Package authors can extend plumber2 with their own functionalities. If they wish to add a new tag to be used when writing annotated plumber2 routes they can use this function. If so, it should be called when the package is loaded.
Details
The handler argument must be a function with the arguments block, call,
tags, values, and env. block is a list with the currently parsed
information from the block. You can add or modify the values within to suit
your need as well as subclass it. You should not remove any values as others
might need them. call is the parsed value of whatever expression was
beneath the plumber2 block. tags is a character vector of all the tags in
the block, and values is a list of all the values associated with the tags
(that is, whatever comes after the tag in the block). The values are
unparsed. You should assume that all tags not relevant for your extension has
already been handled and incorporated into block. The function must return
a modified version of block. If you add a subclass to block you should
make sure that a method for apply_plumber2_block() for the subclass exists.