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codeql/python/ql/src/Statements/ShouldUseWithStatement.ql
2018-11-19 15:10:42 +00:00

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/**
* @name Should use a 'with' statement
* @description Using a 'try-finally' block to ensure only that a resource is closed makes code more
* difficult to read.
* @kind problem
* @tags maintainability
* readability
* convention
* @problem.severity recommendation
* @sub-severity high
* @precision very-high
* @id py/should-use-with
*/
import python
predicate calls_close(Call c) {
exists (Attribute a | c.getFunc() = a and a.getName() = "close")
}
predicate
only_stmt_in_finally(Try t, Call c) {
exists(ExprStmt s | t.getAFinalstmt() = s and s.getValue() = c and strictcount(t.getAFinalstmt()) = 1)
}
predicate points_to_context_manager(ControlFlowNode f, ClassObject cls) {
cls.isContextManager() and
forex(Object obj | f.refersTo(obj) | f.refersTo(obj, cls, _))
}
from Call close, Try t, ClassObject cls
where only_stmt_in_finally(t, close) and calls_close(close) and
exists(ControlFlowNode f | f = close.getFunc().getAFlowNode().(AttrNode).getObject() |
points_to_context_manager(f, cls))
select close, "Instance of context-manager class $@ is closed in a finally block. Consider using 'with' statement.", cls, cls.getName()