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869e33e38c
Excluded for now: unnecassary-delete; since the pattern is often intentional to break reference cycles, which the query doesn't account for; so uncertain about its claim of high precision
77 lines
2.5 KiB
Plaintext
77 lines
2.5 KiB
Plaintext
/**
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* @name Unused global variable
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* @description Global variable is defined but not used
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* @kind problem
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* @tags quality
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* maintainability
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* useless-code
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* external/cwe/cwe-563
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* @problem.severity recommendation
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* @sub-severity low
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* @precision high
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* @id py/unused-global-variable
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*/
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import python
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import Definition
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/**
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* Whether the module contains an __all__ definition,
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* but it is more complex than a simple list of strings
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*/
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predicate complex_all(Module m) {
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exists(Assign a, GlobalVariable all |
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a.defines(all) and a.getScope() = m and all.getId() = "__all__"
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not a.getValue() instanceof List
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or
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exists(Expr e | e = a.getValue().(List).getAnElt() | not e instanceof StringLiteral)
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)
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or
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exists(Call c, GlobalVariable all |
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c.getFunc().(Attribute).getObject() = all.getALoad() and
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c.getScope() = m and
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all.getId() = "__all__"
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)
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}
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predicate used_in_forward_declaration(Name used, Module mod) {
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exists(StringLiteral s, Annotation annotation |
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s.getS() = used.getId() and
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s.getEnclosingModule() = mod and
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annotation.getASubExpression*() = s
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)
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}
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predicate unused_global(Name unused, GlobalVariable v) {
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not exists(ImportingStmt is | is.contains(unused)) and
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forex(DefinitionNode defn | defn.getNode() = unused |
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not defn.getValue().getNode() instanceof FunctionExpr and
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not defn.getValue().getNode() instanceof ClassExpr and
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not exists(Name u |
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// A use of the variable
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u.uses(v)
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// That is reachable from this definition, directly
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defn.strictlyReaches(u.getAFlowNode())
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or
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// indirectly
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defn.getBasicBlock().reachesExit() and u.getScope() != unused.getScope()
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) and
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not unused.getEnclosingModule().getAnExport() = v.getId() and
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not exists(unused.getParentNode().(ClassDef).getDefinedClass().getADecorator()) and
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not exists(unused.getParentNode().(FunctionDef).getDefinedFunction().getADecorator()) and
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unused.defines(v) and
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not name_acceptable_for_unused_variable(v) and
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not complex_all(unused.getEnclosingModule())
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) and
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not used_in_forward_declaration(unused, unused.getEnclosingModule())
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}
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from Name unused, GlobalVariable v
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where
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unused_global(unused, v) and
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// If unused is part of a tuple, count it as unused if all elements of that tuple are unused.
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forall(Name el | el = unused.getParentNode().(Tuple).getAnElt() | unused_global(el, _))
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select unused, "The global variable '" + v.getId() + "' is not used."
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