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require_relative '../../puppet'
require_relative '../../puppet/util/warnings'
class Puppet::Util::Feature
include Puppet::Util::Warnings
attr_reader :path
# Create a new feature test. You have to pass the feature name, and it must be
# unique. You can pass a block to determine if the feature is present:
#
# Puppet.features.add(:myfeature) do
# # return true or false if feature is available
# # return nil if feature may become available later
# end
#
# The block should return true if the feature is available, false if it is
# not, or nil if the state is unknown. True and false values will be cached. A
# nil value will not be cached, and should be used if the feature may become
# true in the future.
#
# Features are often used to detect if a ruby library is installed. To support
# that common case, you can pass one or more ruby libraries, and the feature
# will be true if all of the libraries load successfully:
#
# Puppet.features.add(:myfeature, libs: 'mylib')
# Puppet.features.add(:myfeature, libs: ['mylib', 'myotherlib'])
#
# If the ruby library is not installed, then the failure is not cached, as
# it's assumed puppet may install the gem during catalog application.
#
# If a feature is defined using `:libs` and a block, then the block is
# used and the `:libs` are ignored.
#
# Puppet evaluates the feature test when the `Puppet.features.myfeature?`
# method is called. If the feature test was defined using a block and the
# block returns nil, then the feature test will be re-evaluated the next time
# `Puppet.features.myfeature?` is called.
#
# @param [Symbol] name The unique feature name
# @param [Hash<Symbol,Array<String>>] options The libraries to load
def add(name, options = {}, &block)
method = name.to_s + "?"
@results.delete(name)
meta_def(method) do
# we return a cached result if:
# * if we've tested this feature before
# AND
# * the result was true/false
# OR
# * we're configured to never retry
if @results.has_key?(name) &&
(!@results[name].nil? || !Puppet[:always_retry_plugins])
!!@results[name]
else
@results[name] = test(name, options, &block)
!!@results[name]
end
end
end
# Create a new feature collection.
def initialize(path)
@path = path
@results = {}
@loader = Puppet::Util::Autoload.new(self, @path)
end
def load
@loader.loadall(Puppet.lookup(:current_environment))
end
def method_missing(method, *args)
return super unless method.to_s =~ /\?$/
feature = method.to_s.sub(/\?$/, '')
@loader.load(feature, Puppet.lookup(:current_environment))
respond_to?(method) && self.send(method)
end
# Actually test whether the feature is present. We only want to test when
# someone asks for the feature, so we don't unnecessarily load
# files.
def test(name, options, &block)
if block_given?
begin
result = yield
rescue StandardError,ScriptError => detail
warn _("Failed to load feature test for %{name}: %{detail}") % { name: name, detail: detail }
result = nil
end
@results[name] = result
result
else
libs = options[:libs]
if libs
libs = [libs] unless libs.is_a?(Array)
libs.all? { |lib| load_library(lib, name) } ? true : nil
else
true
end
end
end
private
def load_library(lib, name)
raise ArgumentError, _("Libraries must be passed as strings not %{klass}") % { klass: lib.class } unless lib.is_a?(String)
@rubygems ||= Puppet::Util::RubyGems::Source.new
@rubygems.clear_paths
begin
require lib
true
rescue LoadError
# Expected case. Required library insn't installed.
debug_once(_("Could not find library '%{lib}' required to enable feature '%{name}'") %
{lib: lib, name: name})
false
rescue StandardError, ScriptError => detail
debug_once(_("Exception occurred while loading library '%{lib}' required to enable feature '%{name}': %{detail}") %
{lib: lib, name: name, detail: detail})
false
end
end
end
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