feat: custom file formats in file content loader

[rgodha24]

Changes

• changes only the file() content layer loader.
• adds native support for yaml data sources
• adds support for custom (e.g. toml, csv) data formats by passing in a custom parsing function
• adds support for nested data in a file
  • e.g. {"dogs": [{...}], "cats":[{...}]} can be in one file by parsing a parse function like (text) => JSON.parse(text).cats

Testing

I added tests for a file loader with a yaml source, a toml source, and a nested json source. the toml source is also nested (that's the only way toml can be used in this scenario).

Docs

This definitely will need doc updates.
some parts that will be out of date:

• https://5-0-0-beta.docs.astro.build/en/guides/content-collections/#when-not-to-create-a-collection mentions no toml support directly
• https://5-0-0-beta.docs.astro.build/en/guides/content-collections/#built-in-loaders needs to be updated with yaml, nested, and different format examples

I would definitely be willing to contribute docs for this feature

/cc @withastro/maintainers-docs

[changeset-bot]

🦋 Changeset detected

Latest commit: 1fb4e2d

The changes in this PR will be included in the next version bump.

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[github-actions]

This PR is blocked because it contains a minor changeset. A reviewer will merge this at the next release if approved.

[ascorbic]

This is a great addition, thanks

[sarah11918]

Thank you, @rgodha24 , this looks like an amazingly helpful addition to the file() loader!

I've added some comments and questions here about making a helpful changeset, which can also provide the basis for the documentation we'll need before this feature is released.

Mostly, my suggestions here are to give you an example of the kind of text/explanation I'd expect to see for this. I am the writer/editor, not the person who knows the feature, so it's up to you to help make this actually correct and meaningful! My suggestions are just to give you a model to use! Please do correct/improve as necessary!

Also, for @ascorbic - I've noticed this is for the main branch. Just checking that this will be for a minor 4.x release, and is not exclusively for the beta? This just determines exactly where/how we add to docs!

[rgodha24]

tysm for the review on the changeset! I implemented all of your suggestions.

Also, for @/ascorbic - I've noticed this is for the main branch. Just checking that this will be for a minor 4.x release, and is not exclusively for the beta? This just determines exactly where/how we add to docs!

I think this should be for the 5.0 release. Does that mean the PR should be merging into next?

[ascorbic]

@rgodha24 yes, if it's just for 5.0 then it'll need to be rebased on next

[rgodha24]

@rgodha24 yes, if it's just for 5.0 then it'll need to be rebased on next

that was so painful but it should be good for review now!

[ascorbic]

This looks great. Thanks for sorting it out!