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69 lines
1.8 KiB
Plaintext
69 lines
1.8 KiB
Plaintext
/**
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* @name Comparison using is when operands support `__eq__`
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* @description Comparison using 'is' when equivalence is not the same as identity
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* @kind problem
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* @tags reliability
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* correctness
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* @problem.severity warning
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* @sub-severity low
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* @precision high
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* @id py/comparison-using-is
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*/
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import python
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/** Holds if the comparison `comp` uses `is` or `is not` (represented as `op`) to compare its `left` and `right` arguments. */
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predicate comparison_using_is(Compare comp, ControlFlowNode left, Cmpop op, ControlFlowNode right) {
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exists(CompareNode fcomp | fcomp = comp.getAFlowNode() |
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fcomp.operands(left, op, right) and
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(op instanceof Is or op instanceof IsNot)
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)
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}
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private predicate cpython_interned_value(Expr e) {
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exists(string text | text = e.(StringLiteral).getText() |
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text.length() = 0
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or
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text.length() = 1 and text.regexpMatch("[U+0000-U+00ff]")
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)
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or
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exists(int i | i = e.(IntegerLiteral).getN().toInt() | -5 <= i and i <= 256)
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or
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exists(Tuple t | t = e and not exists(t.getAnElt()))
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}
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predicate uninterned_literal(Expr e) {
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(
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e instanceof StringLiteral
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or
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e instanceof IntegerLiteral
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or
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e instanceof FloatLiteral
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or
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e instanceof Dict
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or
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e instanceof List
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or
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e instanceof Tuple
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) and
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not cpython_interned_value(e)
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}
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from Compare comp, Cmpop op, string alt
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where
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exists(ControlFlowNode left, ControlFlowNode right |
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comparison_using_is(comp, left, op, right) and
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(
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op instanceof Is and alt = "=="
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or
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op instanceof IsNot and alt = "!="
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)
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uninterned_literal(left.getNode())
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or
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uninterned_literal(right.getNode())
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)
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select comp,
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"Values compared using '" + op.getSymbol() +
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"' when equivalence is not the same as identity. Use '" + alt + "' instead."
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