Add support for YAML templates (#133)

lib/moonshot/json_stack_template.rb

@@ -0,0 +1,17 @@
+require 'json'
+require_relative 'stack_template'
+
+module Moonshot
+  # Handles JSON formatted AWS template files.
+  class JsonStackTemplate < StackTemplate
+    def body
+      template_body.to_json
+    end
+
+    private
+
+    def template_body
+      @template_body ||= JSON.parse(File.read(@filename))
+    end
+  end
+end

lib/moonshot/stack.rb

@@ -1,7 +1,8 @@
 require_relative 'creds_helper'
 require_relative 'doctor_helper'
 
-require_relative 'stack_template'
+require_relative 'yaml_stack_template'
+require_relative 'json_stack_template'
 require_relative 'stack_parameter_printer'
 require_relative 'stack_output_printer'
 require_relative 'stack_asg_printer'
@@ -154,12 +155,20 @@ def default_values
     end
 
     def template
-      @template ||= StackTemplate.new(template_file, log: @log)
+      @template ||= load_template_file
     end
 
     # @return [String] the path to the template file.
     def template_file
-      File.join(Dir.pwd, 'cloud_formation', "#{@app_name}.json")
+      json = json_template_path
+      yaml = yaml_template_path
+
+      @template_file ||= Dir[json].first || Dir[yaml].first
+
+      raise 'CloudFormation template not found at'\
+            "#{json} or #{yaml}!" unless @template_file
+
+      @template_file
     end
 
     # @return [String] the path to the parameters file.
@@ -195,6 +204,33 @@ def load_parameters_file
       end
     end
 
+    def json_template_path
+      "#{raw_template_file_name}.json"
+    end
+
+    def yaml_template_path
+      "#{raw_template_file_name}.yml"
+    end
+
+    # @return [String] the path to the template file without extension.
+    def raw_template_file_name
+      @raw_template_file_name ||= File.join(Dir.pwd, 'cloud_formation', @app_name)
+    end
+
+    def load_template_file
+      json_template = JsonStackTemplate.new(json_template_path, log: @log)
+      yaml_template = YamlStackTemplate.new(yaml_template_path, log: @log)
+      case
+      when json_template.exist?
+        json_template
+      when yaml_template.exist?
+        yaml_template
+      else
+        raise "CloudFormation template not found at #{json_template_path} "\
+              "or #{yaml_template_path}!" unless @template_file
+      end
+    end
+
     def stack_parameter_overrides
       overrides.map do |k, v|
         { parameter_key: k, parameter_value: v.to_s }

lib/moonshot/stack_template.rb

@@ -1,7 +1,5 @@
-require 'json'
-
 module Moonshot
-  # A StackTemplate loads the JSON template from disk and stores information
+  # A StackTemplate loads the template from disk and stores information
   # about it.
   class StackTemplate
     Parameter = Struct.new(:name, :default) do
@@ -10,30 +8,23 @@ def required?
       end
     end
 
-    attr_reader :body
-
     def initialize(filename, log:)
       @log = log
-
-      unless File.exist?(filename)
-        @log.error("Could not find CloudFormation template at #{filename}")
-        raise
-      end
-
-      # The maximum TemplateBody length is 51,200 bytes, so we remove
-      # formatting white space.
-      @body = JSON.parse(File.read(filename)).to_json
+      @filename = filename
     end
 
     def parameters
-      JSON.parse(@body).fetch('Parameters', {}).map do |k, v|
+      template_body.fetch('Parameters', {}).map do |k, v|
         Parameter.new(k, v['Default'])
       end
     end
 
-    # Return a list of defined resource names in the template.
     def resource_names
-      JSON.parse(@body).fetch('Resources', {}).keys
+      template_body.fetch('Resources', {}).keys
+    end
+
+    def exist?
+      File.exist?(@filename)
     end
   end
 end

lib/moonshot/yaml_stack_template.rb

@@ -0,0 +1,17 @@
+require 'yaml'
+require_relative 'stack_template'
+
+module Moonshot
+  # Handles YAML formatted AWS template files.
+  class YamlStackTemplate < StackTemplate
+    def body
+      template_body.to_yaml
+    end
+
+    private
+
+    def template_body
+      @template_body ||= YAML.load_file(@filename)
+    end
+  end
+end

spec/fs_fixtures/cloud_formation/rspec-app.yml

@@ -0,0 +1,6 @@
+---
+- Resources:
+- Parameters:
+  - Parent1:
+    - Type: String
+    - Description: This is imported from the parent stack on create.

spec/moonshot/stack_spec.rb

@@ -139,4 +139,35 @@
       expect(subject.parameters_file).to eq(path)
     end
   end
+
+  describe '#template' do
+    let(:yaml_path) { File.join(Dir.pwd, 'cloud_formation', 'rspec-app.yml') }
+    let(:json_path) { File.join(Dir.pwd, 'cloud_formation', 'rspec-app.json') }
+
+    context 'when there is a template file in both formats' do
+      it 'should prefer the JSON formatted template file' do
+        expect(subject.template).to be_an_instance_of(Moonshot::JsonStackTemplate)
+      end
+    end
+
+    context 'when there is only one kind of template file available' do
+      it 'should pick the JSON template file by default' do
+        FakeFS::File.delete(yaml_path)
+        expect(subject.template).to be_an_instance_of(Moonshot::JsonStackTemplate)
+      end
+
+      it 'should fall back to YAML if no JSON template was found' do
+        FakeFS::File.delete(json_path)
+        expect(subject.template).to be_an_instance_of(Moonshot::YamlStackTemplate)
+      end
+    end
+
+    context 'when there is no template file available' do
+      it 'should raise RuntimeError' do
+        [yaml_path, json_path].each { |p| FakeFS::File.delete(p) }
+
+        expect { subject.template }.to raise_error(RuntimeError)
+      end
+    end
+  end
 end