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[flake8-return] Recognize functions returning Never as non-returning (RET503) #15298

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Jan 7, 2025
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[flake8-return] Recognize functions returning Never as non-returning (RET503) #15298

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bcd639c
[`flake8-return`] Recognize functions returning `Never` as non-return…
viccie30 Jan 6, 2025
fc2bac8
Avoid redeclarations in test files, inline nested function test case …
MichaReiser Jan 7, 2025
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60 changes: 50 additions & 10 deletions crates/ruff_linter/resources/test/fixtures/flake8_return/RET503.py
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Original file line number Diff line number Diff line change
Expand Up @@ -331,17 +331,16 @@ def end_of_file():


# function return type annotation NoReturn
def bar_no_return_annotation() -> NoReturn:
abort()

def foo(x: int) -> int:
def bar() -> NoReturn:
abort()
if x == 5:
return 5
bar()
bar_no_return_annotation()


def foo(string: str) -> str:
def raises(value: str) -> NoReturn:
raise RuntimeError("something went wrong")

match string:
case "a":
Expand All @@ -351,23 +350,49 @@ def raises(value: str) -> NoReturn:
case "c":
return "third"
case _:
raises(string)
bar_no_return_annotation()


def foo() -> int:
def baz() -> int:
return 1

if baz() > 3:
return 1
bar_no_return_annotation()

def bar() -> NoReturn:
a = 1 + 2
raise AssertionError("Very bad")


# function return type annotation typing_extensions.Never
def bar_never_annotation() -> typing_extensions.Never:
abort()

def foo(x: int) -> int:
if x == 5:
return 5
bar_never_annotation()


def foo(string: str) -> str:

match string:
case "a":
return "first"
case "b":
return "second"
case "c":
return "third"
case _:
bar_never_annotation()


def foo() -> int:
def baz() -> int:
return 1

if baz() > 3:
return 1
bar()
bar_never_annotation()


def f():
Expand All @@ -376,3 +401,18 @@ def f():
else:
with c:
d



# The rule shouldn't generate a diagnostic for functions where one branch
# calls a nested function annotated with `NoReturn` or `Never`.
# However, the rule isn't handling this case correctly yet.
# This is because looking up `bar` fails when analysing `foo` because
# the semantic model hasn't yet seen `bar`'s declaration.
# Supporting nested functions requires making this a deferred rule.
def foo(x: int) -> int:
def bar() -> NoReturn:
abort()
if x == 5:
return 5
bar()
1 change: 1 addition & 0 deletions crates/ruff_linter/src/rules/flake8_return/rules/function.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -450,6 +450,7 @@ fn is_noreturn_func(func: &Expr, semantic: &SemanticModel) -> bool {
};

semantic.match_typing_qualified_name(&qualified_name, "NoReturn")
|| semantic.match_typing_qualified_name(&qualified_name, "Never")
}

fn add_return_none(checker: &mut Checker, stmt: &Stmt, range: TextRange) {
Expand Down
82 changes: 24 additions & 58 deletions ...s/flake8_return/snapshots/ruff_linter__rules__flake8_return__tests__RET503_RET503.py.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -403,71 +403,37 @@ RET503.py:329:5: RET503 [*] Missing explicit `return` at the end of function abl
332 333 |
333 334 | # function return type annotation NoReturn

RET503.py:339:5: RET503 [*] Missing explicit `return` at the end of function able to return non-`None` value
RET503.py:403:13: RET503 [*] Missing explicit `return` at the end of function able to return non-`None` value
|
337 | if x == 5:
338 | return 5
339 | bar()
| ^^^^^ RET503
|
= help: Add explicit `return` statement

ℹ Unsafe fix
337 337 | if x == 5:
338 338 | return 5
339 339 | bar()
340 |+ return None
340 341 |
341 342 |
342 343 | def foo(string: str) -> str:

RET503.py:354:13: RET503 [*] Missing explicit `return` at the end of function able to return non-`None` value
|
352 | return "third"
353 | case _:
354 | raises(string)
| ^^^^^^^^^^^^^^ RET503
401 | else:
402 | with c:
403 | d
| ^ RET503
|
= help: Add explicit `return` statement

ℹ Unsafe fix
352 352 | return "third"
353 353 | case _:
354 354 | raises(string)
355 |+ return None
355 356 |
356 357 |
357 358 | def foo() -> int:

RET503.py:370:5: RET503 [*] Missing explicit `return` at the end of function able to return non-`None` value
|
368 | if baz() > 3:
369 | return 1
370 | bar()
401 401 | else:
402 402 | with c:
403 403 | d
404 |+ return None
404 405 |
405 406 |
406 407 |

