puppetlabs/puppet · error · Puppet::DevError

No ability to determine if %{name} exists

Error message

No ability to determine if %{name} exists

What it means

For the ensure property, retrieve decides :present vs :absent by asking resource.provider for exists?, falling back to the resource type itself. When neither side responds to exists?, Puppet::DevError 'No ability to determine if <type> exists' is raised the moment the resource is evaluated. It always indicates a custom type/provider gap: core types implement exists? somewhere in their provider stack.

Source

Thrown at lib/puppet/property/ensure.rb:88

  # `:exists`), and secondly the resource. A a value of `:present` or `:absent` is returned
  # depending on if the managed entity exists or not.
  #
  # @return [Symbol] a value of `:present` or `:absent` depending on if it exists or not
  # @raise [Puppet::DevError] if neither the provider nor the resource responds to `:exists`
  #
  def retrieve
    # XXX This is a problem -- whether the object exists or not often
    # depends on the results of other properties, yet we're the first property
    # to get checked, which means that those other properties do not have
    # @is values set.  This seems to be the source of quite a few bugs,
    # although they're mostly logging bugs, not functional ones.
    prov = @resource.provider
    if prov && prov.respond_to?(:exists?)
      result = prov.exists?
    elsif @resource.respond_to?(:exists?)
      result = @resource.exists?
    else
      raise Puppet::DevError, _("No ability to determine if %{name} exists") % { name: @resource.class.name }
    end
    if result
      :present
    else
      :absent
    end
  end

  # If they're talking about the thing at all, they generally want to
  # say it should exist.
  # defaultto :present
  defaultto do
    if @resource.managed?
      :present
    else
      nil
    end
  end

View on GitHub (pinned to e227c27540)

Solutions

1. Implement def exists? as an instance method in the provider class.
2. Verify a provider is actually suitable (confine, commands, defaultfor) so the resource gets one.
3. If the type can decide existence without a provider, define exists? on the resource type itself.

Example fix

# before (provider)
Puppet::Type.type(:mything).provide(:ruby) do
  # no exists? -> ensure raises Puppet::DevError on retrieve
end

# after
Puppet::Type.type(:mything).provide(:ruby) do
  def exists?
    File.exist?("/etc/mything/#{resource[:name]}")
  end
end

prov = resource.provider
unless prov.nil? || prov.respond_to?(:exists?) || resource.respond_to?(:exists?)
  raise Puppet::Error, "#{resource.class.name} has no provider that implements exists?"
end

def can_determine_existence?(resource)
  (resource.provider && resource.provider.respond_to?(:exists?)) || resource.respond_to?(:exists?)
end

begin
  resource.property(:ensure).retrieve
rescue Puppet::DevError => e
  raise unless e.message =~ /No ability to determine/
  Puppet.err("#{resource}: no provider exists?; skipping")
end

When it happens

Trigger: A custom type with no suitable provider on the platform; a provider that implements exists? as a class method (def self.exists?) instead of an instance method; a provider whose exists? was lost in a refactor.

Common situations: Custom types under development; providers whose confine rules exclude the current platform so no provider is selected; types intended for prefetch-only flows that never define existence.

Related errors

• Provider %{provider} must have features '%{needed_feature}'
• Could not convert change %{name} to string: %{detail}
• To support listing resources of this type the '%{provider}'
• Unable to verify the SSL certificate at %{uri}
• Unable to connect to the server at %{uri}. Detail: %{detail}

AI-assisted analysis of puppetlabs/puppet@e227c27540 (2026-08-21). Data as JSON: /api/errors/8d049e6823153ad8. Report an issue: GitHub.