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Contributing to nvim-treesitter

First of all, thank you very much for contributing to nvim-treesitter.

If you haven't already, you should really come and reach out to us on our gitter room, so we can help you with any question you might have!

As you know, nvim-treesitter is roughly splitted in two parts :

  • Parser configurations : for various things like locals, highlights
  • What we like to call modules : tiny lua modules that provide a given feature, based on parser configurations

Depending on which part of the plugin you want to contribute to, please read the appropriate section.

Style Checks and Tests

We haven't implemented any functional tests yet. Feel free to contribute. However, we check code style with luacheck! Please install luacheck and activate our pre-push hook to automatically check style before every push:

luarocks install luacheck
ln -s ../../scripts/pre-push .git/hooks/pre-push

Adding new modules

If you want to see a new functionality added to nvim-treesitter feel free to first open an issue to that we can track our solution! Thus far, there is basically two types of modules:

  • Little modules (like incremental selection) that are built in nvim-treesitter, we call them builtin modules.
  • Bigger modules (like completion-treesitter, or nvim-tree-docs), or modules that integrate with other plugins, that we call remote modules.

In any case, you can build your own module ! To help you started in the process, we have a template repository designed to build new modules here. Feel free to use it, and contact us over on our gitter.

Parser configurations

Contributing to parser configurations is basically modifying one of the queries/*/*.scm. Each of these scheme files contains a tree-sitter query for a given purpose. Before going any further, we highly suggest that you read more about tree-sitter queries.

Each query has an appropriate name, which is then used by modules to extract data from the syntax tree. For now two types of queries are used by nvim-treesitter:

  • highlights.scm: used for syntax highlighting, using the highlight module.
  • locals.scm: used to extract keyword definitions, scopes, references, etc, using the locals module.
  • textobjects.scm: used to define text objects.
  • folds.scm: used to define folds.

For these types there is a norm you will have to follow so that features work fine. Here are some global advices :

  • If your language is listed here, you can install the playground plugin.
  • If your language is listed here, you can debug and experiment with your queries there.
  • If not, you should consider installing the tree-sitter cli, you should then be able to open a local playground using tree-sitter build-wasm && tree-sitter web-ui within the parsers repo.
  • Examples of queries can be found in queries/
  • Matches in the bottom will override queries that are above of them.

If your language is an extension of a language (TypeScript is an extension of JavaScript for example), you can include the queries from your base language by adding the following as the first line of your file.

; inherits: lang1,(optionallang)

If you want to include a language for a given query, but don't want for the queries including the query you qre writing to include it too, you can mark the language as optional (by putting it between parenthesis).

Highlights

As languages differ quite a lot, here is a set of captures available to you when building a highlights.scm query. One important thing to note is that many of these capture groups are not supported by neovim for now, and will not have any effect on highlighting. We will work on improving highlighting in the near future though.

Misc

@comment
@error for error `ERROR` nodes.
@none to disable completely the highlight
@punctuation.delimiter for `;` `.` `,`
@punctuation.bracket for `()` or `{}`
@punctuation.special for symbols with special meaning like `{}` in string interpolation.

Constants

@constant
@constant.builtin
@constant.macro
@string
@string.regex
@string.escape
@string.special
@character
@number
@boolean
@float

Functions

@function
@function.builtin
@function.macro
@parameter

@method
@field
@property

@constructor

Keywords

@conditional
@repeat
@label for C/Lua-like labels
@keyword
@keyword.function
@keyword.operator (for operators that are English words, e.g. `and`, `or`)
@operator (for symbolic operators, e.g. `+`, `*`)
@exception
@include keywords for including modules (e.g. import/from in Python)

@type
@type.builtin
@namespace for identifiers referring to namespaces
@symbol for identifiers referring to symbols
@attribute for e.g. Python decorators

Variables

@variable
@variable.builtin

Text

Mainly for markup languages.

@text
@text.strong
@text.emphasis
@text.underline
@text.strike
@text.title
@text.literal
@text.uri
@text.math (e.g. for LaTeX math environments)
@text.environment (e.g. for text environments of markup languages)
@text.environment.name (e.g. for the name/the string indicating the type of text environment)
@text.reference (for footnotes, text references, citations)

@text.note
@text.warning
@text.danger

Tags

Used for xml-like tags

@tag
@tag.delimiter

Locals

@definition for various definitions
@definition.function
@definition.method
@definition.var
@definition.parameter
@definition.macro
@definition.type
@definition.field
@definition.enum
@definition.namespace for modules or C++ namespaces
@definition.import for imported names

@definition.associated to determine the type of a variable
@definition.doc for documentation adjacent to a definition. E.g.

@scope
@reference
@constructor

Definition Scope

You can set the scope of a definition by setting the scope property on the definition.

For example, a javascript function declaration creates a scope. The function name is captured as the definition. This means that the function definition would only be available WITHIN the scope of the function, which is not the case. The definition can be used in the scope the function was defined in.

function doSomething() {}

doSomething(); // Should point to the declaration as the definition
(function_declaration
  ((identifier) @definition.var)
   (set! "definition.var.scope" "parent"))

Possible scope values are:

  • parent: The definition is valid in the containing scope and one more scope above that scope
  • global: The definition is valid in the root scope
  • local: The definition is valid in the containing scope. This is the default behavior

Folds

You can define folds for a given language by adding a folds.scm query :

@fold

If the fold.scm query is not present, this will fallback to the @scope captures in the locals query.

Injections

Some captures are related to language injection (like markdown code blocks). They are used in injections.scm. You can directly use the name of the language that you want to inject (e.g. @html to inject html).

If you want to dynamically detect the language (e.g. for Markdown blocks) use the @language to capture the node describing the language and @content to describe the injection region.

@{language} ; e.g. @html to describe a html region

@language ; dynamic detection of the injection language (i.e. the text of the captured node describes the language)
@content ; region for the dynamically detected language