What causes "Could not find discussion for language: {lang}" in tiangolo/fastapi?

Create a discussion in the translations category and label it with the matching lang- label.

tiangolo/fastapi · error · RuntimeError

Could not find discussion for language: {lang}

Error message

Could not find discussion for language: {lang}

What it means

Raised by notify_translations.main() at scripts/notify_translations.py:370 when a PR carries a lang-<code> label (e.g. lang-es) but no matching translation discussion exists in the GitHub Discussions translations category. The script builds lang_to_discussion_map from discussions carrying a lang-* label (scripts/notify_translations.py:352-358); a missing entry means there is nowhere to post the review notification, so it aborts rather than silently skip.

Source

Thrown at scripts/notify_translations.py:370

    lang_to_discussion_map: dict[str, AllDiscussionsDiscussionNode] = {}
    for discussion in discussions:
        for edge in discussion.labels.edges:
            label = edge.node.name
            if label.startswith("lang-") and not label == lang_all_label:
                lang = label[5:]
                lang_to_discussion_map[lang] = discussion
    logging.debug(f"Using translations map: {lang_to_discussion_map}")

    # Messages to create or check
    new_translation_message = f"Good news everyone! 😉 There's a new translation PR to be reviewed: #{pr.number} by @{pr.user.login}. 🎉 This requires 2 approvals from native speakers to be merged. 🤓"
    done_translation_message = f"~There's a new translation PR to be reviewed: #{pr.number} by @{pr.user.login}~ Good job! This is done. 🍰☕"

    # Normally only one language, but still
    for lang in langs:
        if lang not in lang_to_discussion_map:
            log_message = f"Could not find discussion for language: {lang}"
            logging.error(log_message)
            raise RuntimeError(log_message)
        discussion = lang_to_discussion_map[lang]
        logging.info(
            f"Found a translation discussion for language: {lang} in discussion: #{discussion.number}"
        )

        already_notified_comment: Comment | None = None
        already_done_comment: Comment | None = None

        logging.info(
            f"Checking current comments in discussion: #{discussion.number} to see if already notified about this PR: #{pr.number}"
        )
        comments = get_graphql_translation_discussion_comments(
            settings=settings, discussion_number=discussion.number
        )
        for comment in comments:
            if new_translation_message in comment.body:
                already_notified_comment = comment
            elif done_translation_message in comment.body:

View on GitHub (pinned to 3e8d1526d8)

Solutions

Create a discussion in the translations category and label it with the matching lang-<code> label.
Confirm the lang-<code> label on the PR exactly matches the label on the discussion (case-sensitive).
If there are more than 100 discussions, add pagination to all_discussions_query (currently capped at first: 100).
Re-run the notify job once the discussion exists.

Defensive patterns

Strategy: try-catch

Try / catch

if lang not in lang_to_discussion_map:
    logging.warning(
        f"No discussion for lang-{lang}; create one and label it, "
        "then re-run the job"
    )
    continue  # or sys.exit(1) if hard-fail is desired

Prevention

Before labeling a PR with a new lang-XX label, create the matching discussion with the same label.
Paginate the discussions query if the category may exceed 100 entries.
Monitor CI for this error when onboarding a new translation language.

When it happens

Trigger: A maintainer labels a PR with a new lang-XX label for a language whose discussion thread has not been created yet, or the discussion exists but lacks the matching lang-XX label. Also if the discussions query returned only the first 100 and the relevant discussion is beyond that page.

Common situations: New translation language added before its discussion category thread exists. Discussion's lang-XX label was renamed or removed. Pagination ceiling: more than 100 discussions in the category (all_discussions_query uses first: 100).

Related errors

AI-assisted analysis of tiangolo/fastapi@3e8d1526d8 (2026-08-11). Data as JSON: /api/errors/646451177ae45751. Report an issue: GitHub.