ruff RUF050

labelled unknown

Runs / 2026-10-17T21-46-31-989Z-5jx5-ruff-RUF050ruff 0.17.12026-10-17 21:46 UTC8 programs × 2 round(s)16 programs, 7 fired, 7 fixed, 0 findings, 1 rejectedmodel cost $0.0047

Analysis Nemotron 3 Super

Flags standalone 'if' statements whose bodies contain only 'pass' or ellipsis ('...').

Fix: Removes the entire 'if' statement if its condition is side-effect-free; otherwise replaces it with the condition as an expression statement.

8 hazards

Rewrite drops inline or trailing comments attached to the 'if' line or indented block, altering source documentation.
If the condition is a name like 'if x:', the fix treats it as side-effect-free and removes it, but 'x.__bool__()' might have side effects if overridden, changing behavior.
When the condition has side effects (e.g., a function call), replacing 'if func(): pass' with 'func()' evaluates the condition once instead of potentially short-circuiting in larger contexts, though here it's standalone so evaluation count remains one—still, if the call was relied upon for truthiness in a now-removed branch, logic may mislead readers.
In nested scopes, removing an 'if' block could inadvertently expose variables meant to be conditionally scoped (though Python lacks block scope, this affects readability and potential accidental reuse).
If the 'if' statement is the only thing in a module or block, removing it may create an unexpected blank line or affect formatting-dependent tools.
The fix may interfere with source‑generation tools that rely on the presence of syntactic scaffolding (like code‑generation templates) even when the body is a no‑op.
If the ellipsis '...' is used intentionally as a stub (e.g., in API skeletons), removing the 'if' could delete a meaningful placeholder despite being semantically empty.
When the condition involves chained comparisons or complex expressions, extracting it as a standalone statement may hinder debugging (e.g., breakpoint placement on the 'if' line vs. the expression line).

Programs

id	result	title	hazard
r1-p001	fix ok	star-imports-module-side-effects-all	star-imports, module-level side effects, __all__
r1-p002	fix ok	file-modes-truncation-partial-write-nonstr-data	file modes and truncation, partial writes, non-str data passed to write
r1-p003	fix ok	only-statement-in-blank-line-formatting-tools	If the 'if' statement is the only thing in a module or block, removing it may create an unexpected blank line or affect formatting-dependent tools.
r1-p004	fix ok	ellipsis-as-intentional-stub-api-skeleton	If the ellipsis '...' is used intentionally as a stub (e.g., in API skeletons), removing the 'if' could delete a meaningful placeholder despite being semantically empty.
r1-p005	fix ok	keyword-only-positional-only-args-kwargs-forwarding-defaults-evaluated-once	keyword-only, positional-only, args/*kwargs forwarding, defaults evaluated once
r1-p006	silent prediction off	async-def-await-ordering-async-generators	async def/await ordering, async generators
r1-p007	fix ok	mutable-default-arguments-aliasing-after-rewrite	mutable default arguments and aliasing after a rewrite
r1-p008	fix ok	truthiness-custom-bool-len-none-falsy-is-vs-equals	truthiness of custom __bool__/__len__, None vs falsy, 'is' vs '=='
r2-p001	silent prediction off	Evaluation Order Side Effects - Merged/Duplicated Condition	Rule merges duplicate conditions without preserving evaluation order or intermediate side effects.
r2-p002	silent prediction off	Source Generation Scaffolding Dependency	Removing empty if blocks breaks template-based code generation that relies on structural markers.
r2-p003	silent prediction off	Name Condition Overridden __bool__ Side Effect	Treating 'if x:' as side-effect-free ignores x.__bool__() which may mutate state.
r2-p004	silent prediction off	Comment Stripping Alters Documentation	Fix removes inline/trailing comments on if line or in block, losing developer intent.
r2-p005	invalid	Iterator Consumption in Condition	Duplicating condition expression consumes iterator twice when it should be once.
r2-p006	silent prediction off	Chained Comparison Hinders Debugging	Extracting chained comparison as expression stmt breaks breakpoint utility on original if line.
r2-p007	silent prediction off	Numeric Coercion Edge Case with Division	Fix alters timing/evaluation of numeric expressions involving coercion or rounding.
r2-p008	silent prediction off	F-string Repr/Src in Condition with Nested Quotes	Condition expression contains f-string with nested quotes; duplication risks quote instability.

