translations: auto-generate with codex (#37462)

.github/workflows/repo-maintenance.yaml

@@ -9,28 +9,6 @@ env:
   PYTHONPATH: ${{ github.workspace }}
 
 jobs:
-  update_translations:
-    runs-on: ubuntu-latest
-    if: github.repository == 'commaai/openpilot'
-    steps:
-      - uses: actions/checkout@v6
-        with:
-          submodules: true
-      - run: ./tools/op.sh setup
-      - name: Update translations
-        run: python3 selfdrive/ui/update_translations.py --vanish
-      - name: Create Pull Request
-        uses: peter-evans/create-pull-request@c0f553fe549906ede9cf27b5156039d195d2ece0
-        with:
-          author: Vehicle Researcher <user@comma.ai>
-          commit-message: "Update translations"
-          title: "[bot] Update translations"
-          body: "Automatic PR from repo-maintenance -> update_translations"
-          branch: "update-translations"
-          base: "master"
-          delete-branch: true
-          labels: bot
-
   package_updates:
     name: package_updates
     runs-on: ubuntu-latest

selfdrive/ui/tests/test_translations.py

@@ -1,124 +1,106 @@
-import pytest
 import json
-import os
 import re
-import xml.etree.ElementTree as ET
 import string
-import requests
-from openpilot.common.parameterized import parameterized_class
-from openpilot.system.ui.lib.multilang import TRANSLATIONS_DIR, LANGUAGES_FILE
+from pathlib import Path
 
-with open(str(LANGUAGES_FILE)) as f:
-  translation_files = json.load(f)
+import pytest
 
-UNFINISHED_TRANSLATION_TAG = "<translation type=\"unfinished\""  # non-empty translations can be marked unfinished
-LOCATION_TAG = "<location "
-FORMAT_ARG = re.compile("%[0-9]+")
+from openpilot.selfdrive.ui.translations.potools import parse_po
+from openpilot.system.ui.lib.multilang import LANGUAGES_FILE, TRANSLATIONS_DIR
+
+PERCENT_PLACEHOLDER_RE = re.compile(r"%(?:n|\d+)")
+BAD_ENTITY_RE = re.compile(r'@(\w+);')
+LINE_NUMBER_REF_RE = re.compile(r'^#:\s+.+:\d+(?:\s|$)')
+FORMATTER = string.Formatter()
+PO_DIR = Path(str(TRANSLATIONS_DIR))
+
+with LANGUAGES_FILE.open(encoding='utf-8') as f:
+  TRANSLATION_LANGUAGES = json.load(f)
 
 
-@pytest.mark.skip("TODO: update for raylib")
-@parameterized_class(("name", "file"), translation_files.items())
-class TestTranslations:
-  name: str
-  file: str
+def extract_placeholders(text: str) -> list[str]:
+  placeholders = PERCENT_PLACEHOLDER_RE.findall(text)
 
-  @staticmethod
-  def _read_translation_file(path, file):
-    tr_file = os.path.join(path, f"{file}.ts")
-    with open(tr_file) as f:
-      return f.read()
+  try:
+    parsed = list(FORMATTER.parse(text))
+  except ValueError as e:
+    raise AssertionError(f"invalid brace formatting in {text!r}: {e}") from e
 
-  def test_missing_translation_files(self):
-    assert os.path.exists(os.path.join(str(TRANSLATIONS_DIR), f"{self.file}.ts")), \
-                    f"{self.name} has no XML translation file, run selfdrive/ui/update_translations.py"
+  for _, field_name, format_spec, conversion in parsed:
+    if field_name is None:
+      continue
 
-  @pytest.mark.skip("Only test unfinished translations before going to release")
-  def test_unfinished_translations(self):
-    cur_translations = self._read_translation_file(TRANSLATIONS_DIR, self.file)
-    assert UNFINISHED_TRANSLATION_TAG not in cur_translations, \
-                    f"{self.file} ({self.name}) translation file has unfinished translations. Finish translations or mark them as completed in Qt Linguist"
+    token = "{"
+    token += field_name
+    if conversion:
+      token += f"!{conversion}"
+    if format_spec:
+      token += f":{format_spec}"
+    token += "}"
+    placeholders.append(token)
 
-  def test_vanished_translations(self):
-    cur_translations = self._read_translation_file(TRANSLATIONS_DIR, self.file)
-    assert "<translation type=\"vanished\">" not in cur_translations, \
-                    f"{self.file} ({self.name}) translation file has obsolete translations. Run selfdrive/ui/update_translations.py --vanish to remove them"
+  return sorted(placeholders)
 
