add cache to precompile mjml files in test env

lib/mjml.rb

@@ -19,7 +19,8 @@ module Mjml
     :raise_render_exception,
     :template_language,
     :validation_level,
-    :use_mrml
+    :use_mrml,
+    :cache_mjml
 
   mattr_writer :valid_mjml_binary
 

lib/mjml/cache.rb

@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+module Mjml
+  class Cache
+    attr_reader :template_path
+
+    def initialize(template_path)
+      @template_path = template_path
+    end
+
+    # @yield [] -> String
+    # @return [String]
+    def cache(&block)
+      return yield if !Mjml.cache_mjml && block
+
+      cached_path = cached_file_path
+      if File.exist?(cached_path)
+        File.read(cached_path)
+      else
+        html_content = yield if block
+        File.write(cached_path, html_content)
+        html_content
+      end
+    end
+
+    private
+
+    def cached_file_path
+      File.join(cache_directory, "#{fingerprint}.html")
+    end
+
+    def fingerprint
+      full_path = File.join(Dir.pwd, 'app', 'views', "#{template_path}.mjml")
+      raise "Template file not found: #{full_path}" unless File.exist?(full_path)
+
+      Digest::SHA256.hexdigest(File.read(full_path))
+    end
+
+    def cache_directory
+      dir = File.join(Dir.pwd, 'tmp', 'mjml_cache')
+      FileUtils.mkdir_p(dir) unless Dir.exist?(dir)
+      dir
+    end
+  end
+end

lib/mjml/handler.rb

@@ -17,6 +17,7 @@ def call(template, source = nil)
       compiled_source = compile_source(source, template)
 
       parser_class = Mjml.use_mrml ? 'MrmlParser' : 'Parser'
+      template_path = template.virtual_path
       # Per MJML v4 syntax documentation[0] valid/render'able document MUST start with <mjml> root tag
       # If we get here and template source doesn't start with one it means
       # that we are rendering partial named according to legacy naming convention (partials ending with '.mjml')
@@ -25,7 +26,7 @@ def call(template, source = nil)
       #
       # [0] - https://github.com/mjmlio/mjml/blob/master/doc/components_1.md#mjml
       if /<mjml.*?>/i.match?(compiled_source)
-        "Mjml::#{parser_class}.new(begin;#{compiled_source};end).render.html_safe"
+        "Mjml::#{parser_class}.new('#{template_path}', begin;#{compiled_source};end).render.html_safe"
       else
         compiled_source
       end

lib/mjml/parser.rb

@@ -1,35 +1,43 @@
 # frozen_string_literal: true
 
+require 'digest'
+require_relative 'cache'
+
 module Mjml
   class Parser
     class ParseError < StandardError; end
 
-    attr_reader :input
+    attr_reader :template_path, :input
 
     # Create new parser
     #
-    # @param input [String] The string to transform in html
-    def initialize(input)
+    # @param template_path [String] The path to the .mjml file
+    # @param input [String] The content of the .mjml file
+    def initialize(template_path, input)
       raise Mjml.mjml_binary_error_string unless Mjml.valid_mjml_binary
 
-      @input = input
+      @template_path = template_path
+      @input         = input
+      @with_cache    = Cache.new(template_path)
     end
 
-    # Render mjml template
+    # Render MJML template
     #
     # @return [String]
     def render
-      in_tmp_file = Tempfile.open(['in', '.mjml']) do |file|
-        file.write(input)
-        file # return tempfile from block so #unlink works later
-      end
-      run(in_tmp_file.path)
-    rescue StandardError
-      raise if Mjml.raise_render_exception
+      @with_cache.cache do
+        in_tmp_file = Tempfile.open(['in', '.mjml']) do |file|
+          file.write(input)
+          file # return tempfile from block so #unlink works later
+        end
+        run(in_tmp_file.path)
+      rescue StandardError
+        raise if Mjml.raise_render_exception
 
-      ''
-    ensure
-      in_tmp_file&.unlink
+        ''
+      ensure
+        in_tmp_file&.unlink
+      end
     end
 
     # Exec mjml command

test/parser_test.rb

@@ -4,7 +4,7 @@
 
 describe Mjml::Parser do
   let(:input) { mock('input') }
-  let(:parser) { Mjml::Parser.new(input) }
+  let(:parser) { Mjml::Parser.new('test_template', input) }
 
   describe '#render' do
     describe 'when exception is raised' do
@@ -42,7 +42,7 @@
         expect(Mjml.beautify).must_equal(true)
         expect(Mjml.minify).must_equal(false)
         expect(Mjml.validation_level).must_equal('strict')
-        expect(Mjml.fonts).must_equal(nil)
+        assert_nil(Mjml.fonts)
       end
 
       it 'uses setup config' do

test/views/test_template.mjml

@@ -0,0 +1,18 @@
+<mjml owa="desktop">
+  <mj-body>
+    <mj-section>
+      <%= render partial: "user_header", formats: [:html] %>
+    </mj-section>
+
+    <mj-section>
+      <mj-column>
+        <mj-text>
+          <h2>We inform you about something</h2>
+          <p>
+            Please visit <a href="https://www.example.com">this link</a>
+          </p>
+        </mj-text>
+      </mj-column>
+    </mj-section>
+  </mj-body>
+</mjml>