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Add default #render_in implementation to ActiveModel::Conversion#57349

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guilleiguaran merged 1 commit into
rails:mainfrom
seanpdoyle:active-model-conversion-render-in
May 12, 2026
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Add default #render_in implementation to ActiveModel::Conversion#57349
guilleiguaran merged 1 commit into
rails:mainfrom
seanpdoyle:active-model-conversion-render-in

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@seanpdoyle

@seanpdoyle seanpdoyle commented May 12, 2026 •
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Motivation / Background

Follow-up to #50623
Follow-up to #46202

The #render_in method was introduced as an integration touch-point for views to intercept object rendering conventionally handled by Action View.

This PR aims to provide Active Model-level (and therefore Active Record-level) flexibility to control how Action View transform models into HTML and JSON strings.

For example, users of the view_component gem can "intercept" model rendering to directly an instance to a ViewComponent::Base instance.

Detail

With the following view partial:

<%# app/views/people/_person.html.erb %>

<%= local_assigns[:shout] ? person.name.upcase : person.name %>

Callers can render an instance of Person as a positional argument or a :renderable option:

person = Person.new(name: "Ralph")

render person                                       # => "Ralph"
render person, shout: true                          # => "RALPH"
render renderable: person                           # => "Ralph"
render renderable: person, locals: { shout: true }  # => "RALPH"

This change aims to preserve backward compatibility by providing a default #render_in method to relies on render the instance with a view partial inferred from combining partial: to_partial_path and object: self.

Checklist

Before submitting the PR make sure the following are checked:

  • This Pull Request is related to one change. Unrelated changes should be opened in separate PRs.
  • Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
  • Tests are added or updated if you fix a bug or add a feature.
  • CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.

@seanpdoyle
Add default #render_in implementation to ActiveModel::Conversion
241f2a0 
Follow-up to [rails#46202][]

Without overriding the new `#render_in` method, previous behavior will
be preserved: render the view partial determined by calling
`#to_partial_path`, then pass `object: self`.

With the following view partial:

```erb
<%# app/views/people/_person.html.erb %>
<% local_assigns.with_defaults(shout: false) => { shout: } %>

<%= shout ? person.name.upcase : person.name %>
```

Callers can render an instance of `Person` as a positional argument or a
`:renderable` option:

```ruby
person = Person.new(name: "Ralph")

render person                                       # => "Ralph"
render person, shout: true                          # => "RALPH"
render renderable: person                           # => "Ralph"
render renderable: person, locals: { shout: true }  # => "RALPH"
```

This preserves backward compatibility. At the same time, the
`#render_in` method provides applications with an more flexibility, and
an opportunity to manage how to transform models into Strings. For
example, users of ViewComponent can map a model directly to a
`ViewComponent::Base` instance.

[rails#46202]: rails#46202 (comment)
@seanpdoyle seanpdoyle mentioned this pull request May 12, 2026
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@guilleiguaran guilleiguaran merged commit 54660ef into rails:main May 12, 2026
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@tahsin352 tahsin352 mentioned this pull request May 15, 2026
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@claudiob

claudiob commented May 15, 2026

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@seanpdoyle Thanks for this PR! Unfortunately this broke my Rails app.

I'm going to try to create a trimmed down version of the app to better identify the issue.
Meanwhile I'll describe it here, maybe this can help already.

I have a standard route/controller for an update action. The update action is defined like this:

# app/controllers/api/bookings_controller.rb
class API::BookingsController < ApplicationController
  def create
    @booking = Booking.find params.expect(:id)
    @booking.update update_params
    response.status = :ok
  end
end

Since I'm not calling render, Rails automatically find the matching view to render, a JBuilder file:

# app/views/api/bookings/update.json.jbuilder
json.partial! @booking

Since I'm not specifying which partial to render, Rails would automatically find this matching one:

# app/views/api/bookings/_booking.json.jbuilder
json.extract! booking, :id, :status

This last part is what's broken after this PR. json.partial! @booking doesn't look for the _booking.json.builder partial in the same folder:

Error:
API::BookingsControllerTest#test_PUT_/api/bookings_responds_with_200_with_valid_authentication_and_params:
RuntimeError: Neutered Exception ActionView::Template::Error: Missing partial bookings/_booking with {locale: [:en], formats: [:json], variants: [], handlers: [:raw, :erb, :html, :builder, :ruby, :jbuilder]}.

Searched in:
  * "/Users/claudiob/code/fountain/app/views"
  * "/Users/claudiob/source/rails/actiontext/app/views"
  * "/Users/claudiob/source/rails/actionmailbox/app/views"

    app/views/api/bookings/update.json.jbuilder:1
    test/controllers/api/bookings_controller_test.rb:33:in 'block in <class:BookingsControllerTest>'
    test/controllers/api/base_controller_test.rb:6:in 'block in <class:BaseControllerTest>'

Let me know if any of this rings a bell. Happy to share a more complete example if that's needed.
Thank you 🙇

@seanpdoyle seanpdoyle mentioned this pull request May 15, 2026
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@seanpdoyle

seanpdoyle commented May 15, 2026

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@claudiob thank you for sharing that context.

@guilleiguaran I've opened #57374 to revert this PR. I'll open a follow-up to incorporate tests that exercise the use-case outlined by @claudiob.

guilleiguaran pushed a commit that referenced this pull request May 15, 2026
@seanpdoyle
Revert "Add default #render_in implementation to `ActiveModel::Conv…
b830aac 
…ersion`"

This reverts commit 241f2a0.

Based on a [comment][] on the original PR ([#57349][]), the `render`
call does not incorporate controller-based view partial namespacing
based on the render context.

Since `ActiveModel::Conversion#render_in` is not yet released, this
commit reverts the change in favor of a subsequent re-submission of the
original PR to incorporate the newly documented edge case.

[comment]: #57349 (comment)
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3 participants

@seanpdoyle @claudiob @guilleiguaran