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UnusedLocalVariable.ql

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/**

* @name Unused local variable

* @description Local variable is defined but not used

* @kind problem

* @tags quality

* maintainability

* useless-code

* external/cwe/cwe-563

* @problem.severity recommendation

* @sub-severity high

* @precision very-high

* @id py/unused-local-variable

*/

import python

import Definition

predicate unused_local(Name unused, LocalVariable v) {

forex(Definition def | def.getNode() = unused |

def.getVariable() = v and

def.isUnused() and

not exists(def.getARedef()) and

not exists(annotation_without_assignment(v)) and

def.isRelevant() and

not v = any(Nonlocal n).getAVariable() and

not exists(def.getNode().getParentNode().(FunctionDef).getDefinedFunction().getADecorator()) and

not exists(def.getNode().getParentNode().(ClassDef).getDefinedClass().getADecorator())

)

}

/**

* Gets any annotation of the local variable `v` that does not also reassign its value.

*

* TODO: This predicate should not be needed. Rather, annotated "assignments" that do not actually

* assign a value should not result in the creation of an SSA variable (which then goes unused).

*/

private AnnAssign annotation_without_assignment(LocalVariable v) {

result.getTarget() = v.getAStore() and

not exists(result.getValue())

}

from Name unused, LocalVariable v

where

unused_local(unused, v) and

// If unused is part of a tuple, count it as unused if all elements of that tuple are unused.

forall(Name el | el = unused.getParentNode().(Tuple).getAnElt() | unused_local(el, _))

select unused, "Variable " + v.getId() + " is not used."