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JS: fix cfg and dataflow for logical compound assignments #6459

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Merged
codeql-ci merged 1 commit into from
Aug 11, 2021
Merged

JS: fix cfg and dataflow for logical compound assignments #6459

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4 changes: 2 additions & 2 deletions javascript/extractor/src/com/semmle/js/extractor/CFGExtractor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1659,7 +1659,7 @@ public Void visit(MemberDefinition<?> nd, SuccessorInfo i) {

@Override
public Void visit(AssignmentExpression nd, SuccessorInfo i) {
// `a &&= b` expands to `a || (a = b);`
// `a &&= b` expands to `a && (a = b);`
// The CFG is a conditional assignment, so we go through the assignment `nd` last.
if ("&&=".equals(nd.getOperator()) || "||=".equals(nd.getOperator()) || "??=".equals(nd.getOperator())) {
if ("&&=".equals(nd.getOperator())) {
Expand All @@ -1673,7 +1673,7 @@ public Void visit(AssignmentExpression nd, SuccessorInfo i) {
visitWithSuccessors(nd.getLeft(), union(First.of(nd.getRight()), i.getAllSuccessors()));
}

visitWithSuccessors(nd.getRight(), First.of(nd)); // from right to assignment.
visitWithSuccessors(nd.getRight(), nd); // from right to assignment.

writeSuccessors(nd, i.getGuardedSuccessors(nd));
} else {
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8 changes: 4 additions & 4 deletions javascript/extractor/tests/es2021/output/trap/assign.js.trap
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Expand Up @@ -556,7 +556,7 @@ hasLocation(#20168,#20109)
successor(#20161,#20164)
successor(#20164,#20165)
successor(#20164,#20168)
successor(#20165,#20164)
successor(#20165,#20162)
successor(#20162,#20168)
successor(#20156,#20159)
#20169=*
Expand All @@ -569,7 +569,7 @@ hasLocation(#20170,#20093)
successor(#20170,#20160)
successor(#20159,#20169)
successor(#20159,#20170)
successor(#20160,#20159)
successor(#20160,#20157)
successor(#20157,#20161)
successor(#20151,#20154)
#20171=*
Expand All @@ -582,7 +582,7 @@ hasLocation(#20172,#20085)
successor(#20172,#20156)
successor(#20154,#20171)
successor(#20154,#20172)
successor(#20155,#20154)
successor(#20155,#20152)
successor(#20152,#20156)
successor(#20141,#20147)
successor(#20150,#20143)
Expand All @@ -601,7 +601,7 @@ hasLocation(#20174,#20063)
successor(#20174,#20134)
successor(#20139,#20173)
successor(#20139,#20174)
successor(#20140,#20139)
successor(#20140,#20137)
successor(#20137,#20134)
successor(#20136,#20139)
successor(#20134,#20141)
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10 changes: 10 additions & 0 deletions javascript/ql/src/semmle/javascript/dataflow/DataFlow.qll
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Expand Up @@ -1495,6 +1495,16 @@ module DataFlow {
predExpr = succExpr.(NonNullAssertion).getExpression()
or
predExpr = succExpr.(ExpressionWithTypeArguments).getExpression()
or
(
succExpr instanceof AssignLogOrExpr or
succExpr instanceof AssignLogAndExpr or
succExpr instanceof AssignNullishCoalescingExpr
) and
(
predExpr = succExpr.(CompoundAssignExpr).getLhs() or
predExpr = succExpr.(CompoundAssignExpr).getRhs()
)
)
or
// flow from 'this' parameter into 'this' expressions
Expand Down
17 changes: 17 additions & 0 deletions javascript/ql/test/query-tests/Statements/UselessConditional/oreq.js
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@@ -0,0 +1,17 @@
function f() {
let foo;
if (bar) foo ||= [];
if (foo);
};

function g() {
let foo;
if (bar) foo ??= [];
if (foo);
};

function h() {
let foo = true;
if (bar) foo &&= false;
if (foo);
}