-  def test_finished_translations(self):
-    """
-      Tests ran on each translation marked "finished"
-      Plural:
-      - that any numerus (plural) translations have all plural forms non-empty
-      - that the correct format specifier is used (%n)
-      Non-plural:
-      - that translation is not empty
-      - that translation format arguments are consistent
-    """
-    tr_xml = ET.parse(os.path.join(TRANSLATIONS_DIR, f"{self.file}.ts"))
 
-    for context in tr_xml.getroot():
-      for message in context.iterfind("message"):
-        translation = message.find("translation")
-        source_text = message.find("source").text
+def load_po_text(po_path: Path) -> str:
+  return po_path.read_text(encoding='utf-8')
 
-        # Do not test unfinished translations
-        if translation.get("type") == "unfinished":
-          continue
 
-        if message.get("numerus") == "yes":
-          numerusform = [t.text for t in translation.findall("numerusform")]
+@pytest.mark.parametrize("language_code", sorted(TRANSLATION_LANGUAGES.values()))
+def test_translation_file_exists(language_code: str):
+  po_path = PO_DIR / f"app_{language_code}.po"
+  assert po_path.exists(), f"missing translation file: {po_path}"
 
-          for nf in numerusform:
-            assert nf is not None, f"Ensure all plural translation forms are completed: {source_text}"
-            assert "%n" in nf, "Ensure numerus argument (%n) exists in translation."
-            assert FORMAT_ARG.search(nf) is None, f"Plural translations must use %n, not %1, %2, etc.: {numerusform}"
 
-        else:
-          assert translation.text is not None, f"Ensure translation is completed: {source_text}"
+@pytest.mark.parametrize("po_path", sorted(PO_DIR.glob("app_*.po")), ids=lambda p: p.name)
+def test_translation_placeholders_are_preserved(po_path: Path):
+  _, entries = parse_po(po_path)
+  language = po_path.stem.removeprefix("app_")
 
-          source_args = FORMAT_ARG.findall(source_text)
-          translation_args = FORMAT_ARG.findall(translation.text)
-          assert sorted(source_args) == sorted(translation_args), \
-                           f"Ensure format arguments are consistent: `{source_text}` vs. `{translation.text}`"
+  for entry in entries:
+    source_placeholders = extract_placeholders(entry.msgid)
 
-  def test_no_locations(self):
-    for line in self._read_translation_file(TRANSLATIONS_DIR, self.file).splitlines():
-      assert not line.strip().startswith(LOCATION_TAG), \
-                       f"Line contains location tag: {line.strip()}, remove all line numbers."
-
-  def test_entities_error(self):
-    cur_translations = self._read_translation_file(TRANSLATIONS_DIR, self.file)
-    matches = re.findall(r'@(\w+);', cur_translations)
-    assert len(matches) == 0, f"The string(s) {matches} were found with '@' instead of '&'"
-
-  def test_bad_language(self):
-    IGNORED_WORDS = {'pédale'}
-
-    match = re.search(r'([a-zA-Z]{2,3})', self.file)
-    assert match, f"{self.name} - could not parse language"
-
-    try:
-      response = requests.get(
-        f"https://raw.githubusercontent.com/LDNOOBW/List-of-Dirty-Naughty-Obscene-and-Otherwise-Bad-Words/master/{match.group(1)}"
+    if entry.is_plural:
+      plural_placeholders = extract_placeholders(entry.msgid_plural)
+      message = (
+        f"{language}: source plural placeholders do not match singular for "
+        + f"{entry.msgid!r}: {source_placeholders} vs {plural_placeholders}"
       )
-      response.raise_for_status()
-    except requests.exceptions.HTTPError as e:
-      if e.response is not None and e.response.status_code == 429:
-        pytest.skip("word list rate limited")
-      raise
+      assert plural_placeholders == source_placeholders, message
 
-    banned_words = {line.strip() for line in response.text.splitlines()}
-
-    for context in ET.parse(os.path.join(TRANSLATIONS_DIR, f"{self.file}.ts")).getroot():
-      for message in context.iterfind("message"):
-        translation = message.find("translation")
-        if translation.get("type") == "unfinished":
+      for idx, msgstr in sorted(entry.msgstr_plural.items()):
+        if not msgstr:
           continue
 
