/**

* @name Iterator does not return self from __iter__ method

* @description Iterator does not return self from __iter__ method, violating the iterator protocol.

* @kind problem

* @tags reliability

* correctness

* @problem.severity error

* @sub-severity low

* @precision high

* @id py/iter-returns-non-self

*/

import python

Function iter_method(ClassValue t) { result = t.lookup("__iter__").(FunctionValue).getScope() }

predicate is_self(Name value, Function f) { value.getVariable() = f.getArg(0).(Name).getVariable() }

predicate returns_non_self(Function f) {

exists(f.getFallthroughNode())

or

exists(Return r | r.getScope() = f and not is_self(r.getValue(), f))

or

exists(Return r | r.getScope() = f and not exists(r.getValue()))

}

from ClassValue t, Function iter

where t.isIterator() and iter = iter_method(t) and returns_non_self(iter)

select t, "Class " + t.getName() + " is an iterator but its $@ method does not return 'self'.",

iter, iter.getName()