puppetlabs/puppet · error · Puppet::Network::FormatHandler::FormatError

Could not intern_multiple from %{format}: %{err}

Error message

Could not intern_multiple from %{format}: %{err}

What it means

convert_from_multiple wraps any exception raised while deserializing a list of instances through format.intern_multiple into a FormatError naming the format and the original error. Typical underlying causes: the payload is not a collection (the YAML format raises its own FormatError which then gets wrapped), one element fails parsing, or the class lacks the intern_multiple method (NotImplementedError wrapped).

Source

Thrown at lib/puppet/network/format_support.rb:24

# @api public
module Puppet::Network::FormatSupport
  def self.included(klass)
    klass.extend(ClassMethods)
  end

  module ClassMethods
    def convert_from(format, data)
      get_format(format).intern(self, data)
    rescue => err
      # TRANSLATORS "intern" is a function name and should not be translated
      raise Puppet::Network::FormatHandler::FormatError, _("Could not intern from %{format}: %{err}") % { format: format, err: err }, err.backtrace
    end

    def convert_from_multiple(format, data)
      get_format(format).intern_multiple(self, data)
    rescue => err
      # TRANSLATORS "intern_multiple" is a function name and should not be translated
      raise Puppet::Network::FormatHandler::FormatError, _("Could not intern_multiple from %{format}: %{err}") % { format: format, err: err }, err.backtrace
    end

    def render_multiple(format, instances)
      get_format(format).render_multiple(instances)
    rescue => err
      # TRANSLATORS "render_multiple" is a function name and should not be translated
      raise Puppet::Network::FormatHandler::FormatError, _("Could not render_multiple to %{format}: %{err}") % { format: format, err: err }, err.backtrace
    end

    def default_format
      supported_formats[0]
    end

    def support_format?(name)
      Puppet::Network::FormatHandler.format(name).supported?(self)
    end

    def supported_formats

View on GitHub (pinned to e227c27540)

Solutions

1. Make the payload a collection (YAML sequence / JSON array) of per-instance documents or Hashes.
2. Pre-parse and shape-check: data = Puppet::Util::Yaml.safe_load(text, []); reject unless data.respond_to?(:collect).
3. Fix the producer to serialize arrays when a list is expected.
4. Use convert_from for genuine single documents.

Example fix

# before
Widget.convert_from_multiple(:yaml, File.read('widgets.yaml'))
# widgets.yaml contains '--- 42' → wrapped FormatError

# after — widgets.yaml is a sequence
# ---
# - id: 1
# - id: 2
list = Widget.convert_from_multiple(:yaml, File.read('widgets.yaml'))

data = format == :json ? Puppet::Util::Json.load(text) : Puppet::Util::Yaml.safe_load(text, [])
raise ArgumentError, 'expected a collection of instances' unless data.respond_to?(:collect)
list = Klass.convert_from_multiple(format, text)

begin
  list = Klass.convert_from_multiple(fmt, text)
rescue Puppet::Network::FormatHandler::FormatError => e
  # message embeds the real cause: non-collection, parse error, or missing method
  warn e.message
  list = []
end

When it happens

Trigger: Klass.convert_from_multiple(:yaml, '--- foo') (scalar document); convert_from_multiple(:json, '[{"a":},]') (malformed element); convert_from_multiple(:json, list) on a class without from_json_multiple.

Common situations: List endpoints receiving single-object payloads by mistake; batch report/fact uploads with one corrupt element; producers writing YAML.dump(obj) where the consumer expects YAML.dump([obj]).

Related errors

• Could not intern from %{format}: %{err}
• Serialized YAML did not contain a valid instance of %{klass}
• Serialized YAML did not contain a collection of instances wh
• Serialized YAML did not contain a valid instance of %{klass}
• #{path}: #{detail.message}

AI-assisted analysis of puppetlabs/puppet@e227c27540 (2026-08-21). Data as JSON: /api/errors/47dc9d4b99ecb567. Report an issue: GitHub.