Note

Development on Lexical has halted to focus efforts on Expert, the official Elixir language server. Please refer to Expert's VS Code extension for current status and installation instructions.

Lexical

Lexical is a next-generation language server for the Elixir programming language.

Features

• Context aware code completion
• As-you-type compilation
• Advanced error highlighting
• Code actions
• Code formatting
• Completely isolated build environment
• Syntax highlighting

For all the details on what makes Lexical stand out from other Elixir language servers, see the language server repository.

Using the extension

This extension will automatically download and install the latest Lexical release from Github when starting up. You can disable this behaviour and point the extension to your own build with the lexical.server.releasePathOverride configuration option.

Using with Expert

While this extension was originally built for the Lexical language server, it does not actually have any functionality specific to it outside of automatic server installation.

This means it can also be used with other language servers, such as Expert.

Because vscode-lexical does not yet support passing arguments to the server, a little more work is required to use this extension with Expert. Here is an example configuration:

1. Create a script within your project that starts Expert at the correct location with the --stdio flag. Under your workspace, create the script scripts/start_expert.sh:

   #!/bin/sh
   
   /path/to/my/expert/build --stdio

2. Make the script executable: chmod +x scripts/start_expert.sh
3. Configure vscode-lexical to start the server using this script. In your settings.json:

   {
     "lexical.server.releasePathOverride": "./scripts/start_expert.sh"
   }

Expert should now start instead of Lexical when loading VS Code in your workspace.

Configuration

lexical.server.releasePathOverride

Tells the extension to use a local release of the Lexical language server instead of the automatically installed one. Useful to work on Lexical, or use an older version. This path can point to a directory that holds the lexical start script (assumed to be start_lexical.sh) or any executable launcher script. Relative paths will be interpreted to be relative to the current VS Code workspace.

The path should look something like /home/username/Projects/lexical/_build/dev/package/lexical/bin/start_lexical.sh.

lexical.notifyOnServerAutoUpdate

Controls whether notifications are shown after automatic installs of new Lexcial versions. Defaults to true.

Editor Configuration

The extension provides a language configuration for Elixir which marks do/end and fn/end as brackets. Among other things, this enables colorization of do/end and fn/end with VSCode's editor.bracketPairColorization.enabled setting. While this can be helpful when searching for a do's corresponding end, some users may prefer to use the standard keyword coloring, while still highlighting parenthesis and other brackets. This can be achieved by adding the following to your VSCode configuration.

"editor.bracketPairColorization.enabled": true,
"[elixir]": {
  "editor.language.colorizedBracketPairs": [
    ["{", "}"],
    ["[", "]"],
    ["(", ")"]
  ]
}

Erlang and Elixir version compatibility

Erlang

Auto-installed builds of Lexical are compatible with Elixir and Erlang versions that are newer than the version the build was built with.

Refer to the following table to know which version that is:

Lexical	Erlang
0.2.2	24.3.4.13
>= 0.2.3	24.3.4.12

Refer to the Releases page of Lexical to find out what the latest version is.

These versions are a couple years old, and if you are using newer versions of Elixir and Erlang and Elixir in your projects, perfomrance will likely be better if you built Lexical yourself with a newer version of Elixir and Erlang.

This isn't hard to do: clone the Lexical language server repo, build a release following the instructions in the README and configure the extension to use that local release.

The following table illustrates which versions of Erlang Lexical is compatible with when building yourself.

Erlang	Version range	Notes
24	>= 24.3.4.12	Might run on older versions; this was the lowest that would compile on arm
25	>= 25.0
26	In progress

Elixir

Lexical has much less strict requirements on the version of Elixir. Any supported version of Elixir should work with any build of Lexical, auto-installed or not. The supported versions of Elixir are as follows:

Elixir	Version Range	Notes
1.13	>= 1.13.4
1.14	all
1.15	>= 1.15.3	1.15.0 - 1.15.2 had compiler bugs that prevented lexical from working

Troubleshooting

Lexical outputs logs to two different files:

• lexical.log: Contains logs for the language server node, which handles all the LSP communication, code intelligence, etc.
• project.log: Contains logs for the project node, which handles loading and compiling your project.

Additionally, the Lexical channel in VSCode's Output tab may contain some pertinent information, notably when Lexical fails to start whatsoever (no log files are created).

Frequent issues and questions

Error in output tab: init terminating in do_boot ({load_failed,[logger_simple_h,gen,logger_server,...

This error usually means your version of Erlang is incompatible with your build of Lexical. Please refer to the Erlang compatibility section for more details.

I'm not getting syntax highlighting for HEEx

This extension does not support syntax highlighting for HEEx, either in .heex files or in ~H sigils. HEEx syntax highlighting is provided by the Phoenix Framework extension.

Getting help

If you have questions or need help, please refer to one of the following channels:

• The issues on the vscode-lexical project
• The issues on the lexical project
• The #editor-tooling channel in the Elixir Discord server