implement compiling default arguments

Author: itchyny

ast/node.go

@@ -65,6 +65,7 @@ type Function struct {
 	Body        []Statement  // function body
 	Name        Expr         // function name
 	Params      []*Ident     // parameters
+	DefaultArgs []Expr       // default arguments
 	Attr        FuncAttr     // function attributes
 	EndFunction *EndFunction // :endfunction
 }

compiler/compiler.go

@@ -153,13 +153,22 @@ func (c *Compiler) compileFunction(node *ast.Function) {
 	if len(node.Params) > 0 {
 		c.fprint(" ")
 		ps := make([]string, 0, len(node.Params))
-		for _, p := range node.Params {
-			if p.Name == token.DOTDOTDOT.String() {
-				ps = append(ps, ". ...")
-			} else {
+		var remaining bool
+		if node.Params[len(node.Params)-1].Name == token.DOTDOTDOT.String() {
+			node.Params = node.Params[:len(node.Params)-1]
+			remaining = true
+		}
+		for i, p := range node.Params {
+			if i < len(node.Params)-len(node.DefaultArgs) {
 				ps = append(ps, p.Name)
+			} else {
+				ps = append(ps, fmt.Sprintf("(%s %s)", p.Name,
+					c.compileExpr(node.DefaultArgs[i+len(node.DefaultArgs)-len(node.Params)])))
 			}
 		}
+		if remaining {
+			ps = append(ps, ". ...")
+		}
 		c.fprint("%s", strings.Join(ps, " "))
 	}
 	c.fprintln(")")

go/export.go

@@ -69,6 +69,7 @@ func newAstNode(n *VimNode, filename string) ast.Node {
 			Body:        newBody(*n, filename),
 			Name:        newExprNode(n.left, filename),
 			Params:      newIdents(*n, filename),
+			DefaultArgs: newExprs(n.default_args, filename),
 			Attr:        attr,
 			EndFunction: newAstNode(n.endfunction, filename).(*ast.EndFunction),
 		}
@@ -605,6 +606,19 @@ func newList(n VimNode, filename string) []ast.Expr {
 	return list
 }
 
+func newExprs(xs []*VimNode, filename string) []ast.Expr {
+	var list []ast.Expr
+	if xs != nil {
+		list = make([]ast.Expr, 0, len(xs))
+	}
+	for _, node := range xs {
+		if node != nil { // conservative
+			list = append(list, newExprNode(node, filename))
+		}
+	}
+	return list
+}
+
 func newValues(n VimNode, filename string) []ast.Expr {
 	var values []ast.Expr
 	for _, v := range n.value.([]interface{}) {