# `vis-lspc`

A language server protocol client for the [`vis` editor](https://github.com/martanne/vis).

## What's working

`vis-lspc` currently supports:
* `textDocument/completion`
* `textDocument/declaration`
* `textDocument/definition`
* `textDocument/references`
* `textDocument/typeDefinition`
* `textDocument/implementation`
* `textDocument/hover`
* `textDocument/rename`
* `textDocument/formatting`
* `textDocument/documentSymbol` *Experimental*
* `Diagnostics`

## What's not working

Everything else.

To my knowledge there is currently no good way to detect file changes via the Lua API.
But this is essential to support [Text Synchronization](https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textSynchronization) which is required by the
LSP protocol.

A dirty workaround we currently use is to send the whole file content in a `textDocument/didChange`
method call before calling any other method.
If someone can come up with an idea how to solve this I would appreciate contributions.

Communicating with language-servers via other channels than stdin/stdout.

Currently, only a handful of language servers are configured by default.
Their configuration can be found in [`supported_servers.lua`](https://gitlab.com/muhq/vis-lspc/-/blob/main/supported-servers.lua).

## Requirements

* `vis` must offer the `communicate` Lua API
  * The API included in `vis` >= 0.9 is supported on the main branch
  * For legacy support using the [first API draft patches](https://github.com/martanne/vis/pull/675) use the v0.2.x branch
* The language server you want to use. [Microsoft's list of implementations](https://microsoft.github.io/language-server-protocol/implementors/servers/)
* Optional: the JSON implementation of your choice
	* must provide `encode` and `decode` methods
	* `vis-lspc` tries to find a suitable JSON implementation using those candidates:
		* `json`
		* `cjson`
		* `dkjson`
		* bundled fallback (no utf8 support)

## Installation

1. Clone this repository into your `vis` plugins directory
2. Load the plugin in your `visrc.lua` with `require('plugins/vis-lspc')`

Alternatively, a plugin manager like [vis-plug](https://github.com/erf/vis-plug) can be used to install `vis-lspc`.

## Usage

`vis-lspc` provides some default key bindings:

### Default Bindings

	Normal mode:
	<F2> - start a language server for win.syntax
	<F3> - open win.file with a running language server
	<C-]> | <gd> - jump to the definition of the symbol under the main cursor
	<gD> - jump to declaration
	<gd> - jump to definition
	<gi> - jump to implementation
	<gr> - show references
	< D> - jump to type definition
	<C-t> - go back in the jump history
	< e> - show diagnostics of current line
	< n> - jump to the next available diagnostic
	< N> - jump to the previous available diagnostic
	<K> - hover over current position
	Normal and Insert mode:
	<C- > - get completions
	< o> - open the symbol navigation window

#### Navigation Window

	Normal mode:
	<p> - scroll to the selected symbol
	<Enter> - jump to the selected symbol (switch to the code window)
	<q> - close the navigaion window

### Available commands

	# language-server management:
	lspc-start-server [syntax] - start a language server for syntax or win.syntax
	lspc-stop-server [syntax] - stop the language server for syntax or win.syntax

	# file registration:
	lspc-open - register the file in the current window
	lspc-close - unregister the file in the current window

	# navigation commands (they all operate on the symbol under the main cursor):
	lspc-completion - syntax completion
	lspc-references [e | vsplit | hsplit] - select and open a reference
	lspc-declaration [e | vsplit | hsplit] - select and open a declaration
	lspc-definition [e | vsplit | hsplit] - open the definition
	lspc-typeDeclaration [e | vsplit | hsplit] - select and open a type declaration
	lspc-implementation [e | vsplit | hsplit] - I actually have no idea what this does

	lspc-back - navigate back in the goto history

	# workspace edits
	lspc-rename <new name> - rename the identifier under the cursor to <new name>
	lspc-format - format the file in the current window

	# development support
	lspc-hover - hover over the current line
	lspc-show-diagnostics - show the available diagnostics of the current line
	lspc-next-diagnostic - jump to the next available diagnostic
	lspc-prev-diagnostic - jump to the previous available diagnostic

	# navigation windows
	lspc-navigate-symbols - navigate a file by its symbols in a seperate window
	lspc-navwin-scroll - scroll to the selected symbol
	lspc-navwin-jump - jump to the selected symbol
	lspc-navwin-close - close the navigation window

### Available configuration options

The module table returned by `require('plugins/vis-lspc')` can be used to configure
some aspects of `vis-lspc`.

Available options are:

