New function_brace_linter

[MichaelChirico]

Part of #962

Shall we mark this one as default? I don't see it called out specifically in the style guide.

[MichaelChirico]

We were not totally sure what to do with a case like we see in lintr:

lintr/R/package_hooks_linter.R

Lines 82 to 85 in b91dc57

	function(expr) sprintf(
	"%s() should take two arguments, with the first starting with 'lib' and the second starting with 'pkg'.",
	get_hook(expr)
	),

In the end we decided to enforce that having braces. But we might skip linting this type of usage optionally.

[AshesITR]

https://style.tidyverse.org/syntax.html#inline-statements

It's written explicitly for if () but I think it can be generalized to functions. Happy to have this as a default.

Also note the implicit mention of a leading { in https://style.tidyverse.org/functions.html#long-lines-1

cc @jimhester

[AshesITR]

So, do we make it a default?

[MichaelChirico]

So, do we make it a default?

Yes. Any thoughts on the edge case-y example in the above comment? #987 (comment)

[AshesITR]

I'd lint it. It's not super easy to see at first glance that there is no closing parenthesis on the function definition line.