All CLA requirements met.

Can this support different default fileicons for the different file-extensions that an extension can associate with a language?

@gjsjohnmurray no it can't (at least at the moment). its implemented like the proposed way from aeschli in this comment #14662 (comment) which only allows one default icon per language definition

Can we use SVG files instead of fonts? Dark and light icons? What's the syntax for both?

Is there any update on this PR? @aeschli is there something wrong with it?

It seems that @Mai-Lapyst got the @aeschli's review point covered in the last commit. Any chance to get this PR landed soon? 😃

Thanks @Mai-Lapyst!

I made some changes.

• use ThemeIcon but dont have it in monaco.d.ts
• use the Use ${iconName) notation in package.json as we already use that notation at other places where icons are referenced

    "languages": [
      {
        "id": "diff",
        "extensions": [ ".diff" ],
        "configuration": "./languages/diff.language-configuration.json",
        "icon": "$(zap)"
      },

• by default show the mode icons if the theme has file icons. Themes can override with the new theme property showLanguageModeIcons
• only show the language icon if none of the variants (light, high contrast) has a language icon. This avoids conflicts when the icon theme uses pngs or fonts with different sizes.

Nice! This is something that we are really looking forward to. Anything preventing this from going in? I'm happy to help if required.

After adding this feature, how difficult will it be to give custom icons based on a specific filename? For example, if developers have a file called test, with no file extension, in their workspace, will this change allow me to give that file a special, custom icon?

I'm looking forward to this. Thank you to the people adding this feature.

@hamirmahal It all builds on the existing ways on how filenames are associated to languages

• When an extension defines a language we currently support extensions, filenames, filenamePatterns and firstLine.
• Additionally users can customize filename to language associations using the setting

 "files.associations": {
    "devcontainer*.json": "jsonc"
  },

@aeschli Ah, okay. Thank you for the response!

After merging this pull request, how will we know in which version of VSCode this feature will be available?

Next endgame is end of January, if this does get deemed ready for merge

I made the following change:
icon no longer points to a ThemeIcon but to light and dark paths that provide the icon (svg, gif, png...).

{
  "contributes": {
    "languages": [
      {
        "id": "latex",
        // ...
        "icon": {
          "light": "./latex.png",
          "dark": "./latex.png"
        }
      }
  ]
}

That simplifies the usage of the new property. It is no longer necessary to also create an icon font and we no longer depend on
contribIcons proposed API (https://raw.githubusercontent.com/microsoft/vscode/main/src/vscode-dts/vscode.proposed.contribIcons.d.ts).

The new property is currently marked as proposed API. That means to try it out, an extension must add

"enabledApiProposals": [ "languageIcon" ]

to its package.json and cannot yet be published to the marketplace.
See https://code.visualstudio.com/api/advanced-topics/using-proposed-api from more details.

I'll bring the API to the API call so I can hopefully remove the proposed API check soon.

See #140047 for the current proposal and implementation

The API is now final, "enabledApiProposals": [ "languageIcon" ] is no longer needed.

Thanks for getting this in.

I just tried the following:

"languages": [
      {
        "id": "plz",
        "aliases": [
          "Please",
          "please"
        ],
        "filenames": [
          "BUILD"
        ],
        "extensions": [
          ".plz",
          ".build_defs",
          ".build"
        ],
        "icon": {
          "light": "./plz_128.png",
          "dark": "./plz_128.png"
        },
        "configuration": "./syntax/language-configuration.json"
      }
]

And the icon defined above is correctly linked to all extensions, but not the BUILD filename. I was looking into the code and https://github.com/jesseweed/seti-ui/blob/master/styles/components/icons/mapping.less#L548 seems to be what takes precedence. Is there a way to override this?

No, that's on purpose.
Specific icons from the file icon theme always win. The language icon is just a fallback for the case a theme does not have a specific icon.

I would recommend filing an issue against the themes if you think the icon they provide needs to be improved.

With Seti it's a bit special at it is generated by us. What we could do is improve our converter. Please file an issue against microsoft/vscode

I see, thanks!