* `name = 'vis-lspc'` - the name `vis-lspc` introduces itself to a language server
* `logging = false` - enable logging only useful for debugging `vis-lspc`
* `log_file = nil` - nil, filename, or function returning a filename
  * If `log_file` is `nil` `vis-lspc` will create a new file in `$XDG_DATA_HOME/vis-lspc`
* `autostart = true` - try to start a language server in WIN_OPEN
* `menu_cmd = 'fzf' or 'vis-menu'` - program to prompt for user choices
* `confirm_cmd = 'vis-menu'` - program to prompt for user confirmation
* `autoconfirm_edits = false` - apply workspaceEdits without user confirmation
* `ls_map` - a table mapping `vis` syntax names to language server configurations
* `highlight_diagnostics = 'line'` - highlight the `range` or `line`number of available diagnostics
* `diagnostic_style_id = nil` - vis style id used to highlight diagnostics, win.STYLE_LEXER_MAX is used by default
* `diagnostic_styles = { error = 'back:red', warning = 'back:yellow', information = 'back:yellow', hint = 'back:yellow', }` - styles used to highlight different diagnostics
* `workspace_edit_remember_cursor = true` - restore the primary cursor position after a workspaceEdit
* `message_level = 3` - the level of shown messages retrieved via `window/showMessage` notifications
* `show_message = 'message'` - how to present information. `'message'`: use `vis:message`; `'open'`: use a new window supporting syntax highlighting.
* `universal_root_globs = {}` - Globs to consider as workspace root for any language server (e.g. `*.git` or `*.hg`).
* `fallback_dirname_as_root = false` - If set to true a file's directory is used as workspace root if no explicit root was found.
* `navwin_symbols_format = '%s[%.1s] %s\n'` - The format string used to display a symbol in the symbol navigation window.
* `navwin_layout = 'vr'` - Layout where the navigation window will be placed (`v[r|l]|h[t|b]`: vertical right or left; horizontal top or bottom).

#### Configure your own Language Server

If `vis-lspc` has no language server configuration for your desired language or server
you have to create a language server configuration and insert it into the `ls_map`
table.
Please have a look at #2 and share your configuration with everyone else.

A language server configuration is a Lua table containing at least a `name` field
which is used to manage the language server and a `cmd` field which is used to
start the language server.

**Note:** the language server must communicate with `vis-lspc` via stdio.
Your language server probably supports stdio but maybe requires a [special
command line flag](https://microsoft.github.io/language-server-protocol/specifications/specification-current/#implementationConsiderations).

Additional fields are:

* `settings` - a table of arbitrary possibly nested data. It is sent in a `workspace/didChangeConfiguration` to the language server after initialization. It is also used to lookup configuration for the `workspace/configuratio` method call.
* `init_options` - table of arbitrary possibly nested data. It will be sent to the server as `initializationOptions` in the parameters of the `initialize` method call.
* `formatting_options` - table of configuration data as found in [the LSP specification](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_formatting). `tabSize` and `insertSpaces` are required.

**Example:** The language server configuration entry in the `ls_map` for `lua-language-server`

```lua
ls_map.lua = {
  name = 'lua-language-server',
  cmd = 'lua-language-server',
  settings = {
    Lua = {diagnostics = {globals = {'vis'}}, telemetry = {enable = false}},
  },
  formatting_options = {tabSize = 2, insertSpaces = true},
},
```

Language servers configured in `vis-lspc` can be found in `supported_servers.lua`.

#### Language Server Settings

Language servers can be configured with different mechanisms, all merged together to form the *effective* settings for a language server instance.
There are three kinds of settings:

1. *Global settings* specified by the user in its `vis` configuration in a language server configuration's `settings` member.
2. *Project local* settings stored in a `.vis-lspc-settings.json` file along your regular project files.
3. Settings stored by `vis-lspc` in the `settings.json` file.
   The *client local* user settings are stored for each language server and each file path.
   Settings for a more specific file path override settings defined for a parent directory.

The *project* and *client local* settings are indexed by the name of the language server.

All relevant settings are merged to form the *effective* settings passed to the language server.
More specific settings take precedence before more general ones.

### Workspace Detection

During server initialization an URI to the root of the workspace (a folder opened by the editor) can be passed to the server.
Workspaces are used to implement certain project wide [features](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#workspace_symbol).

Since vis has no sense of folders and I think it is the job of each individual language server to detect the root of language idiomatic projects, workspace root detection is only activated for certain language servers by default.

If you want to use some universal criteria to detect project roots, like always using a file's directory or considering all source-control repositories as projects you can use the configuration options `universal_root_globs` and `fallback_dirname_as_root`.

Additionally, you can configure globs to detect a project's root for each language server using the `roots` member in its `ls_map` table entry.

For example, `roots = {'compile_commands.json', '.clangd'}` is used to detect the project root for clangd.

### Events

vis-lspc extends vis' event system with its own set of events:

* `lspc.event.LS_INITIALIZED` - emitted after sending the `initialized` notification
* `lspc.event.LS_DID_OPEN` - emitted after sending the `textDocument/didOpen` notification

All events receive the language server as first argument.

### Extensibility

The returned module table also includes functions you can use in your own `vis`
configuration.

#### `lspc.lspc_open`

Navigate between or in files, while remembering the current position in a runtime history.

```lua
lspc_open(win, path, line, col, cmd)
```

  - `win` - a window in which to open the file
  - `path` - the path to the file to open
  - `line` - the line to open. (`nil` for no position within the file).
  - `col` - same as `line`, but for the column.
  - `cmd` - `vis` command to open the file. (`e` or `o`, see `vis` commands)

#### `lspc.get_running_ls`

Get a running language server table.

```lua
get_running_ls(win, explicit_syntax)
```

  - `win` - a window in which the language server is running
  - `explicit_syntax` - syntax of the language server if it differs from `win.syntax`

## License

All code except otherwise noted is licensed under the term of GPL-3.
See the LICENSE file for more details.
Our fallback JSON implementation in `json.lua` is NOT licensed under GPL-3.
It is taken from [here](https://gist.github.com/tylerneylon/59f4bcf316be525b30ab)
and is put into public domain by [Tyler Neylon](https://github.com/tylerneylon).