-        translation_text = " ".join([t.text for t in translation.findall("numerusform")]) if message.get("numerus") == "yes" else translation.text
+        translated_placeholders = extract_placeholders(msgstr)
+        message = (
+          f"{language}: plural form {idx} changes placeholders for {entry.msgid!r}: "
+          + f"expected {source_placeholders}, got {translated_placeholders}"
+        )
+        assert translated_placeholders == source_placeholders, message
+    else:
+      if not entry.msgstr:
+        continue
 
-        if not translation_text:
-          continue
+      translated_placeholders = extract_placeholders(entry.msgstr)
+      message = (
+        f"{language}: translation changes placeholders for {entry.msgid!r}: "
+        + f"expected {source_placeholders}, got {translated_placeholders}"
+      )
+      assert translated_placeholders == source_placeholders, message
 
-        words = set(translation_text.translate(str.maketrans('', '', string.punctuation + '%n')).lower().split())
-        bad_words_found = words & (banned_words - IGNORED_WORDS)
-        assert not bad_words_found, f"Bad language found in {self.name}: '{translation_text}'. Bad word(s): {', '.join(bad_words_found)}"
+
+@pytest.mark.parametrize("po_path", sorted(PO_DIR.glob("app_*.po")), ids=lambda p: p.name)
+def test_translation_refs_do_not_include_line_numbers(po_path: Path):
+  for line in load_po_text(po_path).splitlines():
+    assert not LINE_NUMBER_REF_RE.match(line), (
+      f"{po_path.name}: line-number source reference found: {line}"
+    )
+
+
+@pytest.mark.parametrize("po_path", sorted(PO_DIR.glob("app_*.po")), ids=lambda p: p.name)
+def test_translation_entities_are_valid(po_path: Path):
+  matches = BAD_ENTITY_RE.findall(load_po_text(po_path))
+  assert not matches, (
+    f"{po_path.name}: found '@...;' entity typo(s): {', '.join(sorted(set(matches)))}"
+  )

selfdrive/ui/translations/README.md

@@ -1,3 +0,0 @@
-# Multilanguage
-
-[![languages](https://raw.githubusercontent.com/commaai/openpilot/badges/translation_badge.svg)](#)

selfdrive/ui/translations/auto_translate.py

@@ -1,138 +0,0 @@
-#!/usr/bin/env python3
-
-import argparse
-import json
-import os
-import pathlib
-import xml.etree.ElementTree as ET
-from typing import cast
-
-import requests
-
-TRANSLATIONS_DIR = pathlib.Path(__file__).resolve().parent
-TRANSLATIONS_LANGUAGES = TRANSLATIONS_DIR / "languages.json"
-
-OPENAI_MODEL = "gpt-4"
-OPENAI_API_KEY = os.environ.get("OPENAI_API_KEY")
-OPENAI_PROMPT = "You are a professional translator from English to {language} (ISO 639 language code). " + \
-                "The following sentence or word is in the GUI of a software called openpilot, translate it accordingly."
-
-
-def get_language_files(languages: list[str] | None = None) -> dict[str, pathlib.Path]:
-  files = {}
-
-  with open(TRANSLATIONS_LANGUAGES) as fp:
-    language_dict = json.load(fp)
-
-    for filename in language_dict.values():
-      path = TRANSLATIONS_DIR / f"{filename}.ts"
-      language = path.stem
-
-      if languages is None or language in languages:
-        files[language] = path
-
-  return files
-
-
-def translate_phrase(text: str, language: str) -> str:
