the scheme and authority aren't present?

[thegecko]

Any comments on this issue?

[thegecko]

To format paths so they can be opened by the UI in codespaces/github.dev, you can try using the vscode-uri library to convert the file path to a vscode.Uri object

Thanks, extension developers have the ability to do that when they have control over the paths (e.g. by injecting a filereader for a debugger as done here: https://github.com/microsoft/vscode-mock-debug/blob/main/src/activateMockDebug.ts#L187).
However, this issue exists between the debug adapter and debug UI in VSCode and I can't work out how to format the correct string for the debug adapter protocol path contents as it doesn't transfer a URI object. I'm not sure it's even possible.

If this doesn't resolve the issue, you may need to reach out to the VS Code support team or GitHub support

This is also raised on VS Code here: microsoft/vscode#171991

I was also under the impression this discussion IS GitHub support!

...try using workspace URIs instead of file paths while accessing files in your extension code

This isn't possible, paths in the debug adapter protocol are strings and get passed straight to the VS Code UI

The format of the path to be used must remove the scheme prefix

I've successfully done this with the paths for reading files:
https://github.com/thegecko/vscode-mock-debug/blob/mock-debug-test/src/activateMockDebug.ts#L215

But can't see how to modify paths coming back from the debugger :/

Unfortunately, without additional details, it is difficult to provide a specific solution to this problem

To that end, I've created instructions and a demo example extension to recreate the issue here:

https://github.com/thegecko/vscode-web-test

I'm very keen to get an update on this or at least to confirm if the issue is with the adapter (there may be a certain path format to use), VS Code or codespaces.

[thegecko]

I can confirm this is a string formatting issue. A fix for mock-debug has been implemented here:

microsoft/vscode-mock-debug#93