nvim-ts-format

Write your own formatter and formatexpr for any language, made easy with Tree-sitter!

Installation

• Using lazy.nvim

  { 
    "lucario387/nvim-ts-format",
    dependencies = { "nvim-treesitter/nvim-treesitter" },
  }

Usage

• Create some queries for a certain language, using the captures listed below, save it as queries/{lang}/formats.scm. For r C, it's queries/c/formats.scm, for *.js files it will be queries/javascript/formats.scm.
  • Set formatexpr for certain filetypes that they want to use, for example, enabling for json and C
  • Use require('nvim-ts-format').format_buf(bufnr) to fully a buffer

vim.api.nvim_create_autocmd("FileType", {
  pattern = { "json", "c" },
  callback = function()
    vim.bo.formatexpr = "v:lua.require('nvim-ts-format').formatexpr()"
  end
})

Supported Captures

This section assumes you have grasps the basics of

• Treesitter queries
• Lua patterns

Summary for the query knowledge: Click to expand!

A query will be used

• For captures, all captures used inside queries/*/formats.scm files must be of the listed below.

  • If possible, you should avoid capturing quantifiers due to Neovim quantifiers capture issues (i.e. ())
  • A capture is considered private if its name started with _. If you want to use other captures for other purposes, such as filtering through predicates, please use private captures

• For predicates, directives, these are some of the more useful for writing queries with this plugin.

  • (#set! ...): This will be used for @format.ignore and @format.indent.begin
  • (#eq? @capture "abcdef"), (#eq? @capture1 @capture2): whether the text content of @capture is abcdef, or check whether the text content of @capture1 and @capture2 are the same
  • (#lua-match? @capture "") and (#vim-match? @capture ""): whether the text content of @capture matches a lua/vim regular expression pattern
  • (#has-type? @capture a b c) and (#not-has-type? @capture a b c): If the syntax node's name associated with @capture is a, b, c, (or not)
  • For the rest, you can check out the list of supported directives and predicates at
    • :h treesitter-predicates
    • :h treesitter-directives

Below is the list of accepted captures:

@format.remove

If a syntax node is captured with this, it will be removed from the end file.

Example: Removing trailing ; from js statements

(experession_statement ";" @format.remove)

@format.ignore, @format.keep

These captures will try to keep the content as is.

@format.ignore will also ignore any other captures and stylings applied to this syntax node, while @format.keep will not.

• @format.ignore: Ignore everything. Keep the stylings as is
  • Side-effect: newlines may be incorrect, as the syntax node doesn't have newlines at the end of it. To offset this, use (#set! @format.ignore append-newline)

Example: Ignoring nodes in between a comment with start-ignore and end-ignore

(
  (comment) @_start
  .
  (_) @format.ignore
  .
  (comment) @_end
  (#lua-match? @_start "start%-ignore")
  (#lua-match? @_end "end%-ignore")
)

• @format.keep: Telling the formatter to keep the contents of this syntax node as is. This still applies all other captures onto a syntax node, such as prepending newlines/spaces before the node.

Most used: Keep the content of a string

(string) @format.keep

@format.indent.begin, @format.indent.end, @format.indent

• @format.indent.begin: Has 2 usages
  • Adds an extra indentation level to all nodes after it that's under the same parent. Also inserts a newline
  • With a directive (#set! format.conditional), this will instead be used to conditionally add newlines if it deems there's too many check for maxwidth and clump all to a line or not by doing (#set! format.conditional). By default it always add a new line.
    • This will not take effect if :h textwidth is not set. It will fully ignore those indents.
• @format.indent.end: Subtracts an extra indentation level to all nodes after it that's under the same parent. Usage is rarely needed, but this is kept for certain languages/scopes configurations.
• @format.indent: Used only for calculating indentation level while handling certain sections of the file, unused if formatting the entire file.You can ignore this.

@format.indent.dedent, @format.indent.zero

These captures only take effects if the node is in a line with only whitespaces/tabs

• @format.indent.dedent: Remove indent_width spaces, or 1 tab from start of current line if the node is the start of the line. This should be used in combination with @format.indent.end, to mark the end of an extra level

Example: Usage in C

(compound_statement
  "{" @format.indent.begin
  "}" @format.indent.dedent)

We will get this code before and after formatting

-{ some_code; }
+{
+  some_code;
+}

• @format.indent.zero: Remove all prefixing whitespace/tabs from current line if this is the i.e. #ifdef in C

[
  "#define"
  "#ifdef"
  "#ifndef"
  "#endif"
] @format.indent.zero

Example: The C code below after applying the format

int main(){
-  #define FOO BAR
+#define FOO BAR
}

@format.append-newline, @format.append-space, @format.cancel-append

Append newlines/spaces, or ignore it

@format.append-newline will take precedence over @format.append-space

Example: Adding newlines after each statement in C, and spaces after keywords and

[
  (primitive_type)
  (type_identifier)
] @format.append-space
(expression_statement) @format.append-newline

in combination with all C example aboves, will lead to

int main(){
  Foo a;
}

@format.prepend-newline, @format.prepend-space, @format.cancel-prepend

Prepend newlines/spaces, or ignore it for certain combinations

@format.prepend-newline will take precedence over @format.prepend-space

Credits

• nvim-treesitter: It was from here that I wanted to develop my own generic formatter
• Topiary: They were first to try this, but it was very hard to adopt this into Neovim, so I wanted to create one. Also, TOML example queries were inspired from their queries