-  response = requests.post(
-    "https://api.openai.com/v1/chat/completions",
-    json={
-      "model": OPENAI_MODEL,
-      "messages": [
-        {
-          "role": "system",
-          "content": OPENAI_PROMPT.format(language=language),
-        },
-        {
-          "role": "user",
-          "content": text,
-        },
-      ],
-      "temperature": 0.8,
-      "max_tokens": 1024,
-      "top_p": 1,
-    },
-    headers={
-      "Authorization": f"Bearer {OPENAI_API_KEY}",
-      "Content-Type": "application/json",
-    },
-  )
-
-  if 400 <= response.status_code < 600:
-    raise requests.HTTPError(f'Error {response.status_code}: {response.json()}', response=response)
-
-  data = response.json()
-
-  return cast(str, data["choices"][0]["message"]["content"])
-
-
-def translate_file(path: pathlib.Path, language: str, all_: bool) -> None:
-  tree = ET.parse(path)
-
-  root = tree.getroot()
-
-  for context in root.findall("./context"):
-    name = context.find("name")
-    if name is None:
-      raise ValueError("name not found")
-
-    print(f"Context: {name.text}")
-
-    for message in context.findall("./message"):
-      source = message.find("source")
-      translation = message.find("translation")
-
-      if source is None or translation is None:
-        raise ValueError("source or translation not found")
-
-      if not all_ and translation.attrib.get("type") != "unfinished":
-        continue
-
-      llm_translation = translate_phrase(cast(str, source.text), language)
-
-      print(f"Source: {source.text}\n" +
-            f"Current translation: {translation.text}\n" +
-            f"LLM translation: {llm_translation}")
-
-      translation.text = llm_translation
-
-  with path.open("w", encoding="utf-8") as fp:
-    fp.write('<?xml version="1.0" encoding="utf-8"?>\n' +
-             '<!DOCTYPE TS>\n' +
-             ET.tostring(root, encoding="utf-8").decode())
-
-
-def main():
-  arg_parser = argparse.ArgumentParser("Auto translate")
-
-  group = arg_parser.add_mutually_exclusive_group(required=True)
-  group.add_argument("-a", "--all-files", action="store_true", help="Translate all files")
-  group.add_argument("-f", "--file", nargs="+", help="Translate the selected files. (Example: -f fr de)")
-
-  arg_parser.add_argument("-t", "--all-translations", action="store_true", default=False, help="Translate all sections. (Default: only unfinished)")
-
-  args = arg_parser.parse_args()
-
-  if OPENAI_API_KEY is None:
-    print("OpenAI API key is missing. (Hint: use `export OPENAI_API_KEY=YOUR-KEY` before you run the script).\n" +
-          "If you don't have one go to: https://beta.openai.com/account/api-keys.")
-    exit(1)
-
-  files = get_language_files(None if args.all_files else args.file)
-
-  if args.file:
-    missing_files = set(args.file) - set(files)
-    if len(missing_files):
-      print(f"No language files found: {missing_files}")
-      exit(1)
-
-  print(f"Translation mode: {'all' if args.all_translations else 'only unfinished'}. Files: {list(files)}")
-
-  for lang, path in files.items():
-    print(f"Translate {lang} ({path})")
-    translate_file(path, lang, args.all_translations)
-
-
-if __name__ == "__main__":
-  main()

