[extension activation] Extension not activated on certain contribution points.

[ejgallego]

Dear VSCode devs,

this is a follow up to microsoft/vscode-discussions#901 , pinging you here as I believe there may be a bug, not sure

• VS Code Version: 1.84.2
• OS Version: Linux

Starting with VSCode 1.75 (I believe), when extensions contribute a language, they don't need to declare it in activation events. This works well for our extension .v files (cc: https://github.com/ejgallego/coq-lsp ), however, we'd also like our extension to be activated on certain markdown files ending in .mv.

This is the relevant part of our package.json

  "contributes": {
    "languages": [
      {
        "id": "markdown",
        "aliases": [
          "Markdown"
        ],
        "extensions": [
          ".mv"
        ]
      }
    ],

The situation here is strange:

• if I activate the extension by other means, .mv files work fine and are recognized by our language server.
• if I start from an empty VSCode workspace, and I open just a .mv file, the extension won't be activated.
• The extension is activated normally by .v files, which are also declared on contributes.language

I'm not sure if this is intended or a bug, but given the recent changes to activation in 1.75 I thought I'd signal this to you folks.

Steps to reproduce

1. build coq-lsp main branch, launch the extension in dev mode
2. open an .mv file, (set examples as your workspace for example), the extension will be activated
3. close VSCode, remove the onLanguage:markdown activation event
4. repeat step 2, now the extension won't be activated.

[vscodenpa]

Thanks for creating this issue! It looks like you may be using an old version of VS Code, the latest stable release is 1.84.2. Please try upgrading to the latest version and checking whether this issue remains.

Happy Coding!

[joyceerhl]

We will only do an implicit activation for "main" language contributions, i.e. contributions that include the language configuration: #173992, #179287. This behavior is currently as designed, I'd suggest to declare a standard onLanguage: activation event for your scenario.

[ejgallego]

Thanks a lot for the information @joyceerhl , I was not aware of the notion of this rule, it makes sense!

I'll actually play with the alias property too, as our language is really an alias, but so far the onLanguage plus the file selection rule is working as we desire as our extension is only activated for .mv files and not for .md files.

I checked the API docs, maybe this could be documented more directly?

I was looking here https://code.visualstudio.com/api/references/activation-events#onLanguage

If so let me know and I'll be happy to prepare a documentation PR.

[joyceerhl]

Please feel free to send a PR, thank you!