Mercurial > hg
view tests/test-ui-verbosity.py.out @ 33807:b70029f355a3
tests: verify that peer instances only expose interface members
Our abstract interfaces are more useful if we guarantee that
implementations conform to certain rules. Namely, we want to ensure
that objects implementing interfaces don't expose new public
attributes that aren't part of the interface. That way, as long as
consumers don't access "internal" attributes (those beginning with
"_") then (in theory) objects implementing interfaces can be swapped
out and everything will "just work."
We add a test that enforces our "no public attributes not part
of the abstract interface" rule.
We /could/ implement "interface compliance detection" at run-time.
However, that is littered with problems.
The obvious solutions are custom __new__ and __init__ methods.
These rely on derived types actually calling the parent's
implementation, which is no sure bet. Furthermore, __new__ and
__init__ will likely be called before instance-specific attributes
are assigned. In other words, they won't detect public attributes
set on self.__dict__. This means public attribute detection won't
be robust.
We could work around lack of robust self.__dict__ public attribute
detection by having our interfaces implement a custom __getattribute__,
__getattr__, and/or __setattr__. However, this incurs an undesirable
run-time penalty. And, subclasses could override our custom
method, bypassing the check.
The most robust solution is a non-runtime test. So that's what this
commit implements. We have a generic function for validating that an
object only has public attributes defined by abstract classes. Then,
we instantiate some peers and verify a newly constructed object
plays by the rules.
Differential Revision: https://phab.mercurial-scm.org/D339
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Thu, 10 Aug 2017 21:00:30 -0700 |
parents | 807f3f5c60e9 |
children |
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hgrc settings command line options final result quiet verbo debug quiet verbo debug quiet verbo debug 0 False False False False False False -> False False False 1 True False False False False False -> True False False 2 False True False False False False -> False True False 3 True True False False False False -> False False False 4 False False True False False False -> False True True 5 True False True False False False -> False True True 6 False True True False False False -> False True True 7 True True True False False False -> False True True 8 False False False True False False -> True False False 9 True False False True False False -> True False False 10 False True False True False False -> True False False 11 True True False True False False -> True False False 12 False False True True False False -> True False False 13 True False True True False False -> True False False 14 False True True True False False -> True False False 15 True True True True False False -> True False False 16 False False False False True False -> False True False 17 True False False False True False -> False True False 18 False True False False True False -> False True False 19 True True False False True False -> False True False 20 False False True False True False -> False True False 21 True False True False True False -> False True False 22 False True True False True False -> False True False 23 True True True False True False -> False True False 24 False False False True True False -> False False False 25 True False False True True False -> False False False 26 False True False True True False -> False False False 27 True True False True True False -> False False False 28 False False True True True False -> False False False 29 True False True True True False -> False False False 30 False True True True True False -> False False False 31 True True True True True False -> False False False 32 False False False False False True -> False True True 33 True False False False False True -> False True True 34 False True False False False True -> False True True 35 True True False False False True -> False True True 36 False False True False False True -> False True True 37 True False True False False True -> False True True 38 False True True False False True -> False True True 39 True True True False False True -> False True True 40 False False False True False True -> False True True 41 True False False True False True -> False True True 42 False True False True False True -> False True True 43 True True False True False True -> False True True 44 False False True True False True -> False True True 45 True False True True False True -> False True True 46 False True True True False True -> False True True 47 True True True True False True -> False True True 48 False False False False True True -> False True True 49 True False False False True True -> False True True 50 False True False False True True -> False True True 51 True True False False True True -> False True True 52 False False True False True True -> False True True 53 True False True False True True -> False True True 54 False True True False True True -> False True True 55 True True True False True True -> False True True 56 False False False True True True -> False True True 57 True False False True True True -> False True True 58 False True False True True True -> False True True 59 True True False True True True -> False True True 60 False False True True True True -> False True True 61 True False True True True True -> False True True 62 False True True True True True -> False True True 63 True True True True True True -> False True True