selfdrive/ui/translations/auto_translate.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+DIR="$(cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null && pwd)"
+ROOT="$DIR/../../../"
+
+cd $DIR
+./update_translations.py
+
+command -v codex >/dev/null || {
+  echo "Install codex CLI to continue:"
+  echo "-> https://developers.openai.com/codex/cli"
+  echo
+  exit 1
+}
+
+codex exec --cd "$ROOT" -c 'model_reasoning_effort="low"' --dangerously-bypass-approvals-and-sandbox "$(cat <<EOF
+Update openpilot UI translations in selfdrive/ui/translations.
+- Translate English UI text naturally.
+- Preserve placeholders (%n, %1, {}, {:.1f}), HTML/tags, and plural forms.
+- Edit .po files in place.
+- Print a short summary of changes.
+- All strings should be translated. Don't stop until it's 100%.
+- Be mindful of the layout/style of the UI and length of the original English string.
+EOF
+)"

selfdrive/ui/translations/create_badges.py

@@ -1,108 +0,0 @@
-#!/usr/bin/env python3
-import json
-import os
-import requests
-import xml.etree.ElementTree as ET
-
-from openpilot.common.basedir import BASEDIR
-from openpilot.selfdrive.ui.update_translations import LANGUAGES_FILE, TRANSLATIONS_DIR
-
-BADGE_HEIGHT = 20 + 8
-SHIELDS_URL = "https://img.shields.io/badge"
-
-def parse_po_file(file_path):
-  """
-  Parse a .po file and count total and unfinished translations.
-  Returns: (total_translations, unfinished_translations)
-  """
-  with open(file_path) as f:
-    content = f.read()
-
-  total_translations = 0
-  unfinished_translations = 0
-
-  # Split into entries (separated by blank lines)
-  entries = content.split('\n\n')
-
-  for entry in entries:
-    # Skip header entry (contains Project-Id-Version)
-    if 'Project-Id-Version' in entry:
-      continue
-
-    # Check if this entry has a msgid (translation entry)
-    # After skipping header, any entry with msgid " is a translation
-    # (both msgid "content" and msgid "" for multiline contain msgid ")
-    if 'msgid "' not in entry:
-      continue
-
-    total_translations += 1
-
-    # Check if msgstr is empty (unfinished translation)
-    if 'msgstr ""' in entry:
-      # Check if there are continuation lines with content after msgstr ""
-      lines = entry.split('\n')
-      msgstr_idx = None
-      for i, line in enumerate(lines):
-        if line.strip().startswith('msgstr ""'):
-          msgstr_idx = i
-          break
-
-      if msgstr_idx is not None:
-        # Check if any continuation lines have content
-        has_content = False
-        for line in lines[msgstr_idx + 1:]:
-          stripped = line.strip()
-          # Continuation line with content
-          if stripped.startswith('"') and len(stripped) > 2:
-            has_content = True
-            break
-          # End of entry
-          if stripped.startswith(('msgid', '#')) or not stripped:
-            break
-
-        if not has_content:
-          unfinished_translations += 1
-
-  return (total_translations, unfinished_translations)
-
-if __name__ == "__main__":
-  with open(LANGUAGES_FILE) as f:
-    translation_files = json.load(f)
-
-  badge_svg = []
-  max_badge_width = 0  # keep track of max width to set parent element
-  for idx, (name, file) in enumerate(translation_files.items()):
-    po_file_path = os.path.join(str(TRANSLATIONS_DIR), f"app_{file}.po")
-
-    total_translations, unfinished_translations = parse_po_file(po_file_path)
-
-    percent_finished = int(100 - (unfinished_translations / total_translations * 100.)) if total_translations > 0 else 0
-    color = f"rgb{(94, 188, 0) if percent_finished == 100 else (248, 255, 50) if percent_finished > 90 else (204, 55, 27)}"
-
-    # Download badge
-    badge_label = f"LANGUAGE {name}"
-    badge_message = f"{percent_finished}% complete"
-    if unfinished_translations != 0:
-      badge_message += f" ({unfinished_translations} unfinished)"
-
-    r = requests.get(f"{SHIELDS_URL}/{badge_label}-{badge_message}-{color}", timeout=10)
-    assert r.status_code == 200, "Error downloading badge"
-    content_svg = r.content.decode("utf-8")
-
-    xml = ET.fromstring(content_svg)
-    assert "width" in xml.attrib
-    max_badge_width = max(max_badge_width, int(xml.attrib["width"]))
-
-    # Make tag ids in each badge unique to combine them into one svg
-    for tag in ("r", "s"):
-      content_svg = content_svg.replace(f'id="{tag}"', f'id="{tag}{idx}"')
-      content_svg = content_svg.replace(f'"url(#{tag})"', f'"url(#{tag}{idx})"')
-
-    badge_svg.extend([f'<g transform="translate(0, {idx * BADGE_HEIGHT})">', content_svg, "</g>"])
-
-  badge_svg.insert(0, '<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" ' +
-                   f'height="{len(translation_files) * BADGE_HEIGHT}" width="{max_badge_width}">')
-  badge_svg.append("</svg>")
-
-  with open(os.path.join(BASEDIR, "translation_badge.svg"), "w") as badge_f:
-    badge_f.write("\n".join(badge_svg))

selfdrive/ui/translations/potools.py

@@ -8,7 +8,6 @@ import ast
 import os
 import re
 from dataclasses import dataclass, field
-from datetime import UTC, datetime
 from pathlib import Path
 
 
@@ -165,18 +164,18 @@ def write_po(path: str | Path, header: POEntry | None, entries: list[POEntry]) -
     if header:
       for c in header.comments:
         f.write(c + '\n')
-      if header.flags:
-        f.write('#, ' + ', '.join(header.flags) + '\n')
       f.write(f'msgid {_quote("")}\n')
       f.write(f'msgstr {_quote(header.msgstr)}\n\n')
 
     for entry in entries:
       for c in entry.comments:
         f.write(c + '\n')
-      for ref in entry.source_refs:
+      # Keep file-level context for translators, but drop line numbers to
+      # avoid churning PO diffs on unrelated code edits.
+      source_files = sorted({ref.rsplit(':', 1)[0] for ref in entry.source_refs})
+      for ref in source_files:
         f.write(f'#: {ref}\n')
-      if entry.flags:
-        f.write('#, ' + ', '.join(entry.flags) + '\n')
+      # Runtime loading ignores gettext flags; omit them to reduce noise.
       f.write(f'msgid {_quote(entry.msgid)}\n')
       if entry.is_plural:
         f.write(f'msgid_plural {_quote(entry.msgid_plural)}\n')
@@ -256,31 +255,24 @@ def extract_strings(files: list[str], basedir: str) -> list[POEntry]:
 
