Add ternary expressions

internal/ast/ast.go

@@ -199,3 +199,14 @@ func (l Logical) Pos() Position {
 func (l Logical) Op() string {
 	return l.Value
 }
+
+type Ternary struct {
+	Condition Node
+	IfTrue    Node
+	Else      Node
+	Position  Position
+}
+
+func (t Ternary) Pos() Position {
+	return t.Position
+}

internal/parser/salix.peg

@@ -55,13 +55,15 @@ EndTag = "#!" name:Ident {
     }, nil
 }
 
-ExprTag = "#(" expr:Expr ')' {
+ExprTag = "#(" item:Item ')' {
     return ast.ExprTag{
-        Value:    expr.(ast.Node),
+        Value:    item.(ast.Node),
         Position: getPos(c),
     }, nil
 }
 
+Item = Ternary / Expr
+
 Expr = first:ExprSegment rest:(_ Logical _ ExprSegment)* {
     restSlice := toAnySlice(rest)
     if len(restSlice) == 0 {
@@ -100,7 +102,7 @@ ExprSegment = first:Value rest:(_ Operator _ Value)* {
     return out, nil
 }
 
-ParamList = '(' params:(Expr ( ',' _ Expr )* )? ')' {
+ParamList = '(' params:(Item ( ',' _ Item )* )? ')' {
     paramSlice := toAnySlice(params)
     if len(paramSlice) == 0 {
         return []ast.Node{}, nil
@@ -121,6 +123,14 @@ Value = not:"!"? node:(MethodCall / FieldAccess / Index / String / RawString / F
     }, nil
 }
 
+Ternary = cond:Expr _ '?' _ ifTrue:Value _ ':' _ elseVal:Value {
+    return ast.Ternary{
+        Condition: cond.(ast.Node),
+        IfTrue:    ifTrue.(ast.Node),
+        Else:      elseVal.(ast.Node),
+    }, nil
+}
+
 MethodCall = value:Value '.' name:Ident params:ParamList {
     return ast.MethodCall{
         Value:    value.(ast.Node),