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Add singleton escape hatch to B008 documentation #8501

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Nov 7, 2023
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Add singleton escape hatch to B008 documentation #8501

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14 changes: 12 additions & 2 deletions crates/ruff_linter/src/rules/flake8_bugbear/rules/function_call_in_argument_default.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,16 @@ use crate::checkers::ast::Checker;
/// return arg
/// ```
///
/// If the use of a singleton is intentional, assign the result call to a
/// module-level variable, and use that variable in the default argument:
/// ```python
/// ERROR = ValueError("Hosts weren't successfully added")
///
///
/// def add_host(error: Exception = ERROR) -> None:
/// ...
/// ```
///
/// ## Options
/// - `flake8-bugbear.extend-immutable-calls`
#[violation]
Expand All @@ -62,9 +72,9 @@ impl Violation for FunctionCallInDefaultArgument {
fn message(&self) -> String {
let FunctionCallInDefaultArgument { name } = self;
if let Some(name) = name {
format!("Do not perform function call `{name}` in argument defaults")
format!("Do not perform function call `{name}` in argument defaults; instead, perform the call within the function, or read the default from a module-level singleton variable")
} else {
format!("Do not perform function call in argument defaults")
format!("Do not perform function call in argument defaults; instead, perform the call within the function, or read the default from a module-level singleton variable")
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I'm not a huge fan of bugbear's error messages which tend to be very long (https://github.com/PyCQA/flake8-bugbear/blob/907e0dd29a99818591a604d4557c70ea33204712/bugbear.py#L1660-L1667). I prefer to put that level of detail in our documentation, or make it evident via the proposed fix. But I do think this one can be a bit clearer. Wdyt @zanieb?

}
}
}
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20 changes: 10 additions & 10 deletions ...lake8_bugbear/snapshots/ruff_linter__rules__flake8_bugbear__tests__B008_B006_B008.py.snap
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Original file line number Diff line number Diff line change
@@ -1,29 +1,29 @@
---
source: crates/ruff_linter/src/rules/flake8_bugbear/mod.rs
---
B006_B008.py:102:61: B008 Do not perform function call `range` in argument defaults
B006_B008.py:102:61: B008 Do not perform function call `range` in argument defaults; instead, perform the call within the function, or read the default from a module-level singleton variable
|
101 | # N.B. we're also flagging the function call in the comprehension
102 | def list_comprehension_also_not_okay(default=[i**2 for i in range(3)]):
| ^^^^^^^^ B008
103 | pass
|

B006_B008.py:106:64: B008 Do not perform function call `range` in argument defaults
B006_B008.py:106:64: B008 Do not perform function call `range` in argument defaults; instead, perform the call within the function, or read the default from a module-level singleton variable
|
106 | def dict_comprehension_also_not_okay(default={i: i**2 for i in range(3)}):
| ^^^^^^^^ B008
107 | pass
|

B006_B008.py:110:60: B008 Do not perform function call `range` in argument defaults
B006_B008.py:110:60: B008 Do not perform function call `range` in argument defaults; instead, perform the call within the function, or read the default from a module-level singleton variable
|
110 | def set_comprehension_also_not_okay(default={i**2 for i in range(3)}):
| ^^^^^^^^ B008
111 | pass
|

B006_B008.py:126:39: B008 Do not perform function call `time.time` in argument defaults
B006_B008.py:126:39: B008 Do not perform function call `time.time` in argument defaults; instead, perform the call within the function, or read the default from a module-level singleton variable
|
124 | # B008
125 | # Flag function calls as default args (including if they are part of a sub-expression)
Expand All @@ -32,21 +32,21 @@ B006_B008.py:126:39: B008 Do not perform function call `time.time` in argument d
127 | ...
|

B006_B008.py:130:12: B008 Do not perform function call `dt.datetime.now` in argument defaults
B006_B008.py:130:12: B008 Do not perform function call `dt.datetime.now` in argument defaults; instead, perform the call within the function, or read the default from a module-level singleton variable
|
130 | def f(when=dt.datetime.now() + dt.timedelta(days=7)):
| ^^^^^^^^^^^^^^^^^ B008
131 | pass
|

B006_B008.py:134:30: B008 Do not perform function call in argument defaults
B006_B008.py:134:30: B008 Do not perform function call in argument defaults; instead, perform the call within the function, or read the default from a module-level singleton variable
|
134 | def can_even_catch_lambdas(a=(lambda x: x)()):
| ^^^^^^^^^^^^^^^ B008
135 | ...
|

B006_B008.py:239:31: B008 Do not perform function call `dt.datetime.now` in argument defaults
B006_B008.py:239:31: B008 Do not perform function call `dt.datetime.now` in argument defaults; instead, perform the call within the function, or read the default from a module-level singleton variable
|
237 | # B006 and B008
238 | # We should handle arbitrary nesting of these B008.
Expand All @@ -55,7 +55,7 @@ B006_B008.py:239:31: B008 Do not perform function call `dt.datetime.now` in argu
240 | pass
|

B006_B008.py:245:22: B008 Do not perform function call `map` in argument defaults
B006_B008.py:245:22: B008 Do not perform function call `map` in argument defaults; instead, perform the call within the function, or read the default from a module-level singleton variable
|
243 | # Don't flag nested B006 since we can't guarantee that
244 | # it isn't made mutable by the outer operation.
Expand All @@ -64,15 +64,15 @@ B006_B008.py:245:22: B008 Do not perform function call `map` in argument default
246 | pass
|

B006_B008.py:250:19: B008 Do not perform function call `random.randint` in argument defaults
B006_B008.py:250:19: B008 Do not perform function call `random.randint` in argument defaults; instead, perform the call within the function, or read the default from a module-level singleton variable
|
249 | # B008-ception.
250 | def nested_b008(a=random.randint(0, dt.datetime.now().year)):
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ B008
251 | pass
|

B006_B008.py:250:37: B008 Do not perform function call `dt.datetime.now` in argument defaults
B006_B008.py:250:37: B008 Do not perform function call `dt.datetime.now` in argument defaults; instead, perform the call within the function, or read the default from a module-level singleton variable
|
249 | # B008-ception.
250 | def nested_b008(a=random.randint(0, dt.datetime.now().year)):
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2 changes: 1 addition & 1 deletion ...pshots/ruff_linter__rules__flake8_bugbear__tests__extend_immutable_calls_arg_default.snap
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@@ -1,7 +1,7 @@
---
source: crates/ruff_linter/src/rules/flake8_bugbear/mod.rs
---
B008_extended.py:24:51: B008 Do not perform function call `Depends` in argument defaults
B008_extended.py:24:51: B008 Do not perform function call `Depends` in argument defaults; instead, perform the call within the function, or read the default from a module-level singleton variable
|
24 | def error_due_to_missing_import(data: List[str] = Depends(None)):
| ^^^^^^^^^^^^^ B008
Expand Down