SeleniumHQ/selenium · error · ArgumentError

Unknown pattern type: #{pattern_type}

Error message

Unknown pattern type: #{pattern_type}

What it means

UrlPattern.format_pattern converts caller-supplied URL filters into the BiDi network interception wire shape. It only knows two strategies: :string (string match) and :url (parsed URL pattern). Any other pattern_type symbol raises ArgumentError. This is an internal helper used when building network intercept arguments.

Source

Thrown at rb/lib/selenium/webdriver/bidi/network/url_pattern.rb:39

module Selenium
  module WebDriver
    class BiDi
      #
      # @api private
      #

      module UrlPattern
        module_function

        def format_pattern(url_patterns, pattern_type)
          case pattern_type
          when :string
            to_url_string_pattern(url_patterns)
          when :url
            to_url_pattern(url_patterns)
          else
            raise ArgumentError, "Unknown pattern type: #{pattern_type}"
          end
        end

        def to_url_pattern(*url_patterns)
          url_patterns.flatten.map do |url_pattern|
            uri = URI.parse(url_pattern)

            {
              type: 'pattern',
              protocol: uri.scheme || '',
              hostname: uri.host || '',
              port: uri.port.to_s,
              pathname: uri.path || '',
              search: uri.query || ''
            }
          end
        end

View on GitHub (pinned to aa36b38e69)

Solutions

1. Pass pattern_type: :string for substring/string match or pattern_type: :url for a parsed URL pattern.
2. If you need a new kind, extend UrlPattern with a matching to_*_pattern method rather than passing an unknown type.
3. Search your codebase for callers of format_pattern / add_intercept to find the bad type.

Example fix

// before
UrlPattern.format_pattern(patterns, :regex)
// after
UrlPattern.format_pattern(patterns, :string)

VALID_PATTERN_TYPES = %i[string url].freeze

raise ArgumentError, 'bad pattern_type' unless VALID_PATTERN_TYPES.include?(pattern_type)
UrlPattern.format_pattern(url_patterns, pattern_type)

def valid_pattern_type?(t)
  %i[string url].include?(t)
end

begin
  UrlPattern.format_pattern(patterns, type)
rescue ArgumentError => e
  raise unless e.message =~ /Unknown pattern type/
  type = :string
  retry
end

When it happens

Trigger: Calling the internal format_pattern / network intercept API with a pattern_type other than :string or :url. Most often reached through a library bug or monkey-patch that passes :regex, :glob, :wildcard, or nil.

Common situations: Library internal misuse, downstream gem extending network interception with a custom type without patching format_pattern, typo in a fork.

Related errors

• Pattern must be an instance of UrlPattern. Received: '${patt
• Pattern must be an instance of UrlPattern. Received:'${patte
• Pattern must be an instance of String. Received:'${pattern}'
• Params must be an instance of AddInterceptParameters. Receiv
• Params must be an instance of ContinueRequestParameters. Rec

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/41d5e2e562061a17. Report an issue: GitHub.