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

ValidationError

Error message

ValidationError

What it means

Raised by handle_cedar_errors in lib/translation.rb:143 when the Cedar translation service returns a ValidationError. The wrapper remaps it to Canvas's ValidationError, signaling the request payload (text, language params, etc.) failed upstream validation.

Solutions

1. Validate input text is non-blank and within size limits before calling the translation service
2. Log e.message from the wrapped error to identify which field failed upstream validation
3. Rescue ValidationError and return a user-friendly message instead of surfacing the raw error
4. Check for recent Cedar/API contract changes if previously valid payloads now fail

Example fix

// before
Translation::Service.translate_html(body, from: nil, to: 'es')
// after
next if body.blank?
Translation::Service.translate_html(body, from: source_locale, to: 'es')

raise ValidationError if text.blank? || text.length > MAX_TRANSLATABLE_LENGTH

begin
  translate_html(html, from:, to:)
rescue ValidationError => e
  logger.warn("translation payload rejected: #{e.message}")
  render json: {error: 'untranslatable content'}, status: :bad_request
end

When it happens

Trigger: translate_text or translate_html called with a payload Cedar rejects: empty/nil text, text exceeding field constraints, invalid options hash, or malformed arguments passed through to the service.

Common situations: Translating empty user-generated content without checking for blank input; passing nil source language; API contract change in Cedar adding new validation rules; oversized request fields.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• An institutional tag category did not pass validation
• app '# ' must be one of: #
• cannot change column: captions - locked by Master Course
• Cannot validate existence for resource type: #
• Caption cannot be empty.

AI-assisted analysis of instructure/canvas-lms@1c9f0bb801 (2026-09-15). Data as JSON: /api/errors/0a635c487c452a89. Report an issue: GitHub.

Appendix: source

Thrown at lib/translation.rb:143

    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

View on GitHub (pinned to 1c9f0bb801)