puppetlabs/puppet · error · ArgumentError

A block is required

Error message

A block is required

What it means

Puppet::HTTP::ResponseNetHTTP#read_body streams the response body by yielding decoded chunks to a block (it delegates to Net::HTTP's read_body). Calling it without a block cannot stream anything, so it raises ArgumentError; to get the whole body as a String use Response#body instead.

Source

Thrown at lib/puppet/http/response_net_http.rb:24

class Puppet::HTTP::ResponseNetHTTP < Puppet::HTTP::Response
  # Create a response associated with the URL.
  #
  # @param [URI] url
  # @param [Net::HTTPResponse] nethttp The response
  def initialize(url, nethttp)
    super(url, nethttp.code.to_i, nethttp.message)

    @nethttp = nethttp
  end

  # (see Puppet::HTTP::Response#body)
  def body
    @nethttp.body
  end

  # (see Puppet::HTTP::Response#read_body)
  def read_body(&block)
    raise ArgumentError, "A block is required" unless block_given?

    @nethttp.read_body(&block)
  end

  # (see Puppet::HTTP::Response#success?)
  def success?
    @nethttp.is_a?(Net::HTTPSuccess)
  end

  # (see Puppet::HTTP::Response#[])
  def [](name)
    @nethttp[name]
  end

  # (see Puppet::HTTP::Response#each_header)
  def each_header(&block)
    @nethttp.each_header(&block)
  end

View on GitHub (pinned to e227c27540)

Solutions

1. Pass a block: response.read_body { |chunk| out.write(chunk) }.
2. If you want the full body, call response.body instead.
3. When forwarding, guard with block_given? before calling read_body.

Example fix

# before
body = response.read_body

# after (streaming)
response.read_body { |chunk| socket.write(chunk) }

# after (full body)
body = response.body

if block
  response.read_body(&block)
else
  response.body
end

has_block = ->(&b) { !b.nil? }
raise ArgumentError, 'pass a block or use #body' unless has_block { |&blk| blk }

When it happens

Trigger: response.read_body with no block (e.g. assigning its result: body = response.read_body); forwarding &block when block is nil; code ported from Net::HTTP where read_body without a block returns the full body string.

Common situations: Developers used to net/http semantics calling read_body expecting a String return; partial refactors where the consumer callback was removed but the call kept; block passed as &nil via an optional kwarg default.

Related errors

• 'put' requires a string 'body' argument
• 'post' requires a string 'body' argument
• No content type in http response; cannot parse
• Could not download module: %{message}
• No format matches the given format name or mime-type (%{form

AI-assisted analysis of puppetlabs/puppet@e227c27540 (2026-08-21). Data as JSON: /api/errors/3e43ccefceebc604. Report an issue: GitHub.