The AV::Base constructor was too complicated, and this commit tightens
up the parameters it will take. At runtime, AV::Base is most commonly
constructed here:
94d54fa4ab/actionview/lib/action_view/rendering.rb (L72-L74)
This provides an AV::Renderer instance, a hash of assignments, and a
controller instance. Since this is the common case for construction, we
should remove logic from the constructor that handles other cases. This
commit introduces special constructors for those other cases.
Interestingly, most code paths that construct AV::Base "strangely" are
tests.
Previously, when content_for is flushed, the content
was replaced directly by a new value in
ActionView::OutputFlow#set. The problem is this new
value passed to the method may not be an instance of
ActiveSupport::SafeBuffer.
This change forces the value to be set to a new
instance of ActiveSupport::SafeBuffer.
This has been discussed in #17661 and partially reverts the changes made
in 9de83050d3 and 986cac73e3
The test case added to content_for acts as a regression / acceptance test.
