/**
 * @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()