Clarify how to render the "default content" passed to a partial

[adamlogic]

I ran into a bit of confusion integrating Nice Partials into some existing partials that were calling <%= yield %>.

This raised an error after I added the p block variable into the caller because p is nil when calling yield without an argument:

    <%= render "fieldset", legend: "Autoscaling" do |p| %>
      <% p.content_for :actions do %>
        TEST
      <% end %>

      ... the main content

The solution (I think) is to capture the result of yield p = np and use it instead of calling yield again:

<% content = yield(p = np) %>

<div class="divide-y pb-6">
  <div class="flex justify-between items-center">
    <legend class="text-2xl font-medium pb-6"><%= legend %></legend>

    <% if p.content_for? :actions %>
      <%= p.yield :actions %>
    <% end %>
  </div>

  <%= content %>
</div>

Assuming I'm following the recommended approach here, I think this probably just needs a little documentation in the README.

[kaspth]

In #32 we just added the ability to remove yield(p = np) and just refer to p directly (note: we're debating other names in #36)

To your question, in #32, we also added p.output_buffer which has the captured output like your content = yield(p = np) does. So on main you're able to do:

<div class="divide-y pb-6">
  <div class="flex justify-between items-center">
    <legend class="text-2xl font-medium pb-6"><%= legend %></legend>

    <% if p.content_for? :actions %>
      <%= p.yield :actions %>
    <% end %>
  </div>

  <%= p.output_buffer %>
</div>

So I'll close this as fixed for now.

[adamlogic]

👏 Thanks for the detailed follow-up!

Any thoughts on calling p.yield with no arguments instead of (or in addition to) p.output_buffer? This would align nicely with how yield is used in Rails layouts, and it would feel a bit more "supported".

By "supported", I mean that calling output_buffer feels a bit like I'm going off the happy path and using an internal API. Perhaps that's intentional?

[adamlogic]

I just pointed my app to the main branch here so I could try out this change, and I'm having a problem when calling the partial with no arguments.

Here is my (simplified) partial:

<div>
  <%= p.yield :actions %>
  <%= p.output_buffer %>
</div>

When I render this partial with an argument (render "fieldset" do |p|) it works as expected, but when I render without an argument (render "fieldset" do), p.output_buffer does not output the content.

It does work as expected when I use the old style:

<% content = yield(p = np) %>

<div>
  <%= p.yield :actions %>
  <%= content %>
</div>

[seanpdoyle]

Any thoughts on calling p.yield with no arguments instead of (or in addition to) p.output_buffer? This would align nicely with how yield is used in Rails layouts, and it would feel a bit more "supported".

I was going to suggest the same method name! I'm in favor of this proposal.

When I render this partial with an argument (render "fieldset" do |p|) it works as expected, but when I render without an argument (render "fieldset" do), p.output_buffer does not output the content.

The changes made in #32 hinge on a check on the number of arguments passed to the partial's block: when its arity is one, the block is made available, otherwise, it isn't.

I believe the check aims prevent breaking backwards compatibility and tries to avoid disrupting the default partial rendering process with extra or conflicting variables names.

[kaspth]

Hm, I'm not quite liking p.yield because all this yield stuff is already confusing enough as is. I think I'd rather have p.captured_content or similar.

That said, for @seanpdoyle's last example here #27 (comment), it would be interesting if you could do:

<%# app/views/application/_form.html.erb %>
<% form_options = local_assigns.slice(:model, :url, :id, :data, :html) %>

<%= form_with some_magic_helper_that_can_deeply_merge_attributes_and_tokens(form_options, data: { controller: "form", action: "submit->form#doSomethingSpecial" }) do |form| %>
  <% p.yield form %> <%# <- Call `capture(form, p, &block)` and pass the form along, also passing `p` as the second argument %>
  <%= p.yield :controls %>

  <div>
    <%= link_to "Cancel", :back %>
    <%= p.yield :actions %>
  </div>
<% end %>

<%# elsewhere %>

<%= render "form", model: @post, data: { controller: "special-form", action: "reset->special-form#resetInASpecialWay" } do |form, builder| %>
  <%= builder.controls do %>
    <%= form.label :name %>
    <%= form.text_field :name %>
    <%# ... %>
  <% end %>

  <%= builder.actions do %>
    <%= form.button "Reset", type: "reset" %>
    <%= form.button "Submit" %>
  <% end %>
<% end %>

[kaspth]

Ok, seeing yield in action in #41, I'm good with it.