I got this warning on a build:
> WARNING: Passed invalid keyword argument preset. This will become a hard error in the future.
I had to grep in meson code to understand that "preset" was the name of
the invalid argument. This is not obvious at all depending on the
argument name (here it looked like it was about argument presets).
Let's make it clearer by putting it in quotes.
Meson has a common pattern of using 'if len(foo) == 0:' or
'if len(foo) != 0:', however, this is a common anti-pattern in python.
Instead tests for emptiness/non-emptiness should be done with a simple
'if foo:' or 'if not foo:'
Consider the following:
>>> import timeit
>>> timeit.timeit('if len([]) == 0: pass')
0.10730923599840025
>>> timeit.timeit('if not []: pass')
0.030033907998586074
>>> timeit.timeit('if len(['a', 'b', 'c', 'd']) == 0: pass')
0.1154778649979562
>>> timeit.timeit("if not ['a', 'b', 'c', 'd']: pass")
0.08259823200205574
>>> timeit.timeit('if len("") == 0: pass')
0.089759664999292
>>> timeit.timeit('if not "": pass')
0.02340641999762738
>>> timeit.timeit('if len("foo") == 0: pass')
0.08848102600313723
>>> timeit.timeit('if not "foo": pass')
0.04032287199879647
And for the one additional case of 'if len(foo.strip()) == 0', which can
be replaced with 'if not foo.isspace()'
>>> timeit.timeit('if len(" ".strip()) == 0: pass')
0.15294511600222904
>>> timeit.timeit('if " ".isspace(): pass')
0.09413968399894657
>>> timeit.timeit('if len(" abc".strip()) == 0: pass')
0.2023209120015963
>>> timeit.timeit('if " abc".isspace(): pass')
0.09571301700270851
In other words, it's always a win to not use len(), when you don't
actually want to check the length.
To reproduce, one could write:
foo = files('foo.c')
foo[0].path()
and get:
Traceback (most recent call last):
[snip]
File "/home/trhd/Projects/meson/mesonbuild/interpreterbase.py", line 398, in method_call
raise InvalidArguments('Variable "%s" is not callable.' % object_name)
UnboundLocalError: local variable 'object_name' referenced before assignment
Fix this by handling file objects separately.
Jussi Pakkanen
Jehan
Elliott Sales de Andrade
Dylan Baker
Hemmo Nieminen
Nirbheek Chauhan
Mike Sinkovsky
Igor Gnatenko