test-repo/changelog_unreleased/api/17331.md

Add isSupported function support for languages API (#17331 by @JounQin, #17490 by @fisker)

Previously, languages API for custom plugins only supported inferring parser based on the file basename or extension.

Prettier main added isSupported: (options: { filepath: string }) => boolean function to allow plugin check if file is supported based on the full path (eg: files in a specific directory).

:::note

Prettier can not ensure that filepath exists on disk.
When using from APIs(eg: prettier.format()), Prettier can not ensure it's a valid path either.

:::

If no isSupported provided, it just behaves the same way as before.

export const languages = [
  {
    name: "foo",
    parsers: ["foo"],
    isSupported: ({ filepath }) => filepath.includes(".foo"),
  },
];