RET503.py:418:5: RET503 [*] Missing explicit `return` at the end of function able to return non-`None` value
|
416 | if x == 5:
417 | return 5
418 | bar()
| ^^^^^ RET503
|
= help: Add explicit `return` statement

ℹ Unsafe fix
368 368 | if baz() > 3:
369 369 | return 1
370 370 | bar()
371 |+ return None
371 372 |
372 373 |
373 374 | def f():

RET503.py:378:13: RET503 [*] Missing explicit `return` at the end of function able to return non-`None` value
|
376 | else:
377 | with c:
378 | d
| ^ RET503
|
= help: Add explicit `return` statement

ℹ Unsafe fix
376 376 | else:
377 377 | with c:
378 378 | d
379 |+ return None
415 415 | abort()
416 416 | if x == 5:
417 417 | return 5
418 |- bar()
418 |+ bar()
419 |+ return None
120 changes: 33 additions & 87 deletions ...return/snapshots/ruff_linter__rules__flake8_return__tests__preview__RET503_RET503.py.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -411,99 +411,45 @@ RET503.py:326:1: RET503 [*] Missing explicit `return` at the end of function abl
332 333 |
333 334 | # function return type annotation NoReturn

RET503.py:334:1: RET503 [*] Missing explicit `return` at the end of function able to return non-`None` value
|
333 | # function return type annotation NoReturn
334 | / def foo(x: int) -> int:
335 | | def bar() -> NoReturn:
336 | | abort()
337 | | if x == 5:
338 | | return 5
339 | | bar()
| |_________^ RET503
|
= help: Add explicit `return` statement

ℹ Unsafe fix
337 337 | if x == 5:
338 338 | return 5
339 339 | bar()
340 |+ return None
340 341 |
341 342 |
342 343 | def foo(string: str) -> str:

RET503.py:342:1: RET503 [*] Missing explicit `return` at the end of function able to return non-`None` value
|
342 | / def foo(string: str) -> str:
343 | | def raises(value: str) -> NoReturn:
344 | | raise RuntimeError("something went wrong")
345 | |
346 | | match string:
347 | | case "a":
348 | | return "first"
349 | | case "b":
350 | | return "second"
351 | | case "c":
352 | | return "third"
353 | | case _:
354 | | raises(string)
| |__________________________^ RET503
RET503.py:398:1: RET503 [*] Missing explicit `return` at the end of function able to return non-`None` value
|
398 | / def f():
399 | | if a:
400 | | return b
401 | | else:
402 | | with c:
403 | | d
| |_____________^ RET503
|
= help: Add explicit `return` statement

ℹ Unsafe fix
352 352 | return "third"
353 353 | case _:
354 354 | raises(string)
355 |+ return None
355 356 |
356 357 |
357 358 | def foo() -> int:

RET503.py:357:1: RET503 [*] Missing explicit `return` at the end of function able to return non-`None` value
|
357 | / def foo() -> int:
358 | | def baz() -> int:
359 | | return 1
360 | |
361 | |
362 | | def bar() -> NoReturn:
363 | | a = 1 + 2
364 | | raise AssertionError("Very bad")
365 | |
366 | |
367 | |
368 | | if baz() > 3:
369 | | return 1
370 | | bar()
401 401 | else:
402 402 | with c:
403 403 | d
404 |+ return None
404 405 |
405 406 |
406 407 |

RET503.py:413:1: RET503 [*] Missing explicit `return` at the end of function able to return non-`None` value
|
411 | # the semantic model hasn't yet seen `bar`'s declaration.
412 | # Supporting nested functions requires making this a deferred rule.
413 | / def foo(x: int) -> int:
414 | | def bar() -> NoReturn:
415 | | abort()
416 | | if x == 5:
417 | | return 5
418 | | bar()
| |_________^ RET503
|
= help: Add explicit `return` statement

ℹ Unsafe fix
368 368 | if baz() > 3:
369 369 | return 1
370 370 | bar()
371 |+ return None
371 372 |
372 373 |
373 374 | def f():

RET503.py:373:1: RET503 [*] Missing explicit `return` at the end of function able to return non-`None` value
|
373 | / def f():
374 | | if a:
375 | | return b
376 | | else:
377 | | with c:
378 | | d
| |_____________^ RET503
|
= help: Add explicit `return` statement

ℹ Unsafe fix
376 376 | else:
377 377 | with c:
378 378 | d
379 |+ return None
415 415 | abort()
416 416 | if x == 5:
417 417 | return 5
418 |- bar()
418 |+ bar()
419 |+ return None
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