Where is the official documentation for R Markdown YAML frontmatter?

Question

I can't find the official documentation for R Markdown YAML frontmatter, for example for this option:

editor_options:
  chunk_output_type: console

I've looked into R Markdown: The Definitive Guide (which, by the way, it's the book linked from the official R Markdown website) but it's not there.

I've looked into R Markdown Cookbook, it's hinted at here but doesn't look like the official reference.

I've looked into R Markdown Reference guide, it's not there.

I've looked into R Markdown Cheatsheet, it's not there.

Answer 1

There is no official documentation for R Markdown YAML frontmatter because the YAML frontmatter is a collection of metadata and each individual piece of data might or not be used by a piece of software from your tool chain. The mentioned metadata,

editor_options:
  chunk_output_type: console

is used by R Studio to have the code block output "be shown in the R console instead of inside the source editor". This option might be ignored by VSCode or Emacs.