templates: add filter to reverse list
The filter supports only lists because for lists, it’s straightforward to
implement. Reversing text doesn’t seem very useful and is hard to implement.
Reversing the bytes would break multi-bytes encodings. Reversing the code
points would break characters consisting of multiple code points. Reversing
graphemes is non-trivial without using a library not included in the standard
library.
from mercurial import extensions
def genwrapper(x):
def f(orig, *args, **kwds):
return [x] + orig(*args, **kwds)
f.x = x
return f
def getid(wrapper):
return getattr(wrapper, 'x', '-')
wrappers = [genwrapper(i) for i in range(5)]
class dummyclass:
def getstack(self):
return ['orig']
dummy = dummyclass()
def batchwrap(wrappers):
for w in wrappers:
extensions.wrapfunction(dummy, 'getstack', w)
print('wrap %d: %s' % (getid(w), dummy.getstack()))
def batchunwrap(wrappers):
for w in wrappers:
result = None
try:
result = extensions.unwrapfunction(dummy, 'getstack', w)
msg = str(dummy.getstack())
except (ValueError, IndexError) as e:
msg = e.__class__.__name__
print('unwrap %s: %s: %s' % (getid(w), getid(result), msg))
batchwrap(wrappers + [wrappers[0]])
batchunwrap(
[
(wrappers[i] if i is not None and i >= 0 else None)
for i in [3, None, 0, 4, 0, 2, 1, None]
]
)
wrap0 = extensions.wrappedfunction(dummy, 'getstack', wrappers[0])
wrap1 = extensions.wrappedfunction(dummy, 'getstack', wrappers[1])
# Use them in a different order from how they were created to check that
# the wrapping happens in __enter__, not in __init__
print('context manager', dummy.getstack())
with wrap1:
print('context manager', dummy.getstack())
with wrap0:
print('context manager', dummy.getstack())
# Bad programmer forgets to unwrap the function, but the context
# managers still unwrap their wrappings.
extensions.wrapfunction(dummy, 'getstack', wrappers[2])
print('context manager', dummy.getstack())
print('context manager', dummy.getstack())
print('context manager', dummy.getstack())
# Wrap callable object which has no __name__
class callableobj:
def __call__(self):
return ['orig']
dummy.cobj = callableobj()
extensions.wrapfunction(dummy, 'cobj', wrappers[0])
print('wrap callable object', dummy.cobj())