When using types, why is it necessary to specify a noop files?

[magicmark]

@chriskuehl

I'd expect something like this to match my stuff:

-   repo: https://github.com/prettier/prettier
    sha: 1.10.2
    hooks:
    -   id: prettier
        name: prettier (scss, markdown)
        types: [markdown, scss]

As evidenced, it doesn't: https://i.fluffy.cc/mMkBxvs5XF8Lbf8bxxXFRxWClBk8Cg58.html

This is because we apparently also need to add a files: ''

Is this behavior intentional?

From reading the docs, it's not obvious that this is the case - maybe we could clarify this? :)

Thanks!

EDIT: Looks like this might just be #707

[asottile]

Looks like there's ~3 misunderstandings on your part here -- I'll highlight them in the docs for you :)

Neither that config, nor that config with files: '' should match anything:

From this:

types and files are evaluated with AND when filtering. Tags within types are also evaluated using AND.

That is, if you have types: [scss, markdown] you're asking for all files which are both markdown and scss.

Additionally, defaults:

From this

(this is for .pre-commit-config.yaml)

files (optional) override the default pattern for files to run on.
types (optional) override the default file types to run on

That is, it'll inherit any value specified in the repository manifest and only if you override it will that change your outcome.

The defaults are as you'd expect. From this:

files: (optional: default '') the pattern of files to run on. new in 0.15.0: now optional.
types: (optional: default [file]) list of file types to run on.

That is, without specifying anything in .pre-commit-hooks.yaml or .pre-commit-config.yaml you'd match all files.

The third piece to the puzzle is the defaults provided by the manifest:

from here:

    # From https://github.com/prettier/prettier/blob/133303f47a30f6b3e46ffdf9d5c2d6609d65c416/src/options.js#L32-L42
    files: \.(css|less|scss|html|ts|tsx|graphql|gql|json|js|jsx)$

It's likely that this regex hasn't been updated as prettier has learned how to work on other file types. Probably worth a PR at the very least?

prettier originally used types, but it supports a wide variety of things and so it was switched to using files -- here's the relevant issue : prettier/prettier#2745

Putting it together, your manifest as written is asking for:

• filenames that match \.(css|less|scss|html|ts|tsx|graphql|gql|json|js|jsx)$
• AND files that are markdown
• AND files that are scss

So an empty set.

You may also be interested in this issue, though there are no current plans or ideas for implementation: #607

Thanks for the issue -- hope this was helpful.

[magicmark]

I see, thanks!

As suggested: prettier/prettier#4021