Sources

r1-p001 · star-imports-module-side-effects-all

1~~__all__ = ['x']~~

2~~x = 1~~

3from mod import *

4~~if False:~~

5 ~~...~~

6~~print(x)~~

--- orig.py	2026-10-17 17:46:44.048674043 -0400
+++ fixed.py	2026-10-17 17:46:44.457761697 -0400
@@ -1,6 +1,4 @@
 __all__ = ['x']
 x = 1
 from mod import *
-if False:
-    ...
 print(x)

r1-p002 · file-modes-truncation-partial-write-nonstr-data

1~~with open('tmp.txt', 'w') as f:~~

2 ~~f.write(b'abc')~~

3~~if 0:~~

4 ~~pass~~

5~~with open('tmp.txt', 'r') as f:~~

6 ~~print(f.read())~~

--- orig.py	2026-10-17 17:46:44.671807560 -0400
+++ fixed.py	2026-10-17 17:46:45.054889622 -0400
@@ -1,6 +1,4 @@
 with open('tmp.txt', 'w') as f:
     f.write(b'abc')
-if 0:
-    pass
 with open('tmp.txt', 'r') as f:
     print(f.read())

r1-p003 · only-statement-in-blank-line-formatting-tools

1~~if 1:~~

2 ~~pass~~

3~~print(__name__)~~

--- orig.py	2026-10-17 17:46:45.272936265 -0400
+++ fixed.py	2026-10-17 17:46:45.428969643 -0400
@@ -1,3 +1 @@
-if 1:
-    pass
 print(__name__)

__main__

r1-p004 · ellipsis-as-intentional-stub-api-skeleton

1~~def f():~~

2 ~~if True:~~

3 ~~...~~

4 ~~return 1~~

5~~print(f())~~

--- orig.py	2026-10-17 17:46:45.534992323 -0400
+++ fixed.py	2026-10-17 17:46:45.692025914 -0400
@@ -1,5 +1,3 @@
 def f():
-    if True:
-        ...
     return 1
 print(f())

r1-p005 · keyword-only-positional-only-args-kwargs-forwarding-defaults-evaluated-once

1~~def g(a, /, b, *, c=print('default')):~~

2 ~~return a + b + len(str(c))~~

3~~if 0:~~

4 ~~pass~~

5~~print(g(1, 2, c=3))~~

--- orig.py	2026-10-17 17:46:45.797048380 -0400
+++ fixed.py	2026-10-17 17:46:45.957082614 -0400
@@ -1,5 +1,3 @@
 def g(a, /, b, *, c=print('default')):
     return a + b + len(str(c))
-if 0:
-    pass
 print(g(1, 2, c=3))

default
4

r1-p006 · async-def-await-ordering-async-generators

1~~async def gen():~~

2 ~~if False:~~

3 ~~yield 1~~

4 ~~return 2~~

5~~import asyncio~~

6~~print(asyncio.run(gen()))~~

r1-p007 · mutable-default-arguments-aliasing-after-rewrite

1~~def f(x=[]):~~

2 ~~if 0:~~

3 ~~pass~~

4 ~~x.append(1)~~

5 ~~return x~~

6~~print(f())~~

7~~print(f())~~

--- orig.py	2026-10-17 17:46:46.408178966 -0400
+++ fixed.py	2026-10-17 17:46:46.573214211 -0400
@@ -1,6 +1,4 @@
 def f(x=[]):
-    if 0:
-        pass
     x.append(1)
     return x
 print(f())

