Backport fact function

Author: vulpine

lib/puppet/functions/fact.rb

@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+# @summary
+#   Digs into the facts hash using dot-notation
+#
+# Supports the use of dot-notation for referring to structured facts. If a fact requested
+# does not exist, returns Undef.
+#
+# @example Example usage:
+#     fact('osfamily')
+#     fact('os.architecture')
+#
+# @example Array indexing:
+#     fact('mountpoints."/dev".options.1')
+#
+# @example Fact containing a "." in the name:
+#     fact('vmware."VRA.version"')
+#
+Puppet::Functions.create_function(:fact) do
+  # @param fact_name
+  #   The name of the fact to check
+  #
+  # @return
+  #   All information retrieved on the given fact_name
+  dispatch :fact do
+    param 'String', :fact_name
+  end
+
+  def to_dot_syntax(array_path)
+    array_path.map { |string|
+      string.include?('.') ? %("#{string}") : string
+    }.join('.')
+  end
+
+  def fact(fact_name)
+    facts = closure_scope['facts']
+
+    # Transform the dot-notation string into an array of paths to walk. Make
+    # sure to correctly extract double-quoted values containing dots as single
+    # elements in the path.
+    path = fact_name.scan(%r{([^."]+)|(?:")([^"]+)(?:")}).map { |x| x.compact.first }
+
+    walked_path = []
+    path.reduce(facts) do |d, k|
+      return nil if d.nil? || k.nil?
+
+      if d.is_a?(Array)
+        begin
+          result = d[Integer(k)]
+        rescue ArgumentError => e # rubocop:disable Lint/UselessAssignment : Causes errors if assigment is removed.
+          Puppet.warning("fact request for #{fact_name} returning nil: '#{to_dot_syntax(walked_path)}' is an array; cannot index to '#{k}'")
+          result = nil
+        end
+      elsif d.is_a?(Hash)
+        result = d[k]
+      else
+        Puppet.warning("fact request for #{fact_name} returning nil: '#{to_dot_syntax(walked_path)}' is not a collection; cannot walk to '#{k}'")
+        result = nil
+      end
+
+      walked_path << k
+      result
+    end
+  end
+end