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Merge pull request #833 from esben-semmle/js/sharpen-cond

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Approved by xiemaisi
This commit is contained in:
semmle-qlci
2019-01-29 08:03:06 +00:00
committed by GitHub
parent 1d28c63703 239fe6e419
commit a5aee9ed0f
4 changed files with 50 additions and 8 deletions
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23
javascript/ql/src/Statements/UselessConditional.ql
View File

@@ -65,17 +65,24 @@ predicate isInitialParameterUse(Expr e) {
}
/**
* Holds if `e` directly uses the returned value from a function call that returns a constant boolean value.
* Holds if `e` directly uses the returned value from functions that return constant boolean values.
*/
predicate isConstantBooleanReturnValue(Expr e) {
// unlike `SourceNode.flowsTo` this will not include uses we have refinement information for
exists(DataFlow::CallNode call | exists(call.analyze().getTheBooleanValue()) |
e = call.asExpr()
or
// also support return values that are assigned to variables
exists(SsaExplicitDefinition ssa |
ssa.getDef().getSource() = call.asExpr() and
ssa.getVariable().getAUse() = e
exists(string b | (b = "true" or b = "false") |
forex(DataFlow::CallNode call, Expr ret |
ret = call.getACallee().getAReturnedExpr() and
(
e = call.asExpr()
or
// also support return values that are assigned to variables
exists(SsaExplicitDefinition ssa |
ssa.getDef().getSource() = call.asExpr() and
ssa.getVariable().getAUse() = e
)
)
|
ret.(BooleanLiteral).getValue() = b
)
)
or

3
javascript/ql/test/query-tests/Statements/UselessConditional/UselessConditional.expected
View File

@@ -22,6 +22,9 @@
| UselessConditional.js:102:19:102:19 | x | This use of variable 'x' always evaluates to false. |
| UselessConditional.js:103:23:103:23 | x | This use of variable 'x' always evaluates to false. |
| UselessConditional.js:109:15:109:16 | {} | This expression always evaluates to true. |
| UselessConditional.js:129:6:129:24 | constantUndefined() | This call to constantUndefined always evaluates to false. |
| UselessConditional.js:135:6:135:32 | constan ... ined1() | This call to constantFalseOrUndefined1 always evaluates to false. |
| UselessConditional.js:139:6:139:32 | constan ... ined2() | This call to constantFalseOrUndefined2 always evaluates to false. |
| UselessConditionalGood.js:58:12:58:13 | x2 | This use of variable 'x2' always evaluates to false. |
| UselessConditionalGood.js:69:12:69:13 | xy | This use of variable 'xy' always evaluates to false. |
| UselessConditionalGood.js:85:12:85:13 | xy | This use of variable 'xy' always evaluates to false. |

31
javascript/ql/test/query-tests/Statements/UselessConditional/UselessConditional.js
View File

@@ -109,4 +109,35 @@ async function awaitFlow(){
if ((x && {}) || y) {} // NOT OK
});
(function(){
function constantFalse1() {
return false;
}
if (constantFalse1()) // OK
return;
function constantFalse2() {
return false;
}
let constantFalse = unknown? constantFalse1 : constantFalse2;
if (constantFalse2()) // OK
return;
function constantUndefined() {
return undefined;
}
if (constantUndefined()) // NOT OK
return;
function constantFalseOrUndefined1() {
return unknown? false: undefined;
}
if (constantFalseOrUndefined1()) // NOT OK
return;
let constantFalseOrUndefined2 = unknown? constantFalse1 : constantUndefined;
if (constantFalseOrUndefined2()) // NOT OK
return;
});
// semmle-extractor-options: --experimental