Prepend title comments to each chunks. By default, title is the name of the corresponding chunk engines.

hook_title_comment(
trigger = "title",
default = "{engine}",
args = list(),
.set = TRUE
)

Arguments

trigger A name of chunk option triggers the hook. A string or function as a default value of the triggering chunk option. If string, the value is given to glue::glue, and evaluates the expression by setting chunk options as an environment, and then automatically commented out. If function, it must have options parameter which receives chunk options, and return a string. A list of arguments given to glue::glue() or callable default. TRUE or FALSE to set a default value and a hook to the trigger.

comment_title(), comment_out(), comment_syntax()

Examples

# Set hook which comments engine names of each chunks at the beginning.
hook_title_comment()

# Customize format
# For R chunks, let title comment be something like "chunk-label.R".
# Otherwise, fall back to the default behavior.
hook_title_comment(
default = function(options) {
if (options$engine == "R") { return(sprintf("# %s.%s", options$label, options\$engine))
}
return(comment_title(options, template = "{engine}"))
}
)