puppetlabs/puppet · error · ArgumentError

Cannot have fields named %{name}

Error message

Cannot have fields named %{name}

What it means

Puppet::Util::FileParsing records turn each parsed line into a hash keyed by field name, and three keys — :record_type, :target, and :on_disk — are reserved for Puppet's own bookkeeping (they carry the record kind, the target file, and the on-disk flag). FileRecord#fields= rejects those names with ArgumentError at provider-definition time, before any file is read.

Source

Thrown at lib/puppet/util/fileparsing.rb:45

# the text line again.

module Puppet::Util::FileParsing
  include Puppet::Util
  attr_writer :line_separator, :trailing_separator

  class FileRecord
    include Puppet::Util
    attr_accessor :absent, :joiner, :rts, :separator, :rollup, :name, :match, :block_eval

    attr_reader :fields, :optional, :type

    INVALID_FIELDS = [:record_type, :target, :on_disk]

    # Customize this so we can do a bit of validation.
    def fields=(fields)
      @fields = fields.collect do |field|
        r = field.intern
        raise ArgumentError, _("Cannot have fields named %{name}") % { name: r } if INVALID_FIELDS.include?(r)

        r
      end
    end

    def initialize(type,
                   absent: nil,
                   block_eval: nil,
                   fields: nil,
                   joiner: nil,
                   match: nil,
                   optional: nil,
                   post_parse: nil,
                   pre_gen: nil,
                   rollup: nil,
                   rts: nil,
                   separator: nil,
                   to_line: nil,

View on GitHub (pinned to e227c27540)

Solutions

1. Rename the field (e.g. :target to :destination, :record_type to :kind) and update any match/process/to_line hooks accordingly
2. If the value genuinely duplicates Puppet's metadata, drop the field and read details[:target] or details[:record_type] instead

Example fix

# before
record_line :route, fields: %i[destination gateway target], separator: /\s+/
# => ArgumentError: Cannot have fields named target

# after
record_line :route, fields: %i[destination gateway interface], separator: /\s+/

INVALID = %i[record_type target on_disk]
fields = wanted_fields - INVALID
record_line :myline, fields: fields

When it happens

Trigger: Writing record_line :myline, fields: %i[name target] (or :record_type / :on_disk) in a custom provider based on Puppet::Util::FileParsing or Puppet::Provider::ParsedFile — the pattern used by Puppet's own host, port, and mounting providers.

Common situations: Authoring a new parsed-file provider and naturally wanting a field literally named 'target' or 'record_type'; porting an old provider to a newer Puppet that added or extended the reserved list.

Related errors

• Invalid record type %{record_type}
• Field '%{field}' is required
• Process record type %{record_name} returned non-hash
• No record types defined; cannot parse lines
• Somehow got invalid line type %{record_type}

AI-assisted analysis of puppetlabs/puppet@e227c27540 (2026-08-21). Data as JSON: /api/errors/6e56c55884f3d205. Report an issue: GitHub.