Partial Compiler

This is very beta right now, not suggested for production projects at the moment

Partial Compiler allows you to execute your code in a single template file in production environments.

gem 'partial_compiler'

Initializer

Create an initializer file:

config/initializers/partial_compiler.rb

# Optional config
PartialCompiler.configure({
 
})

PartialCompiler.start # Required

Default Configuration:

 {
    template_engine: "ERB",
    original_extension: "html.erb",
    rendering_engine_partial_format: "= render partial:",
    regex_partial_eval_match: /(render .*)%>/,
    run_compiled: !Rails.env.development?
 }

run_compiled is likely going to be the only thing you'll want to change. This just tells PC when to use the .compiled file and when to use the .uc file.

File Names

To get PC to recognize your files, you'll need to change the extensions.

index.html.erb will need to become index.uc.html.erb Notice the 'uc' before 'html' Don't create a copy, simply change the file extension.

This only needs to be done for files you want to compile. Do not change the extension of your partials

Using with Haml

TL;DR For now, don't do it.

After testing this in a production application using Haml, this gem will actually slow down your load times when compiled. I'm not 100% sure why. I am looking into this since LunchTray does use a lot of partials and Haml.

For PC, locals are currently only set up to work with ERB, meaning everytime you run the compiler you'll need to convert from ERB to Haml. Icky.

Given a file like:

index.uc.html.erb

Partial Compiler will find all of the partials in said file, extract the code, and create a new file:

index.compiled.html.erb

What's neat is PC will only register template handlers for uc.html.erb in development and compiled.html.erb in production. Meaning you can continue to use your partials in development.

If you have a template and a partial like:

index.uc.html.erb

<div class="container">
  My code in a container
</div>
<span>
  <%= render partial: "my_awesome_partial" %>
</span>

_my_awesome_partial.html.erb

<h1>Look! I'm in a partial!</h1>
<ul>
  <li>Red Potato</li>
  <li>Hot Potato</li>
  <li>French Potato</li>
</ul>

Partial Compiler will turn this into:

index.compiled.html.erb

<div class="container">
  My code in a container
</div>
<span>
  <h1>Look! I'm in a partial!</h1>
  <ul>
    <li>Red Potato</li>
    <li>Hot Potato</li>
    <li>French Potato</li>
  </ul>
</span>

Because of the way we pluck the information from partials, you cannot directly pass a variable or method as a local unless it's an instance variable.

For locals, the keys cannot share a name with variables in the template. Let me explain:

Assume you have a template that looks like this:

<% my_awesome_variable = "Welcome" %>
<div class="container">
  <h1>
    <%= render partial: "my_partial", locals: {my_awesome_variable: "Goodbye"} %>
  </h1>
  <p><%= my_awesome_variable %></p>
</div>

The uncompiled version will work exactly as you'd expect. The H1 will print out "Goodbye" and the paragraph will print out "Welcome."

At the moment, when locals are inserted into the compiled template, they're added just above where the partial was rendered:

<% my_awesome_variable = "Welcome" %>
<div class="container">
  <h1>
    <% my_awesome_variable = "Goodbye" %>
    <div>
      <%= my_awesome_variable %>
    </div>
  </h1>
  <p><%= my_awesome_variable %></p>
</div>

So now both your H1 and paragraph will say "Goodbye"!

Long story short, just make sure your variables and locals are different names. Also, please excuse my wacky HTML, I don't actually write like that ;)

Partials must be rendered on their own line.

Instead of this:

<h1><%= render partial: "my_partial" %></h1>

Do this:

<h1>
  <%= render partial: "my_partial" %>
</h1>

Indentation, however, will be honoured.

1. Refactor compiler.rb file
2. Allow locals and template variables to share the same name
3. Haml support
4. Slim Support