Non-existing parent directories are implicitly created

[justvanrossum]

Non-existing parent directories are implicitly created:

from ufoLib import UFOWriter
import os

p = os.path.expanduser(u"~/Desktop/deeper/and/Deeper/test.ufo")
w = UFOWriter(p)

The deeper/and/Deeper directories are created if they didn't already exist.
This may have been intentional, but I don't think it's good design: a simple typo in a script could silently behave a lot different than intended. A "No such directory" exception would be better.

Btw., this behavior trickles down all the way to the RoboFont scripting level, via defcon :)
Cc @typemytype

[anthrotype]

We should use os.mkdir instead of os.makedirs, at least to create the UFO root directory.
https://docs.python.org/3/library/os.html#os.makedirs

[typesupply]

This was not intentional. It should be changed.

[anthrotype]

this is fixed in master

ufoLib/Lib/ufoLib/__init__.py

Lines 837 to 841 in ccec17d

	dirName = os.path.dirname(path)
	if dirName and not os.path.isdir(dirName):
	raise UFOLibError(
	"Cannot write to '%s': directory does not exist" % path
	)

[anthrotype]

lots of defcon-based tools relied on this behaviour that the output directories where automatically created when missing (MutatorMath for one)
https://travis-ci.org/adobe-type-tools/afdko/jobs/440211784#L2121

I know that raising an error is the correct thing to do for ufoLib when asked to write a UFO to a directory which does not exist yet (as it might have been a mistake), but still..

[anthrotype]

so what should a tool like MutatorMath do when a designspace contains instances' filenames whose directories don't exist?
Should it let ufoLib raise its error "no such directory" and force the user do a preemptive mkdir -p somewhere/over/the/rainbow?

[miguelsousa]

force the user do a preemptive mkdir -p somewhere/over/the/rainbow

Does that mean that the user would have to preemptively create each parent directory of each instance? That's a lot extra setup for projects that do not generate all the instances to the same parent directory. I understand releasing ufoLib from that responsibility, but the tools should take over the burden, not the user.

[anthrotype]

a simple typo in a script could silently behave a lot different than intended.

similarly, a typo in a designspace file could silently behave a lot different than intended