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hauntsaninja merged 3 commits into from
Mar 29, 2023
Merged

Improve bytes formatting error #14959

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Improve bytes formatting error
hauntsaninja Mar 26, 2023
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hauntsaninja Mar 26, 2023
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hauntsaninja Mar 26, 2023
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11 changes: 5 additions & 6 deletions mypy/checkstrformat.py
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Original file line number Diff line number Diff line change
Expand Up @@ -435,9 +435,9 @@ def perform_special_format_checks(
actual_type, "__str__"
):
self.msg.fail(
'On Python 3 formatting "b\'abc\'" with "{}" '
'produces "b\'abc\'", not "abc"; '
'use "{!r}" if this is desired behavior',
'If x = b\'abc\' then f"{x}" or "{}".format(x) produces "b\'abc\'", '
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@sobolevn sobolevn Mar 26, 2023

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Sadly, we have no way of telling whether it is a .format call or fstring. It would really help with the error message.

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@JelleZijlstra JelleZijlstra Mar 27, 2023

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Is that because we desugar f-strings into a CallExpr that looks just like a str.format call? Maybe we can stash some data in the CallExpr to indicate that it derived from an f-string.

'not "abc". If this is desired behavior, use f"{x!r}" or "{!r}".format(x). '
"Otherwise, decode the bytes",
call,
code=codes.STR_BYTES_PY3,
)
Expand Down Expand Up @@ -946,9 +946,8 @@ def check_s_special_cases(self, expr: FormatStringExpr, typ: Type, context: Cont
# Couple special cases for string formatting.
if has_type_component(typ, "builtins.bytes"):
self.msg.fail(
'On Python 3 formatting "b\'abc\'" with "%s" '
'produces "b\'abc\'", not "abc"; '
'use "%r" if this is desired behavior',
'If x = b\'abc\' then "%s" % x produces "b\'abc\'", not "abc". '
'If this is desired behavior use "%r" % x. Otherwise, decode the bytes',
context,
code=codes.STR_BYTES_PY3,
)
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3 changes: 1 addition & 2 deletions mypyc/test-data/run-strings.test
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Expand Up @@ -232,8 +232,7 @@ def test_fstring_basics() -> None:

x = bytes([1, 2, 3, 4])
# assert f'bytes: {x}' == "bytes: b'\\x01\\x02\\x03\\x04'"
# error: On Python 3 formatting "b'abc'" with "{}" produces "b'abc'", not "abc";
# use "{!r}" if this is desired behavior behavior
# error: If x = b'abc' then f"{x}" or "{}".format(x) produces "b'abc'", not "abc". If this is desired behavior, use f"{x!r}" or "{!r}".format(x). Otherwise, decode the bytes

float_num = 123.4
assert f'{float_num}' == '123.4'
Expand Down
4 changes: 2 additions & 2 deletions test-data/unit/check-errorcodes.test
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Expand Up @@ -638,8 +638,8 @@ def g() -> int:
'%d' % 'no' # E: Incompatible types in string interpolation (expression has type "str", placeholder has type "Union[int, float, SupportsInt]") [str-format]
'%d + %d' % (1, 2, 3) # E: Not all arguments converted during string formatting [str-format]

'{}'.format(b'abc') # E: On Python 3 formatting "b'abc'" with "{}" produces "b'abc'", not "abc"; use "{!r}" if this is desired behavior [str-bytes-safe]
'%s' % b'abc' # E: On Python 3 formatting "b'abc'" with "%s" produces "b'abc'", not "abc"; use "%r" if this is desired behavior [str-bytes-safe]
'{}'.format(b'abc') # E: If x = b'abc' then f"{x}" or "{}".format(x) produces "b'abc'", not "abc". If this is desired behavior, use f"{x!r}" or "{!r}".format(x). Otherwise, decode the bytes [str-bytes-safe]
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@sobolevn sobolevn Mar 26, 2023

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What do you think about injecting real user's values into the error message?

