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helix/book/src/languages.md
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1# Languages
3Language-specific settings and settings for language servers are configured
4in `languages.toml` files.
6## `languages.toml` files
8There are three possible `languages.toml` files. The first is compiled into
9Helix and lives in the [Helix repository](https://github.com/helix-editor/helix/blob/master/languages.toml).
10This provides the default configurations for languages and language servers.
12You may define a `languages.toml` in your [configuration directory](./configuration.md)
13which overrides values from the built-in language configuration. For example
14to disable auto-LSP-formatting in Rust:
16```toml
17# in <config_dir>/helix/languages.toml
19[[language]]
20name = "rust"
21auto-format = false
22```
24Language configuration may also be overridden local to a project by creating
25a `languages.toml` file under a `.helix` directory. Its settings will be merged
26with the language configuration in the configuration directory and the built-in
27configuration.
29## Language configuration
31Each language is configured by adding a `[[language]]` section to a
32`languages.toml` file. For example:
34```toml
35[[language]]
36name = "mylang"
37scope = "source.mylang"
38injection-regex = "mylang"
39file-types = ["mylang", "myl"]
40comment-token = "#"
41indent = { tab-width = 2, unit = " " }
42language-server = { command = "mylang-lsp", args = ["--stdio"], environment = { "ENV1" = "value1", "ENV2" = "value2" } }
43formatter = { command = "mylang-formatter" , args = ["--stdin"] }
44```
46These configuration keys are available:
48| Key | Description |
49| ---- | ----------- |
50| `name` | The name of the language |
51| `scope` | A string like `source.js` that identifies the language. Currently, we strive to match the scope names used by popular TextMate grammars and by the Linguist library. Usually `source.<name>` or `text.<name>` in case of markup languages |
52| `injection-regex` | regex pattern that will be tested against a language name in order to determine whether this language should be used for a potential [language injection][treesitter-language-injection] site. |
53| `file-types` | The filetypes of the language, for example `["yml", "yaml"]`. See the file-type detection section below. |
54| `shebangs` | The interpreters from the shebang line, for example `["sh", "bash"]` |
55| `roots` | A set of marker files to look for when trying to find the workspace root. For example `Cargo.lock`, `yarn.lock` |
56| `auto-format` | Whether to autoformat this language when saving |
57| `diagnostic-severity` | Minimal severity of diagnostic for it to be displayed. (Allowed values: `Error`, `Warning`, `Info`, `Hint`) |
58| `comment-token` | The token to use as a comment-token |
59| `indent` | The indent to use. Has sub keys `tab-width` and `unit` |
60| `language-server` | The Language Server to run. See the Language Server configuration section below. |
61| `config` | Language Server configuration |
62| `grammar` | The tree-sitter grammar to use (defaults to the value of `name`) |
63| `formatter` | The formatter for the language, it will take precedence over the lsp when defined. The formatter must be able to take the original file as input from stdin and write the formatted file to stdout |
64| `max-line-length` | Maximum line length. Used for the `:reflow` command and soft-wrapping |
66### File-type detection and the `file-types` key
68Helix determines which language configuration to use with the `file-types` key
69from the above section. `file-types` is a list of strings or tables, for
70example:
72```toml
73file-types = ["Makefile", "toml", { suffix = ".git/config" }]
74```
76When determining a language configuration to use, Helix searches the file-types
77with the following priorities:
791. Exact match: if the filename of a file is an exact match of a string in a
80 `file-types` list, that language wins. In the example above, `"Makefile"`
81 will match against `Makefile` files.
822. Extension: if there are no exact matches, any `file-types` string that
83 matches the file extension of a given file wins. In the example above, the
84 `"toml"` matches files like `Cargo.toml` or `languages.toml`.
853. Suffix: if there are still no matches, any values in `suffix` tables
86 are checked against the full path of the given file. In the example above,
87 the `{ suffix = ".git/config" }` would match against any `config` files
88 in `.git` directories. Note: `/` is used as the directory separator but is
89 replaced at runtime with the appropriate path separator for the operating
90 system, so this rule would match against `.git\config` files on Windows.
92### Language Server configuration
94The `language-server` field takes the following keys:
96| Key | Description |
97| --- | ----------- |
98| `command` | The name of the language server binary to execute. Binaries must be in `$PATH` |
99| `args` | A list of arguments to pass to the language server binary |
100| `timeout` | The maximum time a request to the language server may take, in seconds. Defaults to `20` |
101| `language-id` | The language name to pass to the language server. Some language servers support multiple languages and use this field to determine which one is being served in a buffer |
102| `environment` | Any environment variables that will be used when starting the language server `{ "KEY1" = "Value1", "KEY2" = "Value2" }` |
104The top-level `config` field is used to configure the LSP initialization options. A `format`
105sub-table within `config` can be used to pass extra formatting options to
106[Document Formatting Requests](https://github.com/microsoft/language-server-protocol/blob/gh-pages/_specifications/specification-3-16.md#document-formatting-request--leftwards_arrow_with_hook).
107For example with typescript:
109```toml
110[[language]]
111name = "typescript"
112auto-format = true
113# pass format options according to https://github.com/typescript-language-server/typescript-language-server#workspacedidchangeconfiguration omitting the "[language].format." prefix.
114config = { format = { "semicolons" = "insert", "insertSpaceBeforeFunctionParenthesis" = true } }
115```
117## Tree-sitter grammar configuration
119The source for a language's tree-sitter grammar is specified in a `[[grammar]]`
120section in `languages.toml`. For example:
122```toml
123[[grammar]]
124name = "mylang"
125source = { git = "https://github.com/example/mylang", rev = "a250c4582510ff34767ec3b7dcdd3c24e8c8aa68" }
126```
128Grammar configuration takes these keys:
130| Key | Description |
131| --- | ----------- |
132| `name` | The name of the tree-sitter grammar |
133| `source` | The method of fetching the grammar - a table with a schema defined below |
135Where `source` is a table with either these keys when using a grammar from a
136git repository:
138| Key | Description |
139| --- | ----------- |
140| `git` | A git remote URL from which the grammar should be cloned |
141| `rev` | The revision (commit hash or tag) which should be fetched |
142| `subpath` | A path within the grammar directory which should be built. Some grammar repositories host multiple grammars (for example `tree-sitter-typescript` and `tree-sitter-ocaml`) in subdirectories. This key is used to point `hx --grammar build` to the correct path for compilation. When omitted, the root of repository is used |
144### Choosing grammars
146You may use a top-level `use-grammars` key to control which grammars are
147fetched and built when using `hx --grammar fetch` and `hx --grammar build`.
149```toml
150# Note: this key must come **before** the [[language]] and [[grammar]] sections
151use-grammars = { only = [ "rust", "c", "cpp" ] }
152# or
153use-grammars = { except = [ "yaml", "json" ] }
154```
156When omitted, all grammars are fetched and built.
158[treesitter-language-injection]: https://tree-sitter.github.io/tree-sitter/syntax-highlighting#language-injection