Add ftplugin/astro.vim and autoload/astro.vim

[romainl]

This pull request adds two files: ftplugin/astro.vim and autoload/astro.vim.

Overview

ftplugin/astro.vim enables/fine-tunes the following features:

• autoformatting and manual formatting, via formatoptions,
• project-wide navigation, via path, define, include, includeexpr,suffixesadd, and b:astro_paths,
• matching with %, via matchpairs, b:match_ignorecase, and b:match_words,
• keyword definition, via iskeyword,
• default HTML comment format, via comments and commentstring,
• scope-specific comment format, via a CursorMoved autocommand.

autoload/astro.vim hosts the following support functions:

• astro#IdentifyScope() and astro#Comments(), define the proper comments and commentstring for the current scope,
• astro#CollectPathsFromConfig(), collects aliases defined in tsconfig.json for use in the function below,
• astro#AstroInclude(), replaces aliases in filenames for :find, gf, etc.

Details

Project-wide navigation

• path is set according to https://docs.astro.build/en/core-concepts/project-structure/#directories-and-files.

  It allows doing gf on "src/components/Foo.astro", "./Foo.astro", "../bar/Baz.astro" in the front matter. It also allows doing :find *Foo<Tab> for the simple cases.

  It also helps resolving includes for include/definition search.

• suffixesadd is a mix of all the values found in $VIMRUNTIME/ftplugin/{javascript,typescript,css,sass,html}.vim, plus some Astro-specific ones.

  It tells Vim what extensions to try for extension-less filenames. This allows doing gf on <Foo /> in a template for the simple cases.

• b:astro_paths is populated by astro#CollectPathsFromConfig() with a list of all the aliases defined in tsconfig.json or jsconfig.json. This is not directly useful for the user but useful for the next option.

• includeexpr is executed if the target is not found. It is bound to astro#AstroInclude(), which replaces the alias in the filename with the corresponding path.

  So, in addition to the simple cases, it also handles cases like "@components/Foo.astro" for gf, include/definition search, etc.

• include is set to a value that should work for ESM imports like import Foo from "..., import type Foo from "..., or import "....

  It allows things like [<C-i> on a type, etc.

• define is set to a value that mixes the default values for JavaScript and SASS.

  It should help locating definitions in local and included files with commands like [D or :dsearch.

Scoped comment formats

astro#Comments() set comments and commentstring to the appropriate value for the current scope. The implementation honestly looks like it should be slow but it only takes a couple of milliseconds and I didn't notice any performance issue.

I did this for tpope/commentary, which uses commentstring.

Note: it only covers SASS/SCSS/CSS, JS/TS, and HTML at the moment.

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Tested in Vim 9.0.270 and Vim 9.0472 on a Mac.

[wuelnerdotexe]

Hi! @romainl - first, sorry for leaving so much time without approving your excellent contribution.

Thank you very much for contributing your knowledge to this little plugin, everything seems incredible to me. 🤩