Let load_module_metadata succeed on empty file

Some modules or module versions don't have a metadata.json file, but we
might still want to use the load_module_metadata function on them. The
lack of a file can still give us important information. For example, it
might tell us that the version of the module installed is "very old"
even if we can't read the version number directly. This patch adds a
parameter to let the user specify if an empty file is acceptable. To
preserve backwards compatibility it does not change the current default
behavior, which is to raise an error if metadata.json does not exist.

1 files changed, 12 insertions, 4 deletions

diff --git a/lib/puppet/parser/functions/load_module_metadata.rb b/lib/puppet/parser/functions/load_module_metadata.rb
index 0664a23..c9b8488 100644
--- a/lib/puppet/parser/functions/load_module_metadata.rb
+++ b/lib/puppet/parser/functions/load_module_metadata.rb
@@ -2,14 +2,22 @@ module Puppet::Parser::Functions
   newfunction(:load_module_metadata, :type => :rvalue, :doc => <<-EOT
   EOT
   ) do |args|
-    raise(Puppet::ParseError, "load_module_metadata(): Wrong number of arguments, expects one") unless args.size == 1
+    raise(Puppet::ParseError, "load_module_metadata(): Wrong number of arguments, expects one or two") unless [1,2].include?(args.size)
     mod = args[0]
+    allow_empty_metadata = args[1]
     module_path = function_get_module_path([mod])
     metadata_json = File.join(module_path, 'metadata.json')
 
-    raise(Puppet::ParseError, "load_module_metadata(): No metadata.json file for module #{mod}") unless File.exists?(metadata_json)
-
-    metadata = PSON.load(File.read(metadata_json))
+    metadata_exists = File.exists?(metadata_json)
+    if metadata_exists
+      metadata = PSON.load(File.read(metadata_json))
+    else
+      if allow_empty_metadata
+        metadata = {}
+      else
+        raise(Puppet::ParseError, "load_module_metadata(): No metadata.json file for module #{mod}")
+      end
+    end
 
     return metadata
   end