instructure/canvas-lms · warning · Translation::SameLanguageTranslationError

Translation::SameLanguageTranslationError

Error message

Translation::SameLanguageTranslationError

What it means

After a Cedar translation completes, Translation#check_same_language compares the detected source language with the requested target language and raises Translation::SameLanguageTranslationError when they are identical — translating text to the language it is already in is rejected as a no-op. Stats are incremented under translation.errors before raising.

Solutions

1. Compare the detected source language to tgt_lang before requesting translation and skip when equal
2. In UIs, disable the translate action when the target language matches the content language
3. Rescue Translation::SameLanguageTranslationError and return the original text untranslated
4. Normalize language codes (region variants) consistently on both sides before comparison

Example fix

# before
translated = Translation.translate_text(text: msg, tgt_lang: 'en', options: opts)
# after
begin
  translated = Translation.translate_text(text: msg, tgt_lang: tgt, options: opts)
rescue Translation::SameLanguageTranslationError
  translated = msg # already in target language
end

# only call when target differs from known/detected source language
next if detected_source_language.to_s == tgt_lang.to_s

begin
  translated = Translation.translate_text(text: text, tgt_lang: tgt_lang, options: opts)
rescue Translation::SameLanguageTranslationError
  translated = text
end

When it happens

Trigger: Calling Translation.translate_text or translate_html where Cedar's detected source_language equals tgt_lang — e.g. translating an English message with tgt_lang:'en', or user-selected target language matching auto-detected content language (including exact string equality like 'pt-BR' vs 'pt-BR'; a variant mismatch such as 'en' vs 'en-US' would not trigger).

Common situations: Users asking to 'translate' a message already in their language; auto-translate features detecting language after the UI already committed a target; seeded/default tgt_lang matching the content locale; case or code-format mismatches that resolve to equal language IDs.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• SameLanguageTranslationError
• TextTooLongError
• UnsupportedLanguageError
• Cedar rate limit exceeded for #
• e.message

AI-assisted analysis of instructure/canvas-lms@1c9f0bb801 (2026-09-15). Data as JSON: /api/errors/80d9c149d69431cb. Report an issue: GitHub.

Appendix: source

Thrown at lib/translation.rb:123

          content: html_string,
          target_language: tgt_lang,
          feature_slug:,
          root_account_uuid:,
          current_user:
        )

        check_same_language(translation_response.source_language, tgt_lang)
        collect_translation_stats(src_lang: translation_response.source_language, tgt_lang:, type: feature_slug)
        translation_response.translation
      end
    end

    private

    def check_same_language(source, target)
      if source == target
        InstStatsd::Statsd.distributed_increment("translation.errors", tags: ["error:same_language"])
        raise Translation::SameLanguageTranslationError
      end
    end

    def collect_translation_stats(src_lang:, tgt_lang:, type:)
      tags = %W[type:#{type} source_language:#{src_lang} dest_language:#{tgt_lang}]
      InstStatsd::Statsd.distributed_increment("translation.invocations", tags:)
    end

    def handle_cedar_errors
      yield
    rescue => e
      case e.class.name
      when /SameLanguageTranslationError/
        raise SameLanguageTranslationError
      when /ContentTooLongError/
        raise TextTooLongError
      when /UnsupportedLanguageError/
        raise UnsupportedLanguageError

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