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Fix StackOverflowError in Kotlin parser for deeply nested binary expressions #7083

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Fix StackOverflowError in Kotlin parser for deeply nested binary expressions #7083

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36 changes: 30 additions & 6 deletions rewrite-kotlin/src/main/java/org/openrewrite/kotlin/internal/KotlinTreeParserVisitor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1866,15 +1866,39 @@ public J visitArgument(KtValueArgument argument, ExecutionContext data) {

@Override
public J visitBinaryExpression(KtBinaryExpression expression, ExecutionContext data) {
assert expression.getLeft() != null;
assert expression.getRight() != null;
// Collect left-spine of nested binary expressions to process iteratively,
// avoiding StackOverflowError on deeply nested expressions (e.g. 2000+ concatenations)
List<KtBinaryExpression> spine = new ArrayList<>();
KtExpression leftmost = expression;
while (leftmost instanceof KtBinaryExpression) {
spine.add((KtBinaryExpression) leftmost);
leftmost = ((KtBinaryExpression) leftmost).getLeft();
}

// Visit the deepest left operand (not a binary expression)
assert leftmost != null;
J leftJ = leftmost.accept(this, data);

// Process each binary expression from innermost to outermost
J result = null;
for (int i = spine.size() - 1; i >= 0; i--) {
KtBinaryExpression binExpr = spine.get(i);
assert binExpr.getRight() != null;

Expression left = convertToExpression(leftJ).withPrefix(Space.EMPTY);
result = visitSingleBinaryExpression(binExpr, left, data);
leftJ = result;
}

return result;
}

private J visitSingleBinaryExpression(KtBinaryExpression expression, Expression left, ExecutionContext data) {
KtOperationReferenceExpression operationReference = expression.getOperationReference();
J.Binary.Type javaBinaryType = mapJBinaryType(operationReference);
J.AssignmentOperation.Type assignmentOperationType = javaBinaryType == null ? mapAssignmentOperationType(operationReference) : null;
K.Binary.Type kotlinBinaryType = javaBinaryType == null && assignmentOperationType == null ? mapKBinaryType(operationReference) : null;

Expression left = convertToExpression(expression.getLeft().accept(this, data)).withPrefix(Space.EMPTY);
Expression right = convertToExpression((expression.getRight()).accept(this, data))
.withPrefix(prefix(expression.getRight()));
JavaType type = type(expression);
Expand Down Expand Up @@ -1921,7 +1945,7 @@ public J visitBinaryExpression(KtBinaryExpression expression, ExecutionContext d
));
}

return mapFunctionCall(expression, data);
return mapFunctionCall(expression, left, data);
}

private J.AssignmentOperation.@Nullable Type mapAssignmentOperationType(KtOperationReferenceExpression operationReference) {
Expand Down Expand Up @@ -3398,12 +3422,12 @@ else if (elementType == KtTokens.OROR)
}
}

private J.MethodInvocation mapFunctionCall(KtBinaryExpression expression, ExecutionContext data) {
private J.MethodInvocation mapFunctionCall(KtBinaryExpression expression, Expression precomputedLeft, ExecutionContext data) {
Markers markers = Markers.EMPTY
.addIfAbsent(new Infix(randomId()))
.addIfAbsent(new Extension(randomId()));

Expression selectExp = convertToExpression(requireNonNull(expression.getLeft()).accept(this, data).withPrefix(prefix(expression.getLeft())));
Expression selectExp = precomputedLeft.withPrefix(prefix(expression.getLeft()));
JRightPadded<Expression> select = padRight(selectExp, Space.EMPTY);
J.Identifier name = (J.Identifier) expression.getOperationReference().accept(this, data); // createIdentifier(operation, Space.EMPTY, methodInvocationType(expression));

Expand Down