This enables Hash Shorthand / punning on your final template statement (which I think is a good thing).

This was a somewhat tricky error to track down -- but this cropped up for us as I was adding Sorbet strict typing to our view layer. An example repro on Ruby 3.1+ would be:

example/test.json.jbuilder:

foobar = "hello"
json.partial! "example/partial", foobar:

And:

example/_partial.json.jbuilder:

json.baz foobar

This would result in {"baz": "{}"} rather than {"baz": "hello" }.

Ultimately a Jbuilder template compiles to something like:

 def __source_json_jbuilder___2759381185109067391_7700(local_assigns, output_buffer)
            @virtual_path = "source";;__already_defined = defined?(json); json||=JbuilderTemplate.new(self);       content = "hello"
      json.partial! "partial", content:

      json.target! unless (__already_defined && __already_defined != "method")
          end

In cases where the final statement could be construed as still open (spanning newlines), this string munging can take the result of the json.target! and pull it into local_assigns.