Fix load module metadata

README.markdown

@@ -539,6 +539,15 @@ Loads the metadata.json of a target module. Can be used to determine module vers
   notify { $metadata['author']: }
   ~~~
 
+If you do not want to fail the catalog compilation if the metadata file for a module is not present:
+
+  ~~~
+  $metadata = load_module_metadata('mysql', true)
+  if empty($metadata) {
+    notify { "This module does not have a metadata.json file.": }
+  }
+  ~~~
+
 *Type*: rvalue.
 
 #### `lstrip`

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

spec/functions/load_module_metadata_spec.rb

@@ -0,0 +1,29 @@
+require 'spec_helper'
+
+describe 'load_module_metadata' do
+  it { is_expected.not_to eq(nil) }
+  it { is_expected.to run.with_params().and_raise_error(Puppet::ParseError, /wrong number of arguments/i) }
+  it { is_expected.to run.with_params("one", "two", "three").and_raise_error(Puppet::ParseError, /wrong number of arguments/i) }
+
+  it "should json parse the file" do
+     allow(scope).to receive(:function_get_module_path).with(['science']).and_return('/path/to/module/')
+     allow(File).to receive(:exists?).with(/metadata.json/).and_return(true)
+     allow(File).to receive(:read).with(/metadata.json/).and_return('{"name": "spencer-science"}')
+
+     result = subject.call(['science'])
+     expect(result['name']).to eq('spencer-science')
+  end
+
+  it "should fail by default if there is no metadata.json" do
+     allow(scope).to receive(:function_get_module_path).with(['science']).and_return('/path/to/module/')
+     allow(File).to receive(:exists?).with(/metadata.json/).and_return(false)
+     expect {subject.call(['science'])}.to raise_error(Puppet::ParseError)
+  end
+
+  it "should return nil if user allows empty metadata.json" do
+     allow(scope).to receive(:function_get_module_path).with(['science']).and_return('/path/to/module/')
+     allow(File).to receive(:exists?).with(/metadata.json/).and_return(false)
+     result = subject.call(['science', true])
+     expect(result).to eq({})
+  end
+end