From a8173630eac1f35914fdc2d918a636ac268b9033 Mon Sep 17 00:00:00 2001
From: Dylan Baker <dylan@pnwbakers.com>
Date: Mon, 1 May 2017 15:11:01 -0700
Subject: Don't use len() to test emptiness vs not emptiness

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.
---
 mesonbuild/modules/gnome.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'mesonbuild/modules/gnome.py')

diff --git a/mesonbuild/modules/gnome.py b/mesonbuild/modules/gnome.py
index b4dfd12..134060f 100644
--- a/mesonbuild/modules/gnome.py
+++ b/mesonbuild/modules/gnome.py
@@ -566,7 +566,7 @@ class GnomeModule(ExtensionModule):
         return ModuleReturnValue(rv, rv)
 
     def compile_schemas(self, state, args, kwargs):
-        if len(args) != 0:
+        if args:
             raise MesonException('Compile_schemas does not take positional arguments.')
         srcdir = os.path.join(state.build_to_src, state.subdir)
         outdir = state.subdir
-- 
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