Add else if support

Author: antonmedv

ast/print_test.go

@@ -84,6 +84,7 @@ func TestPrint(t *testing.T) {
 		{`(3 + 5) / (5 % 3)`, `(3 + 5) / (5 % 3)`},
 		{`(-(1+1)) == 2`, `-(1 + 1) == 2`},
 		{`if true { 1 } else { 2 }`, `true ? 1 : 2`},
+		{`if true { 1 } else if false { 2 } else { 3 }`, `true ? 1 : (false ? 2 : 3)`},
 	}
 
 	for _, tt := range tests {

expr_test.go

@@ -1390,6 +1390,10 @@ func TestExpr(t *testing.T) {
 			`if "a" < "b" {let x = "a"; x} else {"abc"}`,
 			"a",
 		},
+		{
+			`if 1 == 2 { "no" } else if 1 == 1 { "yes" } else { "maybe" }`,
+			"yes",
+		},
 		{
 			`1; 2; 3`,
 			3,

parser/parser.go

@@ -334,9 +334,15 @@ func (p *Parser) parseConditionalIf() Node {
 	expr1 := p.parseSequenceExpression()
 	p.expect(Bracket, "}")
 	p.expect(Operator, "else")
-	p.expect(Bracket, "{")
-	expr2 := p.parseSequenceExpression()
-	p.expect(Bracket, "}")
+
+	var expr2 Node
+	if p.current.Is(Operator, "if") {
+		expr2 = p.parseConditionalIf()
+	} else {
+		p.expect(Bracket, "{")
+		expr2 = p.parseSequenceExpression()
+		p.expect(Bracket, "}")
+	}
 
 	return &ConditionalNode{
 		Cond: nodeCondition,

parser/parser_test.go

@@ -659,6 +659,16 @@ world`},
 				Exp1: &BoolNode{Value: true},
 				Exp2: &IdentifierNode{Value: "x"}},
 		},
+		{
+			"if a { 1 } else if b { 2 } else { 3 }",
+			&ConditionalNode{
+				Cond: &IdentifierNode{Value: "a"},
+				Exp1: &IntegerNode{Value: 1},
+				Exp2: &ConditionalNode{
+					Cond: &IdentifierNode{Value: "b"},
+					Exp1: &IntegerNode{Value: 2},
+					Exp2: &IntegerNode{Value: 3}}},
+		},
 		{
 			"1; 2; 3",
 			&SequenceNode{
@@ -1019,6 +1029,12 @@ func TestParse_error(t *testing.T) {
 			`unexpected token Operator("if") (1:5)
  | 1 + if true { 2 } else { 3 }
  | ....^`,
+		},
+		{
+			`if a { 1 } else b`,
+			`unexpected token Identifier("b") (1:17)
+ | if a { 1 } else b
+ | ................^`,
 		},
 		{
 			`list | all(#,,)`,