github-linguist/linguist · error · ArgumentError

invalid type: #{@type}

Error message

invalid type: #{@type}

What it means

Language#initialize converts the `type` attribute to a symbol and validates it against the fixed set returned by get_types: :data, :markup, :programming, :prose (language.rb:305-308). Anything else (or a string that doesn't sym-match one of those four) raises ArgumentError before the language is ever registered. A nil/omitted type passes the check — the error is specifically about a present-but-invalid value. It fires at require time for languages.yml entries and immediately for programmatic Language.new/create calls.

Source

Thrown at lib/linguist/language.rb:270

    #
    # Returns an Array of Languages.
    def self.colors
      @colors ||= all.select(&:color).sort_by { |lang| lang.name.downcase }
    end

    # Internal: Initialize a new Language
    #
    # attributes - A hash of attributes
    def initialize(attributes = {})
      # @name is required
      @name = attributes[:name] || raise(ArgumentError, "missing name")

      @fs_name = attributes[:fs_name]

      # Set type
      @type = attributes[:type] ? attributes[:type].to_sym : nil
      if @type && !get_types.include?(@type)
        raise ArgumentError, "invalid type: #{@type}"
      end

      @color = attributes[:color]

      # Set aliases
      @aliases = [default_alias] + (attributes[:aliases] || [])

      @tm_scope = attributes[:tm_scope] || 'none'
      @ace_mode = attributes[:ace_mode]
      @codemirror_mode = attributes[:codemirror_mode]
      @codemirror_mime_type = attributes[:codemirror_mime_type]
      @wrap = attributes[:wrap] || false

      # Set the language_id
      @language_id = attributes[:language_id]

      # Set extensions or default to [].
      @extensions   = attributes[:extensions]   || []

View on GitHub (pinned to b45dbe9b28)

Solutions

1. Change the type in languages.yml to one of the four valid values: data, markup, programming, or prose.
2. Check for stray characters — quotes, commas, trailing spaces — around the type value in YAML.
3. If you genuinely need a new category, that is a library change (extend get_types) — not a per-entry fix; raise it with maintainers instead.
4. For programmatic use, validate with %i[data markup programming prose].include?(type.to_sym) before construction.

Example fix

# before (lib/linguist/languages.yml)
TOML:
  type: data-format

# after
TOML:
  type: data

VALID_TYPES = %i[data markup programming prose].freeze
unless attributes[:type].nil? || VALID_TYPES.include?(attributes[:type].to_sym)
  raise ArgumentError, "type must be one of #{VALID_TYPES.join(', ')}"
end

def valid_language_type?(t)
  %i[data markup programming prose].include?(t.to_sym)
end

begin
  Linguist::Language.create(attributes)
rescue ArgumentError => e
  raise if e.message !~ /invalid type/
  attributes[:type] = :programming # or prompt the author for the right category
end

When it happens

Trigger: 1) A languages.yml entry with `type: script`, `type: mark-up`, or a trailing character ("programming,") — YAML hands the string over, to_sym produces an unknown symbol. 2) Passing type: :functional in Language.create. 3) Copying an entry from an older/newer version of the file whose allowed type set differs. The message interpolates the symbol, e.g. "invalid type: functional".

Common situations: Contributors guessing at type names ('script', 'markup language', 'data-format'); YAML typos and invisible whitespace in the type value; tooling that generates languages.yml with a type vocabulary from a different schema version.

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

• Extension is missing a '.': #{extension.inspect}
• Duplicate language name: #{language.name}
• Duplicate language name: #{language.fs_name}
• Duplicate alias: #{name}
• read_index is deprecated

AI-assisted analysis of github-linguist/linguist@b45dbe9b28 (2026-08-21). Data as JSON: /api/errors/c58cc6e63fac24bd. Report an issue: GitHub.