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This was brought up on the LGTM.com forums here: https://discuss.lgtm.com/t/warn-when-always-failing-assert-is-reachable-rather-than-unreachable/2436 Essentially, in a complex chain of `elif` statements, like ```python if x < 0: ... elif x >= 0: ... else: ... ``` the `else` clause is redundant, since the preceding conditions completely exhaust the possible values for `x` (assuming `x` is an integer). Rather than promoting the final `elif` clause to an `else` clause, it is common to instead raise an explicit exception in the `else` clause. During execution, this exception will never actually be raised, but its presence indicates that the preceding conditions are intended to cover all possible cases. I think it's a fair point. This is a clear instance where the alert, even if it is technically correct, is not useful for the end user. Also, I decided to make the exclusion fairly restrictive: it only applies if the unreachable statement is an `assert False, ...` or `raise ...`, and only if said statement is the first in the `else` block. Any other statements will still be reported.
140 lines
2.4 KiB
Python
Executable File
140 lines
2.4 KiB
Python
Executable File
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#Unreachable code
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def f(x):
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while x:
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print (x)
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while 0:
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asgn = unreachable()
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while False:
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return unreachable()
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while 7:
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print(x)
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def g(x):
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if False:
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unreachable()
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else:
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reachable()
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print(x)
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return 5
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for x in first_unreachable_stmt():
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raise more_unreachable()
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def h(a,b):
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if True:
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reachable()
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else:
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unreachable()
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def intish(n):
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""""Regression test - the 'except' statement is reachable"""
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test = 0
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try:
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test += n
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except:
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return False
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return True
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#ODASA-2033
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def unexpected_return_result():
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try:
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assert 0, "async.Return with argument inside async.generator function"
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except AssertionError:
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return (None, sys.exc_info())
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#Yield may raise -- E.g. in a context manager
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def handle_yield_exception():
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resources = get_resources()
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try:
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yield resources
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except Exception as exc:
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log(exc)
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#ODASA-ODASA-3790
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def isnt_iter(seq):
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got_exc = False
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try:
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for x in seq:
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pass
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except Exception:
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got_exc = True
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return got_exc
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class Odasa3686(object):
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def is_iterable(self, obj):
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#special case string
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if not object:
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return False
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if isinstance(obj, str):
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return False
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#Test for iterability
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try:
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None in obj
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return True
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except TypeError:
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return False
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def odasa5387():
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try:
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str
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except NameError: # Unreachable 'str' is always defined
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pass
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try:
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unicode
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except NameError: # Reachable as 'unicode' is undefined in Python 3
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pass
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#This is OK as type-hints require it
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if False:
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from typing import Any
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def foo():
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# type: () -> None
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return
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#ODASA-6483
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def deliberate_name_error(cond):
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if cond:
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x = 0
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try:
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x
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except NameError:
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x = 1
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return x
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#ODASA-6783
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def emtpy_gen():
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if False:
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yield None
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def foo(x):
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if True:
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if x < 3:
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print(x, "< 3")
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if x == 0:
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print(x, "== 0")
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# Unreachable catch-all case
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def unreachable_catch_all_assert_false(x):
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if x < 0:
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return "negative"
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elif x >= 0:
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return "positive"
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else:
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assert False, x
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def unreachable_catch_all_raise(x):
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if x < 0:
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pass
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elif x >= 0:
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pass
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else:
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raise ValueError(x)
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