Consider supporting an 'include' directive

[eddelbuettel]

In a number of use cases, YAML files are carried over from other, similar files. An example may be YAML frontmatter for Rmarkdown files: certain formatting aspects (say, particular to an author or institution) are copied around from project to project.

In other languages, common elements can re-use by means of an #include somefile statement.
And at least one other YAML parser implements this in the context of a larger system for home automation.

This carried over from here and subsequent email discussion. Having an include directive is yaml is probably easier than attempting to change pandoc or rmarkdown, and the issue really is local to the yaml frontmatter.

/cc @aaronwolen

[viking]

The easiest way to accomplish this right now is through the use of a !include tag and a custom handler:

yaml.load_file("test.yml", handlers = list(include = function(fn) yaml.load_file(fn)))

That would only work for 1 level deep, but you could create a wrapper function to do infinite recursion:

foo <- function(...) yaml.load_file(..., handlers = list(include = foo))
foo("test.yml")

[eddelbuettel]

Nice. One level may actually be good enough for us.

[spgarbet]

Can be done via handlers.

[eddelbuettel]

Can be done via handlers.

It's been years since I would have needed this but I am still curious so how? Can you post a short example, here or in the package?