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63 lines (59 loc) · 2.14 KB
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/**
* @name Unnecessary lambda
* @description A lambda is used that calls through to a function without modifying any parameters
* @kind problem
* @tags quality
* maintainability
* useless-code
* @problem.severity recommendation
* @sub-severity high
* @precision high
* @id py/unnecessary-lambda
*/
import python
private import LegacyPointsTo
/* f consists of a single return statement, whose value is a call. The arguments of the call are exactly the parameters of f */
predicate simple_wrapper(Lambda l, Expr wrapped) {
exists(Function f, Call c | f = l.getInnerScope() and c = l.getExpression() |
wrapped = c.getFunc() and
count(f.getAnArg()) = count(c.getAnArg()) and
forall(int arg | exists(f.getArg(arg)) | f.getArgName(arg) = c.getArg(arg).(Name).getId()) and
/* Either no **kwargs or they must match */
(
not exists(f.getKwarg()) and not exists(c.getKwargs())
or
f.getKwarg().(Name).getId() = c.getKwargs().(Name).getId()
) and
/* Either no *args or they must match */
(
not exists(f.getVararg()) and not exists(c.getStarargs())
or
f.getVararg().(Name).getId() = c.getStarargs().(Name).getId()
) and
/* No named parameters in call */
not exists(c.getAKeyword())
) and
// f is not necessarily a drop-in replacement for the lambda if there are default argument values
not exists(l.getArgs().getADefault())
}
/* The expression called will refer to the same object if evaluated when the lambda is created or when the lambda is executed. */
predicate unnecessary_lambda(Lambda l, ExprWithPointsTo e) {
simple_wrapper(l, e) and
(
/* plain class */
exists(ClassValue c | e.pointsTo(c))
or
/* plain function */
exists(FunctionValue f | e.pointsTo(f))
or
/* bound-method of enclosing instance */
exists(ClassValue cls, Attribute a | cls.getScope() = l.getScope().getScope() and a = e |
a.getObject().(Name).getId() = "self" and
cls.hasAttribute(a.getName())
)
)
}
from Lambda l, Expr e
where unnecessary_lambda(l, e)
select l,
"This 'lambda' is just a simple wrapper around a callable object. Use that object directly."