Babel LSP — ZedExt

babel-lsp

Language server for Python Babel i18n. Works with .py, Jinja templates, and .po/.pot catalog files.

Features

Diagnostics — 32 checks across source files, PO catalogs, and the whole project
Hover — translation table for any _("msgid") call
Completion — msgid completion in translation calls
Inlay hints — inline translation previews next to _() calls
Code actions — remove fuzzy flags, fill missing translations, rename msgid across all files
Go-to-definition / references / rename — treat msgids as first-class symbols
babel-lsp check — headless CLI linter, same rules as the LSP

Diagnostics

Code	What it catches
`msg/empty-id`	`_("")` — empty string is the catalog header sentinel
`msg/fstring-in-call`	`_(f"…")` — f-string is interpolated before gettext sees it
`msg/format-before-call`	`_("…" % x)` — format applied before gettext
`msg/implicit-concat`	`_("a" "b")` — implicit string concatenation
`msg/non-constant-id`	`_(variable)` — pybabel cannot extract non-literal ids
`msg/unknown-id`	msgid not found in any catalog or template
`msg/missing-in-locale`	msgid translated in some locales but empty in others
`po/header-missing`	missing or incomplete catalog header
`po/duplicate-id`	same msgid appears twice in one file
`po/obsolete`	`#~` entry absent from the `.pot` template
`po/missing-translation`	empty msgstr in a `.po` file
`po/fuzzy`	entry marked `#, fuzzy`
`po/blank`	msgstr is whitespace-only
`po/plural-count`	wrong number of plural forms vs. `nplurals`
`po/same-plurals`	all plural forms are identical
`po/format-mismatch`	printf/brace placeholder missing from translation
`po/extra-variable`	translation has extra placeholders not in source
`po/unchanged`	translation is identical to the source string
`po/newline-count`	`\n` count differs between source and translation
`po/whitespace-edges`	leading/trailing whitespace differs
`po/end-punctuation`	trailing punctuation differs
`po/double-space`	translation has double space not in source
`po/repeated-word`	consecutive repeated word in translation
`po/escape-mismatch`	backslash escape sequences differ
`po/bracket-count`	bracket count differs
`po/accelerator-mismatch`	`&` accelerator marker count differs
`po/xml-tag-mismatch`	XML/HTML tag structure differs
`po/url-changed`	URL from source is absent or path-altered
`po/number-mismatch`	numeric literals differ
`proj/inconsistent-translation`	same msgid translated differently in the same locale
`proj/missing-locale-file`	a locale has `.po` for some domains but not all
`proj/unused-id`	msgid exists in catalog but is never referenced in source

Installation

uv tool install babel-lsp

Or with pip:

pip install babel-lsp

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

Configuration

Place a babel-lsp.toml (or pyproject.toml [tool.babel-lsp] section) at your project root.

# Directories to search for .po/.pot files (auto-detected if absent)
locale_dirs = ["locale"]

# Default locale for features that need one
default_locale = "en"

# Restrict to specific translation domains
# domains = ["messages", "admin"]

# Additional translation functions beyond the built-ins
# (_, gettext, ngettext, pgettext, npgettext, lazy_gettext, …)
extra_keywords = ["my_gettext"]

# Extensions treated as Jinja templates
jinja_extensions = [".html", ".jinja", ".jinja2", ".j2"]

# Locale to show in inlay hints (defaults to first alphabetical locale)
# inlay_hint_locale = "de"

# Path to pybabel (auto-discovered on PATH if absent)
# pybabel_path = "/path/to/pybabel"

[diagnostics]
# Run only these checks (default: all)
# select = ["po/fuzzy", "po/missing-translation"]

# Suppress specific checks
ignore = ["po/unchanged", "po/same-plurals"]

# Override severity per code
[diagnostics.severity]
"po/fuzzy" = "warning"
"proj/unused-id" = "hint"

[unchanged]
# msgids to skip for po/unchanged (e.g. single-word proper nouns)
ignore = ["OK", "PDF"]

CLI

# Check the current project
babel-lsp check

# Check specific paths
babel-lsp check locale/ src/

# Run only selected checks
babel-lsp check --select po/fuzzy,po/missing-translation

# Suppress checks
babel-lsp check --ignore po/unchanged

# Auto-fix what can be fixed (fuzzy flags, missing translations)
babel-lsp check --fix

# Output formats: concise (default), full, json, json-lines, grouped,
#                 github, gitlab, junit, pylint
babel-lsp check --output-format github

# Exit 0 even with findings (useful in pre-commit hooks that only annotate)
babel-lsp check --exit-zero

Editor Setup

Zed

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

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

{
  "languages": {
    "Python": { "language_servers": ["babel-lsp", "..."] }
  }
}

Helix

Merge editors/helix/languages.toml into ~/.config/helix/languages.toml.

Neovim

Requires Neovim 0.11+. Add to your init.lua:

require("lspconfig").babel_lsp.setup {}

Or use the minimal snippet from editors/neovim/babel_lsp.lua.

Other editors

The server speaks standard LSP over stdio:

babel-lsp lsp --stdio

Fixtures

fixtures/ contains one minimal workspace per diagnostic code. Use them to verify diagnostics work or as templates for your own test setups:

babel-lsp check fixtures/po-fuzzy/
babel-lsp check fixtures/po-fuzzy/ --select po/fuzzy