[1]
[1, 1]

r1-p008 · truthiness-custom-bool-len-none-falsy-is-vs-equals

1~~class C:~~

2 ~~def __bool__(self):~~

3 ~~return True~~

4~~c = C()~~

5~~if c:~~

6 ~~pass~~

7~~print(bool(c))~~

--- orig.py	2026-10-17 17:46:46.670234931 -0400
+++ fixed.py	2026-10-17 17:46:46.835270176 -0400
@@ -2,6 +2,4 @@
     def __bool__(self):
         return True
 c = C()
-if c:
-    pass
 print(bool(c))

True

r2-p001 · Evaluation Order Side Effects - Merged/Duplicated Condition

1~~counter = [0]~~

2~~def inc():~~

3 ~~counter[0] += 1~~

4 ~~return counter[0]~~

5~~val = []~~

6~~if inc() > 0:~~

7 ~~val.append(inc()) # Should append 2~~

8~~print('inc calls:', counter[0], 'value:', val)~~

inc calls: 2 value: [2]

r2-p002 · Source Generation Scaffolding Dependency

1~~# GENERATED_CODE_START~~

2~~if TEMPLATE_FLAG:~~

3 ~~pass # Stub for injected logic~~

4~~# GENERATED_CODE_END~~

5~~TEMPLATE_FLAG = False~~

6~~print('Template flag present:', 'GENERATED_CODE_START' in open(__file__).read())~~

r2-p003 · Name Condition Overridden __bool__ Side Effect

1~~class BoolCounter:~~

2 ~~def __init__(self):~~

3 ~~self.count = 0~~

4 ~~def __bool__(self):~~

5 ~~self.count += 1~~

6 ~~return self.count < 2 # True once, then False~~

7~~x = BoolCounter()~~

8~~result = []~~

9~~if x:~~

10 ~~result.append('first')~~

11~~if x: # Second eval should be False -> no append~~

12 ~~result.append('second')~~

13~~print('bool calls:', x.count, 'results:', result)~~

bool calls: 2 results: ['first']

r2-p004 · Comment Stripping Alters Documentation

1~~debug_mode = False # Set via deploy script~~

2~~if debug_mode:~~

3 ~~pass # Enable verbose logging in dev~~

4~~print('Debug comment preserved:', 'verbose logging' in open(__file__).read())~~

Debug comment preserved: True

r2-p005 · Iterator Consumption in Condition (generated program does not parse: Traceback (most recent call last):)

1~~def gen():~~

2 ~~yield 1~~

3 ~~yield 2~~

4 ~~g = gen()~~

5~~if any(g): # Consumes first item (1), leaves generator exhausted~~

6 ~~print('Second any:', list(g)) # Should be [], but fix may re-evaluate condition~~

7~~print('Generator after:', list(gen())) # Fresh gen for comparison~~

r2-p006 · Chained Comparison Hinders Debugging

1~~a, b, c = 1, 2, 3~~

2~~if a < b < c:~~

3 ~~pass # Set breakpoint here to inspect a,b,c~~

4~~print('Chain holds:', a < b and b < c) # Same logic, but now expr stmt - no breakpoint hook~~

Chain holds: True

r2-p007 · Numeric Coercion Edge Case with Division

1~~x = 5~~

2~~y = 2~~

3~~if x / y > 2: # 2.5 > 2 -> True~~

4 ~~pass~~

5~~print('Division result:', x / y)~~

6~~print('Comparison outcome:', x / y > 2)~~

7~~# If rule duplicates condition, division re-evaluated (same result, but hazard is expression reuse)~~

Division result: 2.5
Comparison outcome: True

r2-p008 · F-string Repr/Src in Condition with Nested Quotes

1~~name = "Alice"~~

2~~if f"User '{name}'" == "User 'Alice'": # Contains single quotes inside double~~

3 ~~pass~~

4~~print('F-string evaluated:', f"User '{name}'")~~

5~~print('Match:', f"User '{name}'" == "User 'Alice'")~~

F-string evaluated: User 'Alice'
Match: True