--master-dir '{tmp}' while interpolating

[simoncozens]

For ninja reasons I need to generate instance UFOs separately and in parallel, so I am doing the equivalent of

$ fontmake -i "Noto Sans Hebrew ExtraLight" -o ufo -g NotoSansHebrew.glyphs --instance-dir instance_ufos/ &
$ fontmake -i "Noto Sans Hebrew Light" -o ufo -g NotoSansHebrew.glyphs --instance-dir instance_ufos/ &
$ fontmake -i "Noto Sans Hebrew Regular" -o ufo -g NotoSansHebrew.glyphs --instance-dir instance_ufos/ &
...

(Yes, it would be more efficient to only run fontmake -i once, because otherwise you're redundantly generating all the master UFOs each time. I know.)

However, even running two fontmake -o ufo -i in parallel leads to a race:

$ fontmake -i "Noto Sans Hebrew ExtraLight" -o ufo -g NotoSansHebrew.glyphs --instance-dir instance_ufos/ &; fontmake -i "Noto Sans Hebrew Light" -o ufo -g NotoSansHebrew.glyphs --instance-dir instance_ufos/
[1] 50969
INFO:fontmake.font_project:Building master UFOs and designspace from Glyphs source
INFO:fontmake.font_project:Building master UFOs and designspace from Glyphs source
INFO:glyphsLib.parser:Parsing .glyphs file
INFO:glyphsLib.parser:Parsing .glyphs file
fontmake: Error: In 'master_ufo/NotoSansHebrew-Light.ufo': Writing UFO source failed: [Errno 2] No such file or directory: 'kafrafe-hb.glif'

This is obviously happening because both processes are trying to write to the master_ufo directory at the same time.

I know, I thought; there's an option to allow temporary master_ufo directory. Yet:

$ fontmake -i "Noto Sans Hebrew Condensed Thin" --master-dir '{tmp}' -o ufo -g NotoSansHebrew.glyphs --instance-dir instance_ufos/

fontmake: error: Can't use temporary master directory with 'ufo' output

This error is understandable when the masters are the target of the operation; but it's less useful when the instance UFOs are the target. However, overriding the check when args["interpolate"] is true causes even stranger issues:

fontmake: Error: In 'NotoSansHebrew.glyphs' -> '../../../../../../var/folders/jp/4p0m9zvx2l739tdpflm38kv40000gn/T/master_dir_eoi2bbvr/NotoSansHebrew.designspace': Generating fonts from Designspace failed: [Errno 13] Permission denied: '/var/folders/jp/4p0m9zvx2l739tdpflm38kv40000gn/T/master_dir_eoi2bbvr/../../../../../../Users'

[simoncozens]

I'm not entirely clear why fontmake -i needs to write master UFOs to disk anyway.

[anthrotype]

wait I thought I had removed the need to write master UFOs to disk with #1020... have I not?

[anthrotype]

can you try to use --output-dir instead of --instance-dir?

[anthrotype]

fontmake/Lib/fontmake/font_project.py

Lines 890 to 893 in 6a8b290

	# only save *master* UFOs when explicitly requested: i.e. outputs contain
	# 'ufo' and the -i/--interpolate option was not passed (that's for *instances*)
	# or a --master-dir was set
	save_ufos = "ufo" in output and (not interpolate or master_dir is not None)

fontmake/Lib/fontmake/font_project.py

Lines 951 to 953 in 6a8b290

	# let --output-dir override the instance UFO directory
	if output_dir is not None:
	instance_dir = output_dir

[simoncozens]

You're right; with a new fontmake it works fine. Thanks!