fix: preserve parentheses for same-precedence different operators

parser.go

@@ -1933,11 +1933,11 @@ func (be *BinaryOpExpr) appendStringNoKeepMetricNames(dst []byte) []byte {
 }
 
 func (be *BinaryOpExpr) needLeftParens() bool {
-	return needBinaryOpArgParens(be.Left, be.Op)
+	return needBinaryOpArgParens(be.Left, be.Op, false)
 }
 
 func (be *BinaryOpExpr) needRightParens() bool {
-	if needBinaryOpArgParens(be.Right, be.Op) {
+	if needBinaryOpArgParens(be.Right, be.Op, true) {
 		return true
 	}
 	switch t := be.Right.(type) {
@@ -1974,7 +1974,7 @@ func (be *BinaryOpExpr) appendModifiers(dst []byte) []byte {
 	return dst
 }
 
-func needBinaryOpArgParens(arg Expr, parentOp string) bool {
+func needBinaryOpArgParens(arg Expr, parentOp string, isRight bool) bool {
 	switch t := arg.(type) {
 	case *BinaryOpExpr:
 		// Parens are required when the child op priority not equal to parent o one.
@@ -1984,6 +1984,15 @@ func needBinaryOpArgParens(arg Expr, parentOp string) bool {
 		}
 
 		// Same op: parens are only needed when the sub-expression is not a simple leaf chain.
+		if t.Op != parentOp {
+			if isRight && !isRightAssociativeBinaryOp(parentOp) {
+				return true
+			}
+			if !isRight && isRightAssociativeBinaryOp(parentOp) {
+				return true
+			}
+		}
+
 		return !isBinaryOpLeafSimple(t)
 	case *RollupExpr:
 		if be, ok := t.Expr.(*BinaryOpExpr); ok && be.KeepMetricNames {

parser_test.go

@@ -399,6 +399,26 @@ func TestParseSuccess(t *testing.T) {
 	// parensExpr
 	another(`(-foo + ((bar) / (baz))) + ((23))`, `0 - foo + (bar / baz) + 23`)
 	another(`(FOO + ((Bar) / (baZ))) + ((23))`, `FOO + (Bar / baZ) + 23`)
+
+	same(`a + (b - c)`)
+	same(`a - (b + c)`)
+	same(`a * (b / c)`)
+	same(`a * (b % c)`)
+	same(`a / (b * c)`)
+	same(`a / (b % c)`)
+	same(`a % (b * c)`)
+	another(`(a - b) + c`, `a - b + c`)
+	another(`(a / b) * c`, `a / b * c`)
+	another(`a + (b + c)`, `a + b + c`)
+	another(`a * (b * c)`, `a * b * c`)
+	another(`(a + b) - c`, `a + b - c`)
+	another(`(a * b) / c`, `a * b / c`)
+	same(`a and (b unless c)`)
+	same(`a unless (b and c)`)
+	another(`(a ^ b) ^ c`, `a ^ b ^ c`)
+	another(`a ^ (b ^ c)`, `a ^ b ^ c`)
+	same(`a / (b * c)`)
+
 	same(`(foo, bar)`)
 	another(`((foo, bar),(baz))`, `((foo, bar), baz)`)
 	same(`(foo, (bar, baz), ((x, y), (z, y), xx))`)

utils_example_test.go

@@ -24,5 +24,5 @@ func ExampleExpandWithExprs() {
 	fmt.Printf("%s\n", pql)
 
 	// Output:
-	// 100 * disk_free_bytes{job="$job",instance="$instance"} / disk_total_bytes{job="$job",instance="$instance"}
+	// 100 * (disk_free_bytes{job="$job",instance="$instance"} / disk_total_bytes{job="$job",instance="$instance"})
 }