LemmyNet/lemmy · error

Failed to construct regex: {e}

Error message

Failed to construct regex: {e}

What it means

Validation error in slur_regex: compiling the slur-filter Regex (built from the local site's slur_filter_regex setting) failed, or the cached build failed. It fires when the admin-configured regex in local_site.slur_filter_regex is invalid, or when try_get_with propagates a concurrent-build failure; the input at fault is the site's slur_filter_regex value.

Source

Thrown at crates/api/api_utils/src/utils.rs:410

}

pub async fn slur_regex(context: &LemmyContext) -> LemmyResult<Regex> {
  static CACHE: CacheLock<Regex> = LazyLock::new(|| {
    Cache::builder()
      .max_capacity(1)
      .time_to_live(CACHE_DURATION_FEDERATION)
      .build()
  });
  Ok(
    Box::pin(CACHE.try_get_with((), async {
      let local_site = SiteView::read_local(&mut context.pool())
        .await
        .ok()
        .map(|s| s.local_site);
      build_and_check_regex(local_site.and_then(|s| s.slur_filter_regex).as_deref())
    }))
    .await
    .map_err(|e| anyhow::anyhow!("Failed to construct regex: {e}"))?,
  )
}

pub async fn get_url_blocklist(context: &LemmyContext) -> LemmyResult<RegexSet> {
  static URL_BLOCKLIST: CacheLock<RegexSet> = LazyLock::new(|| {
    Cache::builder()
      .max_capacity(1)
      .time_to_live(CACHE_DURATION_FEDERATION)
      .build()
  });

  Ok(
    URL_BLOCKLIST
      .try_get_with::<_, LemmyError>((), async {
        let urls = LocalSiteUrlBlocklist::get_all(&mut context.pool()).await?;

        // The urls are already validated on saving, so just escape them.
        // If this regex creation changes it must be synced with

View on GitHub (pinned to 439734dd63)

Solutions

1. Check the local site's slur_filter_regex setting and correct invalid regex syntax.
2. Inspect the wrapped cause `e` to distinguish an invalid regex from a cache/concurrency failure.
3. Clear or wait out the cache TTL after fixing the regex so a good value is rebuilt.

When it happens

Trigger: Thrown at crates/api/api_utils/src/utils.rs:410 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of LemmyNet/lemmy@439734dd63 (2026-09-06). Data as JSON: /api/errors/893bd5e74f54a9f2. Report an issue: GitHub.