Add error-code for truthy-function

[cdce8p]

Description

A separate error code for truthy-function so it can be enabled by default.

Closes #12621

[cdce8p]

@hauntsaninja Maybe this is something you're interested in? You expressed support for it in #12621 (comment).

[hauntsaninja]

That's a lot of primer hits; how many of them actually help users?

[cdce8p]

That's a lot of primer hits; how many of them actually help users?

Surprisingly many. Below the categories of primer errors I identified. IMO enabling it would be a net improvement. If it shouldn't be enabled by default however, I think we should still create a separate error code for it with truthy-function. truthy-bool does emit a lot of unnecessary noice in most projects.

True positives

Boolean of class

class SomeClass: ...

if SomeClass:
    ...

# or
assert SomeClass

sphinx (https://github.com/sphinx-doc/sphinx)
+ sphinx/util/requests.py:22:41: error: Function "Type[InsecureRequestWarning]" could always be true in boolean context  [truthy-function]

urllib3 (https://github.com/urllib3/urllib3)
+ src/urllib3/connectionpool.py:1027: error: Function "Type[HTTPSConnection]" could always be true in boolean context  [truthy-function]

artigraph (https://github.com/artigraph/artigraph)
+ tests/arti/test_thresholds.py:5: error: Function "Type[Threshold]" could always be true in boolean context  [truthy-function]

Boolean of function

def func: ...

if func:
    ...

# or
assert func

schema_salad (https://github.com/common-workflow-language/schema_salad)
+ schema_salad/tests/test_typescript_codegen.py:25:12: error: Function "Callable[[], bool]" could always be true in boolean context  [truthy-function]
+ schema_salad/tests/test_typescript_codegen.py:58:12: error: Function "Callable[[], bool]" could always be true in boolean context  [truthy-function]
+ schema_salad/tests/test_java_codegen.py:25:12: error: Function "Callable[[], bool]" could always be true in boolean context  [truthy-function]
+ schema_salad/tests/test_dotnet_codegen.py:25:12: error: Function "Callable[[], bool]" could always be true in boolean context  [truthy-function]
+ schema_salad/tests/test_dotnet_codegen.py:57:12: error: Function "Callable[[], bool]" could always be true in boolean context  [truthy-function]

dulwich (https://github.com/dulwich/dulwich)
+ dulwich/objects.py:980: error: Function "Callable[[Any], Any]" could always be true in boolean context

bandersnatch (https://github.com/pypa/bandersnatch)
+ src/bandersnatch/simple.py:251: error: Function "Callable[[], bool]" could always be true in boolean context

arviz (https://github.com/arviz-devs/arviz)
+ arviz/tests/base_tests/test_utils.py:250: error: Function "Callable[[Any, Any], Any]" could always be true in boolean context

Especially the assert func in tests can be quite useful. E.g. schema_salad has multiple instances of assert <Path>.exists instead of <Path>.exists().

Implicit optional

func: Callable = None
if func: ...

psycopg (https://github.com/psycopg/psycopg)
+ psycopg/psycopg/types/uuid.py:41: error: Function "Callable[..., UUID]" could always be true in boolean context  [truthy-function]
+ psycopg/psycopg/types/net.py:45: error: Function "Callable[[str], Union[IPv4Address, IPv6Address]]" could always be true in boolean context  [truthy-function]

tornado (https://github.com/tornadoweb/tornado)
+ tornado/simple_httpclient.py:550: error: Function "Callable[[HTTPResponse], None]" could always be true in boolean context

pydantic (https://github.com/samuelcolvin/pydantic)
+ pydantic/class_validators.py:263: error: Function "Callable[..., Any]" could always be true in boolean context  [truthy-function]

mongo-python-driver (https://github.com/mongodb/mongo-python-driver)
+ pymongo/monitor.py:433: error: Function "Callable[[], Any]" could always be true in boolean context  [truthy-function]
+ pymongo/monitor.py:436: error: Function "Callable[[], Any]" could always be true in boolean context  [truthy-function]

Some true positives

psycopg (https://github.com/psycopg/psycopg)
+ psycopg/psycopg/connection.py:338: error: Function "Callable[[ReferenceType[BaseConnection[Row]], PGresult], None]" could always be true in boolean context  [truthy-function]

If-check is for self._notice_handler which is a function, not self._notice_handlers a list.

--

sympy (https://github.com/sympy/sympy)
+ sympy/combinatorics/free_groups.py:96: error: Function "Type[Expr]" could always be true in boolean context

class A: ...
class B: ...

isinstance(var, A or B)

--

Tanjun (https://github.com/FasterSpeeding/Tanjun)
+ tanjun/hooks.py:45: error: Function "Type[TypeVar]" could always be true in boolean context  [truthy-function]

if TypeVar instead of the correct if TYPE_CHECKING.

