Introduce ActionView::TestCase.register_parser

[seanpdoyle]

Motivation / Background

Register a callable to decode rendered content for a given MIME type

Each registered parser will also define a #rendered.$MIME helper method, where $MIME corresponds to the value of the mime argument.

Detail

Arguments

mime - Symbol the MIME Type name for the rendered content callable - Callable to decode the String. Accepts the String
value as its only argument
block - Block serves as the parser when the
callable is omitted

By default, ActionView::TestCase defines a parser for:

• :html - returns an instance of Nokogiri::XML::Node
• :json - returns an instance of ActiveSupport::HashWithIndifferentAccess

Each pre-registered parser also defines a corresponding helper:

• :html - defines rendered.html
• :json - defines rendered.json

Examples

To parse the rendered content into RSS, register a call to RSS::Parser.parse:

register_parser :rss, -> rendered { RSS::Parser.parse(rendered) }

test "renders RSS" do
  article = Article.create!(title: "Hello, world")

  render formats: :rss, partial: article

  assert_equal "Hello, world", rendered.rss.items.last.title
end

To parse the rendered content into a Capybara::Simple::Node, re-register an :html parser with a call to
Capybara.string:

register_parser :html, -> rendered { Capybara.string(rendered) }

test "renders HTML" do
  article = Article.create!(title: "Hello, world")

  render partial: article

  rendered.html.assert_css "h1", text: "Hello, world"
end

For the sake of backwards compatibility, re-define existing support for document_root_element in terms of rendered.html.

Additional information

This proposal draws inspiration from ActionDispatch::Testing::RequestEncoder, and the response.parsed_body test method that it enables.

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Changes that are unrelated 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]

@rafaelfranca this proposal is in the same spirit of the work merged as part of #49003.

[seanpdoyle]

@rafaelfranca is this class a Content descendant for troubleshooting and naming purposes? Could it be default: Class.new(SimpleDelegator) directly, cutting out the Content class entirely?

[rafaelfranca]

It doesn't need to be a descendant. I just changed that. But I prefer to have a name for debug purpose, and documentation so people can search. I just used the Ruby 3.3 set_temporary_name if it is present.