Also, I recognize adding another dependency is not ideal for what is essentially a minor feature, but toml is quite light.

@jorgegonzalez how about @iarna/toml? it is actively maintained, and it is the only js package support toml 0.5.0 at the time
https://github.com/iarna/iarna-toml

It’s also much smaller slightly bigger than toml when bundled.

(packagephobia tells you how big a package is when installed on your computer, while bundlephobia tells you how big it is when bundled+minified(+gzipped).)

@foray1010 I'll use @iarna/toml if @j-f1 will allow the size increase 🙏

Thanks @ikatyang for upgrading cosmiconfig!

Should be fine 👍

Not sure why it's failing on node4 🤔

Ah I see.

I think you could use a snapshot in that test, which would save having to create an object to match against.

I'll let other maintainers to decide if we should merge it as I hesitate about adding another config format. If someone wants to add support for other format later, what should we do?

I'm thinking of if we should make loaders be part of plugins so that people can use whatever format they want.

I understand the hesitance to add another format, and this is indeed an opinionated PR. Personally, I would love to see the JavaScript community embrace TOML configuration files more, as it is subjectively superior to both YAML and JSON configurations, and Prettier has the opportunity to lead the community in this. I suspect more users would also lean toward this format if they were given the chance to try it.

As linked in #4845:

Some reasons why TOML is better than YAML for configuration files: https://arp242.net/weblog/yaml_probably_not_so_great_after_all.html

Some arguments against JSON as a configuration language: https://www.lucidchart.com/techblog/2018/07/16/why-json-isnt-a-good-configuration-language/

There's not a huge value-add imo since prettier config files are very small and you're unlikely to need comments in them, but since the work is already done let's merge it 👍

Thank you for contributing to Prettier!