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gh-94808: add tests covering PySequence_[InPlace]Concat #99319

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gh-94808: add tests covering PySequence_[InPlace]Concat #99319

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gh-94808: add tests covering `PySequence_[InPlace]Concat`
sobolevn Nov 10, 2022
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sobolevn Nov 25, 2022
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Merge branch 'main' into cover-sequence-concat
sobolevn Mar 24, 2023
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157 changes: 157 additions & 0 deletions Lib/test/test_operator.py
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Original file line number Diff line number Diff line change
Expand Up @@ -505,6 +505,163 @@ def __getitem__(self, other): return 5 # so that C is a sequence
self.assertEqual(operator.ixor (c, 5), "ixor")
self.assertEqual(operator.iconcat (c, c), "iadd")

def test_concat(self):
operator = self.module

# Simple cases:
data1 = [1, 2]
data2 = ['a', 'b']
self.assertEqual(operator.concat(data1, data2), [1, 2, 'a', 'b'])
self.assertEqual(operator.concat(data1, data2), data1 + data2)
self.assertEqual(data1, [1, 2]) # must not change
self.assertEqual(data2, ['a', 'b']) # must not change

data1 = (1, 2)
data2 = ('a', 'b')
self.assertEqual(operator.concat(data1, data2), (1, 2, 'a', 'b'))
self.assertEqual(operator.concat(data1, data2), data1 + data2)
self.assertEqual(data1, (1, 2)) # must not change
self.assertEqual(data2, ('a', 'b')) # must not change

data1 = '12'
data2 = 'ab'
self.assertEqual(operator.concat(data1, data2), '12ab')
self.assertEqual(operator.concat(data1, data2), data1 + data2)
self.assertEqual(data1, '12') # must not change
self.assertEqual(data2, 'ab') # must not change

# Subclasses:
class ListSubclass(list):
pass

data1 = ListSubclass([1, 2])
data2 = ListSubclass(['a', 'b'])

res = operator.concat(data1, data2)
self.assertIsInstance(res, list)
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This doesn't prove anything, does it? Whether the result is a ListSubclass or a plain list, this will always be true. If you want to say something interesting here I'd assert that it isn't a ListSubclass instance.

self.assertEqual(res, [1, 2, 'a', 'b'])
self.assertIsInstance(data1, ListSubclass)
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I don't see the point of this -- of course data1 and data2 are instances of ListSubclass, that's how they were created.

self.assertEqual(data1, ListSubclass([1, 2])) # must not change
self.assertIsInstance(data2, ListSubclass)
self.assertEqual(data2, ListSubclass(['a', 'b'])) # must not change

# Custom type with `__add__`:
class TupleSubclass(tuple):
def __add__(self, other):
return TupleSubclass(other + self)

data1 = TupleSubclass([1, 2])
data2 = ('a', 'b')
res = operator.concat(data1, data2)
self.assertIsInstance(res, TupleSubclass)
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This one is good.

self.assertEqual(res, TupleSubclass(['a', 'b', 1, 2]))
self.assertIsInstance(data1, TupleSubclass)
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But this is still questionable. I can't think of a scenario where this would fail.

Or do you have coverage results showing this is needed? (Where?)

Ditto for data2 and again in the following block of tests.

self.assertEqual(data1, TupleSubclass([1, 2])) # must not change
self.assertIsInstance(data2, tuple)
self.assertEqual(data2, ('a', 'b')) # must not change

# Corner cases:
self.assertEqual(operator.concat([1, 2], []), [1, 2])
self.assertEqual(operator.concat([], [1, 2]), [1, 2])
self.assertEqual(operator.concat([], []), [])

# Type errors:
self.assertRaises(TypeError, operator.concat, [], 1)
self.assertRaises(TypeError, operator.concat, 1, [])
self.assertRaises(TypeError, operator.concat, 1, 1)
self.assertRaises(TypeError, operator.concat, (), [])
self.assertRaises(TypeError, operator.concat, [], ())

# Returns `NotImplemented`:
class BrokenSeq(tuple):
def __add__(self, other):
return NotImplemented

self.assertRaises(TypeError, operator.concat, BrokenSeq(), BrokenSeq())

def test_iconcat(self):
operator = self.module

# Simple cases:
data1 = [1, 2, 3]
data2 = ['a', 'b']
res = operator.iconcat(data1, data2)
self.assertEqual(res, [1, 2, 3, 'a', 'b'])
self.assertEqual(data1, [1, 2, 3, 'a', 'b']) # must change
self.assertEqual(data2, ['a', 'b']) # must not change

data1 = (1, 2)
data2 = ('a', 'b')
self.assertEqual(operator.iconcat(data1, data2), (1, 2, 'a', 'b'))
self.assertEqual(operator.iconcat(data1, data2), data1 + data2)
self.assertEqual(data1, (1, 2)) # must not change
self.assertEqual(data2, ('a', 'b')) # must not change

data1 = '12'
data2 = 'ab'
self.assertEqual(operator.iconcat(data1, data2), '12ab')
self.assertEqual(operator.iconcat(data1, data2), data1 + data2)
self.assertEqual(data1, '12') # must not change
self.assertEqual(data2, 'ab') # must not change

# Subclasses:
class ListSubclass(list):
pass

data1 = ListSubclass([1, 2])
data2 = ListSubclass(['a', 'b'])
res = operator.iconcat(data1, data2)
self.assertIsInstance(res, ListSubclass)
self.assertEqual(res, [1, 2, 'a', 'b'])
self.assertIsInstance(data1, ListSubclass)
self.assertEqual(data1, ListSubclass([1, 2, 'a', 'b'])) # must change
self.assertIsInstance(data2, ListSubclass)
self.assertEqual(data2, ListSubclass(['a', 'b'])) # must not change

# Custom type with `__add__`:
class TupleSubclass(tuple):
def __add__(self, other):
return TupleSubclass(other + self)

data1 = TupleSubclass([1, 2])
data2 = ('a', 'b')
res = operator.iconcat(data1, data2)
self.assertIsInstance(res, TupleSubclass)
self.assertEqual(res, TupleSubclass(['a', 'b', 1, 2]))
self.assertIsInstance(data1, TupleSubclass)
self.assertEqual(data1, TupleSubclass([1, 2])) # must not change
self.assertIsInstance(data2, tuple)
self.assertEqual(data2, ('a', 'b')) # must not change

# Corner cases:
self.assertEqual(operator.iconcat([1, 2], []), [1, 2])
self.assertEqual(operator.iconcat([], [1, 2]), [1, 2])
self.assertEqual(operator.iconcat([], []), [])
self.assertEqual(operator.iconcat([], ()), [])

# Type errors:
self.assertRaises(TypeError, operator.iconcat, [], 1)
self.assertRaises(TypeError, operator.iconcat, 1, [])
self.assertRaises(TypeError, operator.iconcat, 1, 1)
self.assertRaises(TypeError, operator.iconcat, (), [])

# Returns `NotImplemented`:
class BrokenSeq1(list):
def __add__(self, other):
return NotImplemented
def __iadd__(self, other):
return NotImplemented

self.assertRaises(TypeError,
operator.iconcat, BrokenSeq1(), BrokenSeq1())

class BrokenSeq2(tuple):
def __add__(self, other):
return NotImplemented

self.assertRaises(TypeError,
operator.iconcat, BrokenSeq2(), BrokenSeq2())

def test_length_hint(self):
operator = self.module
class X(object):
Expand Down