LSP setup

With cbuildrt>=0.1.2 and xbstrap>=0.26.0, it is now possible to run clangd server inside the build context. This provides autocompletion, hover information, basic refactoring and other features to your text editor of choice.

As the server runs inside a container or within a modified environment, which is a nonstandard configuration, some editor configuration will be required.

Common setup

Using the scripts/managarm-lsp-launcher.sh script in the bootstrap-managarm repository, we can conveniently launch an LSP server in our build environment.

This script discovers what package context you're currently in and runs clangd appropriately. It relies on the compile_commands.json link to figure out what package you're currently in. To create this link, run:

xbstrap -C /path/to/build-dir lsp <package> -- ln -s @THIS_BUILD_DIR@/compile_commands.json

For instance, if <package> is managarm-system, it will place a link in <source dir>/managarm/compile_commands.json, as this is where the xbstrap managarm source is located.

Note on "multi build" sources

Some code, such as the managarm kernel and servers, is built under two distinct configurations from the same source. For these, the above procedure will not be sufficient (which one of the two compile databases do you pick?). As a workaround, we can instruct clangd to conditionally pick a compile database.

In the managarm source directory, drop in a snippet like this one into a file called .clangd at the root:

---
CompileFlags:
  CompilationDatabase: /var/lib/managarm-buildenv/build/pkg-builds/managarm-system
---
If:
  PathMatch: kernel/.*
CompileFlags:
  CompilationDatabase: /var/lib/managarm-buildenv/build/pkg-builds/managarm-kernel

# vim: set ft=yaml :

Your paths might vary, and the LSP launcher relies on a compile database link existing (even if broken), so the above step with ln -s is still necessary.

Editor specific setup

vim (vim-lsp)

To configure vim-lsp, we recommend using a conditional on your working directory based in your Vim startup file:

if executable('xbstrap') && getcwd() =~ '/path/to/bootstrap-managarm/.*'
    au User lsp_setup call lsp#register_server({
        \ 'name': 'xbstrap-lsp-managarm',
        \ 'cmd': {server_info->['/path/to/managarm-lsp-launcher.sh', '/path/to/managarm/build/']},
        \ 'whitelist': ['c', 'cpp', 'objc', 'objcpp'],
        \ })
endif

VSCodium (LLVM clangd)

The LLVM clangd plugin allows you to change the path to clangd. We can use this to launch our wrapper:

{
    "clangd.path": "/path/to/managarm-lsp-launcher.sh",
    "clangd.arguments": ["/path/to/managarm/build/"],
    "clangd.onConfigChanged": "restart"
}

Troubleshooting

In case of trouble, please invoke the script directly like so:

/path/to/managarm-lsp-launcher.sh path/to/build; echo "$?"
  • If the script exits with no output and exit code 1, your build directory is incorrect.
  • If the script exits with no output and exit code 2, there is no compile_commands.json.
  • If you see the clangd banner, but you are seeing issues in the editor, enable the LSP logs in your editor (for instance, g:lsp_log_verbose and g:lsp_log_file with vim-lsp), and check the logs.
  • Export CLANGD_FLAGS="--log=verbose" before running your text editor to increase log verbosity and try again.
  • LLVM 13 changed the meaning of .clangd. It used to be a directory containing the indexer cache, but it was moved to $XDG_CACHE_HOME/clangd. If .clangd is a directory, remove it.
  • If there is no obvious solution, reach out for help.