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Python: Port NonIteratorInForLoop.ql #21688

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Python: Port NonIteratorInForLoop.ql
tausbn Feb 20, 2026
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Python: Exclude iterators guarded by `isinstance` checks
tausbn Mar 16, 2026
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Python: Port NonIteratorInForLoop.ql 
Uses the `DuckTyping` module to approximate whether something is likely
to be an iterator or not.

We lose one test result due to the fact that we don't know what to do
about `for ... in 1` (because `1` is an instance of a built-in). I'm
going to defer addressing this until we get some modelling of built-in
types.
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@tausbn
tausbn committed Apr 9, 2026
commit 32c4db4e50f4ff3b51057dd53bb053279b6eef45
21 changes: 10 additions & 11 deletions python/ql/src/Statements/NonIteratorInForLoop.ql
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Expand Up @@ -12,16 +12,15 @@
*/

import python
private import LegacyPointsTo
private import semmle.python.dataflow.new.internal.DataFlowDispatch

from For loop, ControlFlowNodeWithPointsTo iter, Value v, ClassValue t, ControlFlowNode origin
from For loop, Expr iter, Class cls
where
loop.getIter().getAFlowNode() = iter and
iter.pointsTo(_, v, origin) and
v.getClass() = t and
not t.isIterable() and
not t.failedInference(_) and
not v = Value::named("None") and
not t.isDescriptorType()
select loop, "This for-loop may attempt to iterate over a $@ of class $@.", origin,
"non-iterable instance", t, t.getName()
iter = loop.getIter() and
classInstanceTracker(cls).asExpr() = iter and
not DuckTyping::isIterable(cls) and
not DuckTyping::isDescriptor(cls) and
not (loop.isAsync() and DuckTyping::hasMethod(cls, "__aiter__")) and
not DuckTyping::hasUnresolvedBase(getADirectSuperclass*(cls))
select loop, "This for-loop may attempt to iterate over a $@ of class $@.", iter,
"non-iterable instance", cls, cls.getName()
3 changes: 1 addition & 2 deletions python/ql/test/3/query-tests/Statements/iter/NonIteratorInForLoop.expected
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| async_iterator.py:26:11:26:34 | For | This for-loop may attempt to iterate over a $@ of class $@. | async_iterator.py:26:20:26:33 | ControlFlowNode for MissingAiter() | non-iterable instance | async_iterator.py:13:1:13:19 | class MissingAiter | MissingAiter |
| statements_test.py:34:5:34:19 | For | This for-loop may attempt to iterate over a $@ of class $@. | statements_test.py:34:18:34:18 | ControlFlowNode for IntegerLiteral | non-iterable instance | file://:0:0:0:0 | builtin-class int | int |
| async_iterator.py:26:11:26:34 | For | This for-loop may attempt to iterate over a $@ of class $@. | async_iterator.py:26:20:26:33 | MissingAiter() | non-iterable instance | async_iterator.py:13:1:13:19 | Class MissingAiter | MissingAiter |
2 changes: 1 addition & 1 deletion python/ql/test/query-tests/Statements/general/NonIteratorInForLoop.expected
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@@ -1 +1 @@
| test.py:50:1:50:23 | For | This for-loop may attempt to iterate over a $@ of class $@. | test.py:50:10:50:22 | ControlFlowNode for NonIterator() | non-iterable instance | test.py:45:1:45:26 | class NonIterator | NonIterator |
| test.py:50:1:50:23 | For | This for-loop may attempt to iterate over a $@ of class $@. | test.py:50:10:50:22 | NonIterator() | non-iterable instance | test.py:45:1:45:26 | Class NonIterator | NonIterator |