--

+ homeassistant/helpers/schema_config_entry_flow.py:137: error: Function "Callable[[Dict[str, Any]], Optional[str]]" could always be true in boolean context  [truthy-function]
+ homeassistant/components/goodwe/number.py:131: error: Function "Callable[[Any, int], Awaitable[None]]" could always be true in boolean context  [truthy-function]
+ homeassistant/components/kostal_plenticore/sensor.py:178: error: Function "Callable[[str], Any]" could always be true in boolean context  [truthy-function]

I fixed these already: home-assistant/core#78819

False positives

There are also some false-positives, although those arguably need better typing or can't be fixed.

Import guard

try:
    from asyncio import create_task
except ImportError:  # Python < 3.7
    create_task = None  # type: ignore

if create_task:
    ...

graphql-core (https://github.com/graphql-python/graphql-core)
+ tests/test_user_registry.py:513: error: Function "Callable[[Union[Generator[Any, None, _T], Coroutine[Any, Any, _T]], DefaultNamedArg(Optional[str], 'name')], Task[_T]]" could always be true in boolean context

Moneypatching in tests

Deleting os.path.abspath, undoing it, and assert that function is present.

pytest (https://github.com/pytest-dev/pytest)
+ testing/test_monkeypatch.py:95: error: Function overloaded function could always be true in boolean context  [truthy-function]

[JelleZijlstra]

The Tanjun one was actually also wrong and just got fixed: FasterSpeeding/Tanjun@d697a6b

[hauntsaninja]

Thanks for the analysis! This looks pretty good to me. Will leave it open for a couple days in case anyone else has opinions.

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

sphinx (https://github.com/sphinx-doc/sphinx)
+ sphinx/util/rst.py: note: In function "default_role":
+ sphinx/util/rst.py:66:12: error: Function "Callable[[str, str, str, int, Inliner, Dict[str, Any], List[str]], Tuple[List[Node], List[system_message]]]" could always be true in boolean context  [truthy-function]
+ sphinx/directives/__init__.py: note: In member "run" of class "DefaultRole":
+ sphinx/directives/__init__.py:280:12: error: Function "Callable[[str, str, str, int, Inliner, Dict[str, Any], List[str]], Tuple[List[Node], List[system_message]]]" could always be true in boolean context  [truthy-function]
+ sphinx/writers/html5.py: note: In member "depart_math" of class "HTML5Translator":
+ sphinx/writers/html5.py:810:12: error: Function "Callable[..., Any]" could always be true in boolean context  [truthy-function]
+ sphinx/writers/html5.py: note: In member "depart_math_block" of class "HTML5Translator":
+ sphinx/writers/html5.py:821:12: error: Function "Callable[..., Any]" could always be true in boolean context  [truthy-function]
+ sphinx/writers/html.py: note: In member "depart_math" of class "HTMLTranslator":
+ sphinx/writers/html.py:872:12: error: Function "Callable[..., Any]" could always be true in boolean context  [truthy-function]
+ sphinx/writers/html.py: note: In member "depart_math_block" of class "HTMLTranslator":
+ sphinx/writers/html.py:883:12: error: Function "Callable[..., Any]" could always be true in boolean context  [truthy-function]
+ sphinx/util/requests.py: note: In function "ignore_insecure_warning":
+ sphinx/util/requests.py:22:41: error: Function "Type[InsecureRequestWarning]" could always be true in boolean context  [truthy-function]

graphql-core (https://github.com/graphql-python/graphql-core)
+ tests/test_user_registry.py:507: error: Function "Callable[[Union[Generator[Any, None, _T], Coroutine[Any, Any, _T]], DefaultNamedArg(Optional[str], 'name')], Task[_T]]" could always be true in boolean context  [truthy-function]

psycopg (https://github.com/psycopg/psycopg)
+ psycopg/psycopg/connection.py:338: error: Function "Callable[[ReferenceType[BaseConnection[Row]], PGresult], None]" could always be true in boolean context  [truthy-function]
+ psycopg/psycopg/types/uuid.py:41: error: Function "Callable[..., UUID]" could always be true in boolean context  [truthy-function]
+ psycopg/psycopg/types/net.py:45: error: Function "Callable[[str], Union[IPv4Address, IPv6Address]]" could always be true in boolean context  [truthy-function]

pyppeteer (https://github.com/pyppeteer/pyppeteer)
+ pyppeteer/browser.py:54: error: Function "Callable[[], Awaitable[None]]" could always be true in boolean context  [truthy-function]

urllib3 (https://github.com/urllib3/urllib3)
+ src/urllib3/connectionpool.py:1027: error: Function "Type[HTTPSConnection]" could always be true in boolean context  [truthy-function]
+ src/urllib3/connectionpool.py:1027: note: Error code "truthy-function" not covered by "type: ignore" comment

