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Add a tag extension to plumber2

Source: R/extension_tags.R
add_plumber2_tag.Rd

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.

Usage

add_plumber2_tag(tag, handler = NULL)

Arguments

tag

The name of the tag

handler

A handler function for the tag. See Details

Value

This function is called for its side effects

Details

The handler argument must be, if provided, 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 env argument contains the environment the annotation file is evaluated in. The function must return a modified version of block unless block is of the class plumber2_empty_block in which case it is allowed to construct a new object from scratch. If you add a subclass to block you should make sure that a method for apply_plumber2_block() for the subclass exists.

If handler is NULL then the tag will be registered but no associated handler will be added. This can make sense if you have a new block type that consists of multiple tags but only want a single handler for it. In that case you register a handler for one of the required tags and register the remaining tags without a handler.

See also

apply_plumber2_block()

Examples

# Add a tag that says hello when used
add_plumber2_tag("hello", function(block, call, tags, values, env) {
  message("Hello")
  class(block) <- c("hello_block", class(block))
  block
})