Compatibility behavior of changing the out_dir is incredibly confusing

[not-my-profile]

I was just getting incredibly confused why lalrpop::Configuration().set_out_dir("out").process_current_dir() wrote the .rs file to the current directory instead of the out/ directory. I looked through the documentation and couldn't find any answer, I looked through the api/mod.rs source code and couldn't find any answer. Only when digging deeper into the source code I found the following:

lalrpop/lalrpop/src/build/mod.rs

Lines 91 to 96 in b777a6a

	// If the lalrpop file is not in in_dir, the result is that the
	// .rs file is created in the same directory as the lalrpop file
	// for compatibility reasons
	Ok(out_dir
	.join(lalrpop_file.strip_prefix(&in_dir).unwrap_or(lalrpop_file))
	.with_extension(ext))

And process_current_dir apparently sets the in_dir to ./src triggering this "compatibility" behavior.

This is so incredibly unintuitive that I think that behavior should either be removed or the Configuration API be deprecated in favor of something more sane.

[youknowone]

@nikomatsakis do you have any idea about this issue?

[nikomatsakis]

I don't remember much of the details here but I definitely think we should clean this up for 1.0. I was trying it out on a recent project and I also hit some issues with a .lalrpop file that was not in the root directory, I think the problem was more that I didn't know what to specify as the path in the lalrpop_mod macro, though.