Merge pull request #19554 from joefarebrother/python-qual-iter-not-return-self

Python: Modernize iter not returning self query

python/ql/test/query-tests/Functions/general/IterReturnsNonSelf.expected

@@ -1 +0,0 @@
-| protocols.py:54:1:54:29 | class AlmostIterator | Class AlmostIterator is an iterator but its $@ method does not return 'self'. | protocols.py:62:5:62:23 | Function __iter__ | __iter__ |

python/ql/test/query-tests/Functions/iterators/IterReturnsNonSelf.expected

@@ -0,0 +1,2 @@
+| test.py:5:5:5:23 | Function __iter__ | Iter method of iterator $@ does not return `self`. | test.py:1:1:1:11 | Class Bad1 | Bad1 |
+| test.py:51:5:51:23 | Function __iter__ | Iter method of iterator $@ does not return `self`. | test.py:42:1:42:21 | Class FalsePositive1 | FalsePositive1 |

python/ql/test/query-tests/Functions/iterators/test.py

@@ -0,0 +1,53 @@
+class Bad1:
+    def __next__(self):
+        return 0 
+
+    def __iter__(self): # BAD: Iter does not return self
+        yield 0 
+
+class Good1:
+    def __next__(self):
+        return 0 
+
+    def __iter__(self): # GOOD: iter returns self
+        return self 
+
+class Good2:
+    def __init__(self):
+        self._it = iter([0,0,0])
+
+    def __next__(self):
+        return next(self._it)
+
+    def __iter__(self): # GOOD: iter and next are wrappers around a field
+        return self._it.__iter__()
+    
+class Good3:
+    def __init__(self):
+        self._it = iter([0,0,0])
+
+    def __next__(self):
+        return self._it.__next__()
+
+    def __iter__(self): # GOOD: iter and next are wrappers around a field
+        return self._it
+
+class Good4:
+    def __next__(self):
+        return 0
+
+    def __iter__(self): # GOOD: this is an equivalent iterator to `self`.
+        return iter(self.__next__, None)
+
+class FalsePositive1:
+    def __init__(self):
+        self._it = None 
+
+    def __next__(self):
+        if self._it is None:
+            self._it = iter(self)
+        return next(self._it)
+
+    def __iter__(self): # SPURIOUS, GOOD: implementation of next ensures the iterator is equivalent to the one returned by iter, but this is not detected.
+        yield 0 
+        yield 0