Prepend title comment to chunks

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.
default	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.
args	A list of arguments given to glue::glue() or callable default.
.set	TRUE or FALSE to set a default value and a hook to the trigger.

See also

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}"))
  }
)