Porting functions to the modern Puppet 4.x API

lib/puppet/functions/validate_fact.rb

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+# This is an autogenerated function, ported from the original legacy version.
+# It /should work/ as is, but will not have all the benefits of the modern
+# function API. You should see the function docs to learn how to add function
+# signatures for type safety and to document this function using puppet-strings.
+#
+# https://puppet.com/docs/puppet/latest/custom_functions_ruby.html
+#
+# ---- original file header ----
+
+# ---- original file header ----
+#
+# @summary
+#       Validate that the given fact's value matches any of the
+#    possible expected values given
+#
+#
+#
+#
+Puppet::Functions.create_function(:'validate_fact') do
+  # @param args
+  #   The original array of arguments. Port this to individually managed params
+  #   to get the full benefit of the modern function API.
+  #
+  # @return [Data type]
+  #   Describe what the function returns here
+  #
+  dispatch :default_impl do
+    # Call the method named 'default_impl' when this is matched
+    # Port this to match individual params for better type safety
+    repeated_param 'Any', :args
+  end
+
+
+  def default_impl(*args)
+
+
+    unless args.length == 2
+      raise Puppet::ParseError, "validate_fact: wrong number of arguments (#{args.length}); must be 2"
+    end
+
+    fact = args[0]
+    value = lookupvar(fact)
+
+    expected_values = Array(args[1])
+
+    unless expected_values.member? value
+      raise Puppet::Error, \
+        "validate_fact(#{fact.inspect}): expected #{fact.inspect} to be one of #{expected_values.inspect}, got: '#{value}'"
+    end
+
+
+  end
+end

spec/functions/_validate_fact_spec.rb

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+require 'spec_helper'
+
+describe 'validate_fact' do
+  # without knowing details about the implementation, this is the only test
+  # case that we can autogenerate. You should add more examples below!
+  it { is_expected.not_to eq(nil) }
+
+#################################
+# Below are some example test cases. You may uncomment and modify them to match
+# your needs. Notice that they all expect the base error class of `StandardError`.
+# This is because the autogenerated function uses an untyped array for parameters
+# and relies on your implementation to do the validation. As you convert your
+# function to proper dispatches and typed signatures, you should change the
+# expected error of the argument validation examples to `ArgumentError`.
+#
+# Other error types you might encounter include
+#
+# * StandardError
+# * ArgumentError
+# * Puppet::ParseError
+#
+# Read more about writing function unit tests at https://rspec-puppet.com/documentation/functions/
+#
+#   it 'raises an error if called with no argument' do
+#     is_expected.to run.with_params.and_raise_error(StandardError)
+#   end
+#
+#   it 'raises an error if there is more than 1 arguments' do
+#     is_expected.to run.with_params({ 'foo' => 1 }, 'bar' => 2).and_raise_error(StandardError)
+#   end
+#
+#   it 'raises an error if argument is not the proper type' do
+#     is_expected.to run.with_params('foo').and_raise_error(StandardError)
+#   end
+#
+#   it 'returns the proper output' do
+#     is_expected.to run.with_params(123).and_return('the expected output')
+#   end
+#################################
+
+end