rubocop/rubocop · error · RuboCop::ValidationError

configuration for Lint/Syntax cop found in #{smart_loaded_pa

Error message

configuration for Lint/Syntax cop found in #{smart_loaded_path}
It's not possible to disable this cop.

What it means

`Lint/Syntax` is a built-in, always-on cop that reports parser errors; it has no tunable parameters and cannot be disabled. The validator merges your `Lint/Syntax` section with the default and raises `ValidationError` if the result differs in any way — even an `Enabled: false` or an `Exclude` list.

Source

Thrown at lib/rubocop/config_validator.rb:163

      if suggestions.any?
        "Did you mean `#{suggestions.join('`, `')}`?"
      else
        # Department names can contain slashes, e.g. Chef/Correctness, but there's no support for
        # the concept of higher level departments in RuboCop. It's a flat structure. So if the user
        # tries to configure a "top level department", we hint that it's the bottom level
        # departments that should be configured.
        suggestions = departments.select { |department| department.start_with?("#{name}/") }
        "#{name} is not a department. Use `#{suggestions.join('`, `')}`." if suggestions.any?
      end
    end

    def validate_syntax_cop
      syntax_config = @config['Lint/Syntax']
      default_config = ConfigLoader.default_configuration['Lint/Syntax']

      return unless syntax_config && default_config.merge(syntax_config) != default_config

      raise ValidationError,
            "configuration for Lint/Syntax cop found in #{smart_loaded_path}\n" \
            'It\'s not possible to disable this cop.'
    end

    def validate_new_cops_parameter
      validate_all_cops_new_cops_parameter
      validate_department_new_cops_parameters
    end

    def validate_all_cops_new_cops_parameter
      new_cop_parameter = @config.for_all_cops['NewCops']
      return if new_cop_parameter.nil? || NEW_COPS_VALUES.include?(new_cop_parameter)

      message = "invalid #{new_cop_parameter} for `NewCops` found in " \
                "#{smart_loaded_path}\n" \
                "Valid choices are: #{NEW_COPS_VALUES.join(', ')}"

      raise ValidationError, message

View on GitHub (pinned to ea712edf2b)

Solutions

Delete the `Lint/Syntax` section from the config — syntax checking cannot be turned off.
For files that must not be parsed at all, exclude them globally with `AllCops: Exclude` (the files are then never inspected).
If specific files legitimately contain non-Ruby content, give them a non-.rb extension or move them outside the include paths.

Example fix

# before (.rubocop.yml)
Lint/Syntax:
  Enabled: false

# after — drop the section; if files must be skipped entirely:
AllCops:
  Exclude:
    - 'fixtures/invalid.rb'

Defensive patterns

Strategy: validation

Validate before calling

config = YAML.load_file('.rubocop.yml')
if config.key?('Lint/Syntax')
  abort 'Lint/Syntax is not configurable — remove the section; use AllCops: Exclude to skip files'
end

Try / catch

begin
  RuboCop::CLI.new.run([])
rescue RuboCop::ValidationError => e
  raise unless e.message.include?('Lint/Syntax')
  puts 'syntax checking is always on; remove the Lint/Syntax section'
  exit 1
end

Prevention

Never add keys under Lint/Syntax; it is a protected, always-on cop.
To keep broken snippets in-repo, exclude their paths via AllCops: Exclude or use non-Ruby extensions.
Assert in a config linting script that protected sections (Lint/Syntax) are absent.

When it happens

Trigger: Adding `Lint/Syntax: Enabled: false` to silence syntax errors; `Lint/Syntax: Exclude: [vendor/**]` to skip generated or vendored files; any key under `Lint/Syntax` at all besides the identical default.

Common situations: Repos with intentionally invalid Ruby snippets (documentation fixtures, test data) triggering syntax offenses; attempts to exclude generated code from parsing.

Related errors

AI-assisted analysis of rubocop/rubocop@ea712edf2b (2026-08-21). Data as JSON: /api/errors/8f6f983d5885bdf4. Report an issue: GitHub.