instructure/canvas-lms · error · Translation::UnsupportedLanguageError

UnsupportedLanguageError

Error message

UnsupportedLanguageError

What it means

Raised by handle_cedar_errors in lib/translation.rb:141 when the Cedar translation service reports an UnsupportedLanguageError. The wrapper translates the upstream exception into Canvas's own UnsupportedLanguageError so callers get a consistent error type. It means one of the source or target languages passed to translate_text/translate_html is not supported by the translation backend.

Solutions

1. Check the source/target language codes against the translation service's supported language list before calling translate_text/translate_html
2. Normalize/validate locale codes (format, casing, region) before submission
3. Rescue UnsupportedLanguageError and fall back to a default supported language or skip translation
4. Verify the translation backend configuration/version still supports the requested languages

Example fix

// before
Translation::Service.translate_text(text, from: 'zh_CN', to: 'jp')
// after
raise UnsupportedLanguageError unless SUPPORTED_LANGUAGES.include?(to)
Translation::Service.translate_text(text, from: 'zh-CN', to: 'ja')

raise UnsupportedLanguageError unless SUPPORTED_LANGUAGES.include?(target_locale) && SUPPORTED_LANGUAGES.include?(source_locale)

begin
  translate_text(text, from:, to:)
rescue UnsupportedLanguageError
  fallback_locale_translation(text)
end

When it happens

Trigger: Calling translate_text or translate_html with a locale string the Cedar service does not recognize (malformed code, deprecated locale, or a language outside Cedar's supported set); Cedar returns UnsupportedLanguageError which the case/when block remaps.

Common situations: Hardcoded locale strings that drift from supported language lists; user-submitted target languages not validated against the supported set; locale codes with wrong casing or region suffixes; backend language list changed after an upgrade.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• e.message
• format must be one of #
• SameLanguageTranslationError
• TextTooLongError
• Translation::SameLanguageTranslationError

AI-assisted analysis of instructure/canvas-lms@1c9f0bb801 (2026-09-15). Data as JSON: /api/errors/bf443356686052b1. Report an issue: GitHub.

Appendix: source

Thrown at lib/translation.rb:141

        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
      when /ValidationError/
        raise ValidationError
      else
        raise TranslationError, e.message
      end
    end
  end
end

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