Apply Language Modes to Files With Non-Standard Filenames in VS Code

Have you ever opened a file in VS Code that doesn't have a standard language extension or filename and noticed that the syntax highlighting and other language mode features is missing?

As a trivial example, you might have a Brewfile and want it to have syntax highlighting. Despite being Ruby, without a .rb extension syntax highlighting won't be applied because VS Code doesn't have a way to determine the Brewfile is Ruby. Another example is an AlfredApp Theme file, it has the naming convention of *.alfredappearance but is JSON, so syntax highligthing won't be applied to this file either.

VS Code makes it easy to associate a file with a language mode by adding files.associations to your settings.json. To demonstrate, here's what a configuration for the above examples would look like:

{
  "files.associations": {
    "Brewfile": "ruby",
    "*.alfredappearance": "json"
  }
}

files.associations is an object where each key is a filename or a pattern (glob) of the filename with the value set to the language mode that it represents.

Now whenever you open a Brewfile or an Alfred theme that ends in .alfredappearance, the file will get the correct syntax highlighting and all the features that are available to the language mode!

In the examples I've given for files.associations, syntax highlighting was the only feature highlighted, but setting a file to a language mode gives it access to any functionality that's associated with that language.