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blind-except (BLE001) is not active at all #16767

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dolfandringa opened this issue Mar 15, 2025 · 2 comments
Closed

blind-except (BLE001) is not active at all #16767

dolfandringa opened this issue Mar 15, 2025 · 2 comments
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documentation Improvements or additions to documentation question Asking for support or clarification

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@dolfandringa
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dolfandringa commented Mar 15, 2025 •
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Summary

According to the docs, blind-except (BLE001) says that except Exception is bad, which I agree with. But it looks like ruff by default doesn't actually check for blind-except at all. Is this intentional? If there are errors that ruff does not check for by default, it would make sense to me to document with those errors, that they are off by default.

This test.py file does not get flagged by ruff as being invalid.

a = 1
b = 0
try:
    print(a / b)
except Exception as e:
    print(e)

try:
    print(a / b)
except Exception:
    print("error")

try:
    print(a / b)
except BaseException:
    print("error2")

❯ ruff --version
ruff 0.11.0
❯ ruff check test.py
All checks passed!

While if I turn it into this:

a = 1
b = 0
try:
    print(a / b)
except Exception as e:
    print(e)

try:
    print(a / b)
except Exception:
    print("error")

try:
    print(a / b)
except:
    pass

it does get flagged as a bare except:

❯ ruff check test.py
test.py:15:1: E722 Do not use bare `except`
   |
13 | try:
14 |     print(a / b)
15 | except:
   | ^^^^^^ E722
16 |     pass
   |

Found 1 error.

And running ruff with selecting BLE001 explicitely also flags it:

❯ ruff check test.py --select BLE001
test.py:5:8: BLE001 Do not catch blind exception: `Exception`
  |
3 | try:
4 |     print(a / b)
5 | except Exception as e:
  |        ^^^^^^^^^ BLE001
6 |     print(e)
  |

test.py:10:8: BLE001 Do not catch blind exception: `BaseException`
   |
 8 | try:
 9 |     print(a / b)
10 | except BaseException:
   |        ^^^^^^^^^^^^^ BLE001
11 |     print("error")
   |

Found 2 errors.

Version

0.3.7 and 0.11.0
@dolfandringa dolfandringa changed the title blind-except (BLE001) false negative with except Exception blind-except (BLE001) is not active at all Mar 15, 2025
@dolfandringa
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Ok, this is as intended. I am just surprised this is not on by default. Also, i think it makes sense to document what rules are on by default with the rules. Now it's really tedious to search through the default config and then the list of rules what is and isn't on by default. But that's a different issue.

@ntBre
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ntBre commented Mar 15, 2025

Only a pretty small set of rules is enabled by default. See the rule documentation:

By default, Ruff enables Flake8's F rules, along with a subset of the E rules, omitting any stylistic rules that overlap with the use of a formatter, like ruff format or Black.

You can also run ruff check --show-settings and look for the linter.rules_enabled section. That shows all of the enabled rules with their names and codes.

I think some people also like to use the special ALL rule code to select all rules and then ignore the ones they don't want. If you want to enable a large number of rules, that could be easier than selecting them all.

Maybe it would be nice if we added an icon for default rules in the main rules page, though.

@ntBre ntBre added documentation Improvements or additions to documentation question Asking for support or clarification labels Mar 15, 2025
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