 # ──── POT generation ────
 
+def _build_pot_header() -> POEntry:
+  return POEntry(
+    msgstr='Content-Type: text/plain; charset=UTF-8\n',
+  )
+
+
+def _build_po_header(language: str) -> POEntry:
+  plural_forms = PLURAL_FORMS.get(language, 'nplurals=2; plural=(n != 1);')
+  return POEntry(
+    msgstr='Content-Type: text/plain; charset=UTF-8\n' +
+      f'Language: {language}\n' +
+      f'Plural-Forms: {plural_forms}\n',
+  )
+
+
 def generate_pot(entries: list[POEntry], pot_path: str | Path) -> None:
   """Generate a .pot template file from extracted entries."""
-  now = datetime.now(UTC).strftime('%Y-%m-%d %H:%M%z')
-  header = POEntry(
-    comments=[
-      '# SOME DESCRIPTIVE TITLE.',
-      "# Copyright (C) YEAR THE PACKAGE'S COPYRIGHT HOLDER",
-      '# This file is distributed under the same license as the PACKAGE package.',
-      '# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.',
-      '#',
-    ],
-    flags=['fuzzy'],
-    msgstr='Project-Id-Version: PACKAGE VERSION\n' +
-      'Report-Msgid-Bugs-To: \n' +
-      f'POT-Creation-Date: {now}\n' +
-      'PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n' +
-      'Last-Translator: FULL NAME <EMAIL@ADDRESS>\n' +
-      'Language-Team: LANGUAGE <LL@li.org>\n' +
-      'Language: \n' +
-      'MIME-Version: 1.0\n' +
-      'Content-Type: text/plain; charset=UTF-8\n' +
-      'Content-Transfer-Encoding: 8bit\n' +
-      'Plural-Forms: nplurals=INTEGER; plural=EXPRESSION;\n',
-  )
-  write_po(pot_path, header, entries)
+  write_po(pot_path, _build_pot_header(), entries)
 
 
 # ──── PO init (replaces msginit) ────
@@ -305,43 +297,22 @@ def init_po(pot_path: str | Path, po_path: str | Path, language: str) -> None:
   """Create a new .po file from a .pot template (replaces msginit)."""
   _, entries = parse_po(pot_path)
   plural_forms = PLURAL_FORMS.get(language, 'nplurals=2; plural=(n != 1);')
-  now = datetime.now(UTC).strftime('%Y-%m-%d %H:%M%z')
-
-  header = POEntry(
-    comments=[
-      f'# {language} translations for PACKAGE package.',
-      "# Copyright (C) YEAR THE PACKAGE'S COPYRIGHT HOLDER",
-      '# This file is distributed under the same license as the PACKAGE package.',
-      '# Automatically generated.',
-      '#',
-    ],
-    msgstr='Project-Id-Version: PACKAGE VERSION\n' +
-      'Report-Msgid-Bugs-To: \n' +
-      f'POT-Creation-Date: {now}\n' +
-      f'PO-Revision-Date: {now}\n' +
-      'Last-Translator: Automatically generated\n' +
-      'Language-Team: none\n' +
-      f'Language: {language}\n' +
-      'MIME-Version: 1.0\n' +
-      'Content-Type: text/plain; charset=UTF-8\n' +
-      'Content-Transfer-Encoding: 8bit\n' +
-      f'Plural-Forms: {plural_forms}\n',
-  )
 
   nplurals = int(re.search(r'nplurals=(\d+)', plural_forms).group(1))
   for e in entries:
     if e.is_plural:
       e.msgstr_plural = dict.fromkeys(range(nplurals), '')
 
-  write_po(po_path, header, entries)
+  write_po(po_path, _build_po_header(language), entries)
 
 
 # ──── PO merge (replaces msgmerge) ────
 
 def merge_po(po_path: str | Path, pot_path: str | Path) -> None:
   """Update a .po file with entries from a .pot template (replaces msgmerge --update)."""
-  po_header, po_entries = parse_po(po_path)
+  _, po_entries = parse_po(po_path)
   _, pot_entries = parse_po(pot_path)
+  language = Path(po_path).stem.removeprefix("app_")
 
   existing = {e.msgid: e for e in po_entries}
   merged = []
@@ -359,4 +330,4 @@ def merge_po(po_path: str | Path, pot_path: str | Path) -> None:
       merged.append(pot_e)
 
   merged.sort(key=lambda e: e.msgid)
-  write_po(po_path, po_header, merged)
+  write_po(po_path, _build_po_header(language), merged)