Allow partials accept blocks

[lolmaus]

It is awesome how Jade allows you to call mixins with different options and content blocks.

Jade:

mixin article(title)
  .article
    .article-wrapper
      h1= title
      if block
        block
      else
        p No content provided

+article('Hello world')

+article('Good news, everyone!')
  p This is my
  p Amazing article

The same functionality is found in Sass, but surprisingly is missing in Padrino's template engines. Padrino has partials functionality abstracted out of template engines into a Padrino helper, and Padrino partial helper does not accept content blocks! :(

Middleman introduces the wrap_layout helper that lets you pass a block to a layout (which in this case is almost the same as partial). Unfortunately, it does not accept options, so you can't, for example, pass local variables. :( Also, migrating partials into templates would be an ugly workaround.

I've managed to mimic the desired funcitonality by leveraging Padrino's capture_html. Here's an already working example (in Middleman):

Partial _test.haml:

- if defined? block
  = block
- else
  Welcome, friend

Page index.html.haml:

// Calling the partial without a block
= partial 'test'

// Preparing a block
- captured_html = capture_html do
  %h2 Wassup!

// Calling the partial with a block
= partial 'test', locals: { block: captured_html }

But this approach is also kinda ugly because it requires to write a block before partial call and use an ad-hoc variable to store it.

Note: you can't use content_for for this purpose because contents of content_for is accumulated rather than redefined when you use it multiple times.

I also tried creating a helper instead of a partial-that-accepts-a-block. It made using the helper-partial awesomely clean, just as i request. But the HTML of the helper-partial had to be written in Ruby strings and assembled via content_tag in reverse order, which is very ugly. :(

So i suggest the following syntax for Padrino partials. It is just a concept and open for discussion.

Haml:

// Calling the partial without a block
= partial 'title', class: 'first-title'

// Calling the same partial with a block
= partial 'test', class: 'second-title' do
  %h2 Wassup!

Also, please have a look at how DerbyJS allows passing multiple blocks to a partial.

DerbyJS + Jade:

  app:shared:header // Calling the partial
    @left
      label
        input(type='checkbox', checked='{_page.user.data.prof}')/
        | Professor (Create new game)
    @right
      a.icon-admin(href='/admin') Admin Panel

I wonder whether something similar can be done in Padrino without falling back to the capture_html workaround.

[ujifgc]

@lolmaus thank you for your suggestion. Does the commit do what you wanted?

[lolmaus]

This is awesome, @ujifgc! I can't believe how quick and kind you've been to implement it.

Unfortunately, this bug in Middleman prevents me from trying it out. But it seems to be exactly what i was hoping for. Thank you Igor!

When is this going to hit RubyGems?

[lolmaus]

I tried manually creating a helper with your code in a sandbox Middleman project and it didn't work out. :(

yield within a partial produces the following error:

NameError at /
undefined local variable or method `layout_dir' for #Middleman::Application:0x32188944
raise "Tried to render a layout (calls yield) at #{path} like it was a template. Non-default layouts need to be in #{source}/#{layout_dir}."

[lolmaus]

@ujifgc Igor, are you going to work on this further?

I'm not good in Ruby enough to try finishing this on my own. I even failed to find where yield is defined.

[ujifgc]

Yes, later. Not right away.

[ujifgc]

@lolmaus could you sketch up a broken test app and publish it at github? I never used middleman before.

[lolmaus]

Here you go: https://github.com/lolmaus/middleman-padrino-test-partial-block

It's not producing an error as i had said (have you added commits?), but it doesn't work as expected.

I've got a partial:

%h1 prefix
.haml-block
  = yield
%h3 postfix

I call it like this:

= partial 'foo' do
  Am i the only one around here who has this failing?

Resulting HTML:

    Am i the only one around here who has this failing?
<h1>prefix</h1>
<div class="haml-block">
  0
</div>
<h3>postfix</h3>

[ujifgc]

I fixed the issue and added a test.

I'm aware that middleman stays broken but it's because recent improvements to padrino rendering extensions. The problem is, as I understand, the monkey patch https://github.com/middleman/middleman/blob/master/middleman-core/lib/middleman-more/core_extensions/default_helpers.rb#L74 that expects old code.

[lolmaus]

Do you see how Middleman can be fixed?

[ujifgc]

Investigate the reasons of monkey patching, remove them. Or patch to use
new storage of rendering extensions.
On Nov 29, 2013 11:26 AM, "lolmaus" notifications@github.com wrote:

Do you see how Middleman can be fixed?

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/1504#issuecomment-29500076
.

[lolmaus]

@ujifgc, Igor, can you please open an issue ticket for Middleman, explain the problem in detail and state your suggestions? I don't want to play Chinese whispers here.

[ujifgc]

No, I'm sorry, I don't use Middleman. I looked at their code and can't figure out what are they trying to do with our helpers and why. I can guess that's some patching needed on version 0.11.4.

[lolmaus]

Thank you @ujifgc. ^__^