prefect (https://github.com/PrefectHQ/prefect)
+ src/prefect/settings.py:667: error: Function "Callable[[Settings, T], T]" could always be true in boolean context  [truthy-function]
+ src/prefect/engine.py:1186: error: Function "Callable[[TaskRunContext, Dict[str, Any]], Optional[str]]" could always be true in boolean context  [truthy-function]

artigraph (https://github.com/artigraph/artigraph)
+ tests/arti/test_thresholds.py:5: error: Function "Type[Threshold]" could always be true in boolean context  [truthy-function]

sympy (https://github.com/sympy/sympy)
+ sympy/combinatorics/free_groups.py:96: error: Function "Type[Expr]" could always be true in boolean context  [truthy-function]

dulwich (https://github.com/dulwich/dulwich)
+ dulwich/objects.py:980: error: Function "Callable[[Any], Any]" could always be true in boolean context  [truthy-function]

schema_salad (https://github.com/common-workflow-language/schema_salad)
+ schema_salad/tests/test_typescript_codegen.py: note: In function "test_cwl_gen":
+ schema_salad/tests/test_typescript_codegen.py:25:12: error: Function "Callable[[], bool]" could always be true in boolean context  [truthy-function]
+ schema_salad/tests/test_typescript_codegen.py: note: In function "test_class_field":
+ schema_salad/tests/test_typescript_codegen.py:58:12: error: Function "Callable[[], bool]" could always be true in boolean context  [truthy-function]
+ schema_salad/tests/test_java_codegen.py: note: In function "test_cwl_gen":
+ schema_salad/tests/test_java_codegen.py:25:12: error: Function "Callable[[], bool]" could always be true in boolean context  [truthy-function]
+ schema_salad/tests/test_dotnet_codegen.py: note: In function "test_cwl_gen":
+ schema_salad/tests/test_dotnet_codegen.py:25:12: error: Function "Callable[[], bool]" could always be true in boolean context  [truthy-function]
+ schema_salad/tests/test_dotnet_codegen.py: note: In function "test_class_field":
+ schema_salad/tests/test_dotnet_codegen.py:57:12: error: Function "Callable[[], bool]" could always be true in boolean context  [truthy-function]

arviz (https://github.com/arviz-devs/arviz)
+ arviz/tests/base_tests/test_utils.py:250: error: Function "Callable[[Any, Any], Any]" could always be true in boolean context  [truthy-function]

tornado (https://github.com/tornadoweb/tornado)
+ tornado/simple_httpclient.py:550: error: Function "Callable[[HTTPResponse], None]" could always be true in boolean context  [truthy-function]

pydantic (https://github.com/samuelcolvin/pydantic)
+ pydantic/class_validators.py:263: error: Function "Callable[..., Any]" could always be true in boolean context  [truthy-function]

pytest (https://github.com/pytest-dev/pytest)
+ testing/test_monkeypatch.py:95: error: Function overloaded function could always be true in boolean context  [truthy-function]

core (https://github.com/home-assistant/core)
+ homeassistant/components/radarr/sensor.py:167: error: Function "Callable[[RadarrSensorEntityDescription[Any], Any], Optional[Tuple[RadarrSensorEntityDescription[Any], str]]]" could always be true in boolean context  [truthy-function]
+ homeassistant/components/lidarr/sensor.py:123: error: Function "Callable[[LidarrSensorEntityDescription[Any], Any], Optional[Tuple[LidarrSensorEntityDescription[Any], str]]]" could always be true in boolean context  [truthy-function]

cloud-init (https://github.com/canonical/cloud-init)
+ cloudinit/url_helper.py:654: error: Function "Callable[[Any, int], int]" could always be true in boolean context  [truthy-function]

mongo-python-driver (https://github.com/mongodb/mongo-python-driver)
+ pymongo/monitor.py: note: In function "_shutdown_resources":
+ pymongo/monitor.py:433: error: Function "Callable[[], Any]" could always be true in boolean context  [truthy-function]
+ pymongo/monitor.py:436: error: Function "Callable[[], Any]" could always be true in boolean context  [truthy-function]

[sobolevn]

dulwich has this line: https://github.com/jelmer/dulwich/blob/master/dulwich/objects.py#L980

key_func = name_order and key_entry_name_order or key_entry

I am pretty sure that it is an example of old-style ternary. This rule does not like it.
Probably, this is a good thing. But, I thought it is worth highlighting.

[cdce8p]

dullwitch has this line: https://github.com/jelmer/dulwich/blob/master/dulwich/objects.py#L980

key_func = name_order and key_entry_name_order or key_entry

I am pretty sure that it is an example of old-style ternary. This rule does not like it. Probably, this is a good thing. But, I thought it is worth highlighting.

Not sure we can do anything about it. I would probably use a type: ignore in this case.

[andersk]

Should be under “enabled by default” rather than “optional checks”, right?

• Move truthy-function docs from “optional checks” to “enabled by default” #14380