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codeql/javascript/ql/src/Expressions/MissingAwait.ql
2020-04-02 11:35:09 +01:00

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/**
* @name Missing await
* @description Using a promise without awaiting its result can lead to unexpected behavior.
* @kind problem
* @problem.severity warning
* @id js/missing-await
* @tags correctness
* @precision high
*/
import javascript
/**
* Holds if `call` is a call to an `async` function.
*/
predicate isAsyncCall(DataFlow::CallNode call) {
// If a callee is known, and all known callees are async, assume all
// possible callees are async.
forex(Function callee | call.getACallee() = callee | callee.isAsync())
}
/**
* Holds if `node` is always a promise.
*/
predicate isPromise(DataFlow::SourceNode node, boolean nullable) {
isAsyncCall(node) and
nullable = false
or
not isAsyncCall(node) and
node.asExpr().getType() instanceof PromiseType and
nullable = true
}
/**
* Holds the result of `e` is used in a way that doesn't make sense for Promise objects.
*/
predicate isBadPromiseContext(Expr expr) {
exists(BinaryExpr binary |
expr = binary.getAnOperand() and
not binary instanceof LogicalExpr and
not binary instanceof InstanceofExpr
)
or
expr = any(LogicalBinaryExpr e).getLeftOperand()
or
exists(UnaryExpr e |
expr = e.getOperand() and
not e instanceof VoidExpr and
not e instanceof DeleteExpr
)
or
expr = any(UpdateExpr e).getOperand()
or
expr = any(ConditionalExpr e).getCondition()
or
expr = any(IfStmt stmt).getCondition()
or
expr = any(ForInStmt stmt).getIterationDomain()
or
expr = any(IndexExpr e).getIndex()
}
string tryGetPromiseExplanation(Expr e) {
result = "The value '" + e.(VarAccess).getName() + "' is always a promise."
or
result = "The call to '" + e.(CallExpr).getCalleeName() + "' always returns a promise."
}
string getPromiseExplanation(Expr e) {
result = tryGetPromiseExplanation(e)
or
not exists(tryGetPromiseExplanation(e)) and
result = "This value is always a promise."
}
from Expr expr, boolean nullable
where
isBadPromiseContext(expr) and
isPromise(expr.flow().getImmediatePredecessor*(), nullable) and
(
nullable = false
or
expr.inNullSensitiveContext()
)
select expr, "Missing await. " + getPromiseExplanation(expr)