Fix print with precedence (expr-lang#678)

* feat: extract code for compiling equal operator

* fix: fix unary and binary node print

consider the precedence of operators and their associative law when printing unary and binary nodes

---------

Co-authored-by: Anton Medvedev <[email protected]>

Author: 2 people

ast/print.go

@@ -50,8 +50,13 @@ func (n *UnaryNode) String() string {
 		op = fmt.Sprintf("%s ", n.Operator)
 	}
 	wrap := false
-	switch n.Node.(type) {
-	case *BinaryNode, *ConditionalNode:
+	switch b := n.Node.(type) {
+	case *BinaryNode:
+		if operator.Binary[b.Operator].Precedence <
+			operator.Unary[n.Operator].Precedence {
+			wrap = true
+		}
+	case *ConditionalNode:
 		wrap = true
 	}
 	if wrap {
@@ -68,10 +73,21 @@ func (n *BinaryNode) String() string {
 	var lhs, rhs string
 	var lwrap, rwrap bool
 
+	if l, ok := n.Left.(*UnaryNode); ok {
+		if operator.Unary[l.Operator].Precedence <
+			operator.Binary[n.Operator].Precedence {
+			lwrap = true
+		}
+	}
 	if lb, ok := n.Left.(*BinaryNode); ok {
 		if operator.Less(lb.Operator, n.Operator) {
 			lwrap = true
 		}
+		if operator.Binary[lb.Operator].Precedence == 
+			operator.Binary[n.Operator].Precedence && 
+			operator.Binary[n.Operator].Associativity == operator.Right {
+			lwrap = true
+		}
 		if lb.Operator == "??" {
 			lwrap = true
 		}
@@ -83,6 +99,11 @@ func (n *BinaryNode) String() string {
 		if operator.Less(rb.Operator, n.Operator) {
 			rwrap = true
 		}
+		if operator.Binary[rb.Operator].Precedence == 
+			operator.Binary[n.Operator].Precedence && 
+			operator.Binary[n.Operator].Associativity == operator.Left {
+			rwrap = true
+		}
 		if operator.IsBoolean(rb.Operator) && n.Operator != rb.Operator {
 			rwrap = true
 		}

ast/print_test.go

@@ -78,6 +78,11 @@ func TestPrint(t *testing.T) {
 		{`{("a" + "b"): 42}`, `{("a" + "b"): 42}`},
 		{`(One == 1 ? true : false) && Two == 2`, `(One == 1 ? true : false) && Two == 2`},
 		{`not (a == 1 ? b > 1 : b < 2)`, `not (a == 1 ? b > 1 : b < 2)`},
+		{`(-(1+1)) ** 2`, `(-(1 + 1)) ** 2`},
+		{`2 ** (-(1+1))`, `2 ** -(1 + 1)`},
+		{`(2 ** 2) ** 3`, `(2 ** 2) ** 3`},
+		{`(3 + 5) / (5 % 3)`, `(3 + 5) / (5 % 3)`},
+		{`(-(1+1)) == 2`, `-(1 + 1) == 2`},
 	}
 
 	for _, tt := range tests {