fastapi-lsp 0.1.6

Language server for FastAPI and Starlette

fastapi-lsp

Language server for FastAPI and Starlette — routes, Depends() graph, url_for, Jinja templates, env/settings. One Rust binary, any LSP-capable editor. Static analysis only.

Features

Diagnostics	param mismatches, shadowed routes, unincluded routers, Depends(fn()), dep cycles, broken url_for, missing templates, undefined env keys
Navigation	test call → handler, Depends() chains both ways, template files, .env lines
Hover	route card: resolved path, router chain, response model, deps, middleware
Completions	route paths, url_for names, template paths, env keys
Symbols	GET /api/books/{book_id} in the symbol picker
Code lenses	test count, dep usage, override count per handler
check CLI	same diagnostics as a linter — fastapi-lsp check .

Installation

uv tool install fastapi-lsp

Or with pip:

pip install fastapi-lsp

Or download a pre-built binary from the releases page.

Editor setup

Neovim

vim.lsp.config('fastapi_lsp', {
  cmd = { 'fastapi-lsp', '--stdio' },
  filetypes = { 'python', 'html', 'htmldjango' },
  root_markers = { 'pyproject.toml', '.git' },
})
vim.lsp.enable('fastapi_lsp')

Helix

# ~/.config/helix/languages.toml
[language-server.fastapi-lsp]
command = "fastapi-lsp"
args = ["--stdio"]

[[language]]
name = "python"
language-servers = ["pyright", "fastapi-lsp"]

[[language]]
name = "html"
language-servers = ["vscode-html-language-server", "fastapi-lsp"]

[[language]]
name = "jinja"
language-servers = ["fastapi-lsp"]

Zed

Install from the Zed extensions panel (Cmd+Shift+X) — search for fastapi-lsp and click Install. It activates automatically for Python, HTML, and Jinja2 files.

To control server order alongside other language servers or pass initialization options, add to ~/.config/zed/settings.json:

{
  "languages": { "Python": { "language_servers": ["fastapi-lsp", "..."] } },
  "lsp": { "fastapi-lsp": { "initialization_options": { "templates": ["app/templates"] } } }
}

Configuration

Zero config for standard projects. Priority: InitializationOptions › fastapi-lsp.toml › [tool.fastapi-lsp] in pyproject.toml.

Option	Default
entrypoint	(auto-detected)	main app file
templates	[]	Jinja template directories
source_roots	[]	extra import resolution roots
env_files	[".env", ".env.example"]	env key definitions
settings_env_files	[".env", ".env.example", ".env.unittest"]	env files checked for BaseSettings coverage
process_env	false	include server process env
process_env_show_values	false	show process-env values in hover
client_fixtures	["client", "async_client"]	pytest HTTP client fixture names
env.ignore	[]	env keys to suppress from diagnostics

Feature toggles — all true by default except test_unknown_paths:

Toggle	Default
diagnostics	true
completion	true
hover	true
navigation	true
code_actions	true
code_lens	true
symbols	true
inlay_hints	true
document_links	true
test_unknown_paths	false

# fastapi-lsp.toml
entrypoint = "app/main.py"
templates = ["app/templates"]

[features]
code_lens = false

[check]
only = []
ignore = ["env/undefined-key"]

CLI

fastapi-lsp lsp [--stdio | --tcp --address 127.0.0.1 --port 9257]
fastapi-lsp check PATH [--only CODES] [--ignore CODES] [--format text|json] [--fix]
fastapi-lsp routes [PATH] [--format text|json]

Development

cargo build
cargo test
uv run --group dev pytest e2e/ -v

License

MIT