Web VS Code extensions cannot activate `ms-vscode.wasm-wasi-core`

[jacbz]

When writing a web-only VS Code extension, i.e. with a package.json that only defines a "browser" entrypoint, the extension will not activate when depending on ms-vscode.wasm-wasi-core:

"extensionDependencies": [
    "ms-vscode.wasm-wasi-core"
]

Minimal working example:

• Install the WASI based WebAssembly Execution Engine from the Marketplace.
• Download the official lsp-web-extension-sample example.
• Add ms-vscode.wasm-wasi-core as an extension dependency and run.
• The extension will not activate and will display the error:

  Cannot activate the 'lsp-web-extension-sample' extension because it depends on the 'WASI based WebAssembly Execution Engine' extension, which is not loaded. Would you like to reload the window to load the extension?
  

  Reloading the window does not fix the issue.

Tested on Mac (with the default "Run Web Extension" launch option; VS Code 1.94.0, on Sonoma 14.6.1), and also within a self-hosted web environment.

[CareyJWilliams]

FWIW I've recently noticed this behaviour as well but hadn't quite got to the point of investigation where I felt comfortable raising an issue just yet (as opposed to believing it was user error on my part).

The only thing I can add to the above is that I can get a node based extension using WASM and WASI Core working, but anything browser (extensionDevelopmentKind=web) based does seem to exhibit the above.

[jacbz]

Me too! I've been building a Rust language server compiled to WebAssembly. It works fine in Node, but on the Web, the client seems to have trouble communicating with the server (sendRequest does not reach the server). Weirdly enough, the server can communicate with the client just fine. I'm wondering if these issues are related.

[dbaeumer]

I never tried to run it in the web extension host on the desktop app. I always test the web stuff inside a browser. Can you load the extension into the browser. An example that does this is here: https://github.com/microsoft/vscode-extension-samples folder wasm-language-server

[jacbz]

The issue also occurs in a browser – I'm running an instance of openvscode-server

[CareyJWilliams]

I never tried to run it in the web extension host on the desktop app. I always test the web stuff inside a browser. Can you load the extension into the browser. An example that does this is here: https://github.com/microsoft/vscode-extension-samples folder wasm-language-server

I can sideload things, like this sample, into vscode.dev just fine - the WASI dep is automatically installed and the extension works just fine. It's just the web extension host on the desktop app that's proving problematic for me, which I appreciate probably isn't the primary use case - but it's a shame that it doesn't work.

[dbaeumer]

I will have a look to see why this is failing. One reason might be the following:

• since the wasm-wasi-core extension has a main entry it will very likely be loaded as a desktop extension
• when the lsp extension is loaded as a web extension it will fail since dependencies need to be in the same extension host.

[dbaeumer]

@jrieken do we have a way to force an extension into the web extension host on the desktop?

[jrieken]

Yeah, only having the browser entry point in package.json should force you into the desktop web EH. Wild, qualified guessing that you might wanna restart VS Code with --enable-coi because on desktop cross original isolation is not enabled by default

[CareyJWilliams]

Thank you @dbaeumer , @jrieken. I've managed to get somewhere with the above steps combined.

First, I downloaded a copy of wasm-core and modified its package.json to remove the "main" entry point. Installing that modified version got me past the dependency error but I then also needed to run VS Code with --enable-coi for message passing to start functioning properly. I haven't played around in great depth, but it looks like everything works "as it should" at that point. It's a shame it's not a little easier to do this, but I'm delighted to know it can be done.

[jacbz]

Thank you @dbaeumer , @jrieken. I've managed to get somewhere with the above steps combined.

First, I downloaded a copy of wasm-core and modified its package.json to remove the "main" entry point. Installing that modified version got me past the dependency error but I then also needed to run VS Code with --enable-coi for message passing to start functioning properly. I haven't played around in great depth, but it looks like everything works "as it should" at that point. It's a shame it's not a little easier to do this, but I'm delighted to know it can be done.

That works! However, I'm unable to enable COI with Visual Studio Code Server because --enable-coi is not an option there. ?vscode-coi does not work either – anyone have a workaround?

[sxlijin]

Bump: just ran into this after 2h of debugging.

Something I'm confused about: is WASI supposed to work in web extensions? I don't really understand how WASI code can run in a browser sandbox.