'%s' % b'abc' # E: If x = b'abc' then "%s" % x produces "b'abc'", not "abc". If this is desired behavior use "%r" % x. Otherwise, decode the bytes [str-bytes-safe]
[builtins fixtures/primitives.pyi]
[typing fixtures/typing-medium.pyi]

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20 changes: 10 additions & 10 deletions test-data/unit/check-formatting.test
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Expand Up @@ -30,8 +30,8 @@ xb: bytes
xs: str

'%s' % xs # OK
'%s' % xb # E: On Python 3 formatting "b'abc'" with "%s" produces "b'abc'", not "abc"; use "%r" if this is desired behavior
'%(name)s' % {'name': b'value'} # E: On Python 3 formatting "b'abc'" with "%s" produces "b'abc'", not "abc"; use "%r" if this is desired behavior
'%s' % xb # E: If x = b'abc' then "%s" % x produces "b'abc'", not "abc". If this is desired behavior use "%r" % x. Otherwise, decode the bytes
'%(name)s' % {'name': b'value'} # E: If x = b'abc' then "%s" % x produces "b'abc'", not "abc". If this is desired behavior use "%r" % x. Otherwise, decode the bytes
[builtins fixtures/primitives.pyi]

[case testStringInterpolationCount]
Expand Down Expand Up @@ -435,21 +435,21 @@ N = NewType('N', bytes)
n: N

'{}'.format(a)
'{}'.format(b) # E: On Python 3 formatting "b'abc'" with "{}" produces "b'abc'", not "abc"; use "{!r}" if this is desired behavior
'{}'.format(x) # E: On Python 3 formatting "b'abc'" with "{}" produces "b'abc'", not "abc"; use "{!r}" if this is desired behavior
'{}'.format(n) # E: On Python 3 formatting "b'abc'" with "{}" produces "b'abc'", not "abc"; use "{!r}" if this is desired behavior
'{}'.format(b) # E: If x = b'abc' then f"{x}" or "{}".format(x) produces "b'abc'", not "abc". If this is desired behavior, use f"{x!r}" or "{!r}".format(x). Otherwise, decode the bytes
'{}'.format(x) # E: If x = b'abc' then f"{x}" or "{}".format(x) produces "b'abc'", not "abc". If this is desired behavior, use f"{x!r}" or "{!r}".format(x). Otherwise, decode the bytes
'{}'.format(n) # E: If x = b'abc' then f"{x}" or "{}".format(x) produces "b'abc'", not "abc". If this is desired behavior, use f"{x!r}" or "{!r}".format(x). Otherwise, decode the bytes

f'{b}' # E: On Python 3 formatting "b'abc'" with "{}" produces "b'abc'", not "abc"; use "{!r}" if this is desired behavior
f'{x}' # E: On Python 3 formatting "b'abc'" with "{}" produces "b'abc'", not "abc"; use "{!r}" if this is desired behavior
f'{n}' # E: On Python 3 formatting "b'abc'" with "{}" produces "b'abc'", not "abc"; use "{!r}" if this is desired behavior
f'{b}' # E: If x = b'abc' then f"{x}" or "{}".format(x) produces "b'abc'", not "abc". If this is desired behavior, use f"{x!r}" or "{!r}".format(x). Otherwise, decode the bytes
f'{x}' # E: If x = b'abc' then f"{x}" or "{}".format(x) produces "b'abc'", not "abc". If this is desired behavior, use f"{x!r}" or "{!r}".format(x). Otherwise, decode the bytes
f'{n}' # E: If x = b'abc' then f"{x}" or "{}".format(x) produces "b'abc'", not "abc". If this is desired behavior, use f"{x!r}" or "{!r}".format(x). Otherwise, decode the bytes

class C(Generic[B]):
x: B
def meth(self) -> None:
'{}'.format(self.x) # E: On Python 3 formatting "b'abc'" with "{}" produces "b'abc'", not "abc"; use "{!r}" if this is desired behavior
'{}'.format(self.x) # E: If x = b'abc' then f"{x}" or "{}".format(x) produces "b'abc'", not "abc". If this is desired behavior, use f"{x!r}" or "{!r}".format(x). Otherwise, decode the bytes

def func(x: A) -> A:
'{}'.format(x) # E: On Python 3 formatting "b'abc'" with "{}" produces "b'abc'", not "abc"; use "{!r}" if this is desired behavior
'{}'.format(x) # E: If x = b'abc' then f"{x}" or "{}".format(x) produces "b'abc'", not "abc". If this is desired behavior, use f"{x!r}" or "{!r}".format(x). Otherwise, decode the bytes
return x

'{!r}'.format(a)
Expand Down
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