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codeql/python/ql/src/Classes/Comparisons/IncompleteOrdering.ql
2025-07-11 23:08:50 +01:00

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/**
* @name Incomplete ordering
* @description Class defines ordering comparison methods, but does not define both strict and nonstrict ordering methods, to ensure all four comparison operators behave as expected.
* @kind problem
* @tags quality
* reliability
* correctness
* @problem.severity warning
* @sub-severity low
* @precision very-high
* @id py/incomplete-ordering
*/
import python
import semmle.python.dataflow.new.internal.DataFlowDispatch
import semmle.python.ApiGraphs
/** Holds if `cls` has the `functools.total_ordering` decorator. */
predicate totalOrdering(Class cls) {
API::moduleImport("functools")
.getMember("total_ordering")
.asSource()
.flowsTo(DataFlow::exprNode(cls.getADecorator()))
}
predicate definesStrictOrdering(Class cls, Function meth) {
meth = cls.getMethod("__lt__")
or
not exists(cls.getMethod("__lt__")) and
meth = cls.getMethod("__gt__")
}
predicate definesNonStrictOrdering(Class cls, Function meth) {
meth = cls.getMethod("__le__")
or
not exists(cls.getMethod("__le__")) and
meth = cls.getMethod("__ge__")
}
predicate missingComparison(Class cls, Function defined, string missing) {
definesStrictOrdering(cls, defined) and
not definesNonStrictOrdering(getADirectSuperclass*(cls), _) and
missing = "__le__ or __ge__"
or
definesNonStrictOrdering(cls, defined) and
not definesStrictOrdering(getADirectSuperclass*(cls), _) and
missing = "__lt__ or __gt__"
}
from Class cls, Function defined, string missing
where
not totalOrdering(cls) and
missingComparison(cls, defined, missing)
select cls, "This class implements $@, but does not implement " + missing + ".", defined,
defined.getName()