Merge pull request #34 from haya14busa/printer

printer: add printer package

Author: haya14busa

printer/printer.go

@@ -0,0 +1,92 @@
+// Package printer implements printing of AST nodes.
+//
+// This is WIP package. DO NOT USE.
+package printer
+
+import (
+	"errors"
+	"fmt"
+	"io"
+
+	"github.com/haya14busa/go-vimlparser/ast"
+)
+
+// A Config node controls the output of Fprint.
+type Config struct{}
+
+// Fprint "pretty-prints" an AST node to output for a given configuration cfg.
+func Fprint(output io.Writer, node ast.Node, cfg *Config) error {
+	var p printer
+	p.init(cfg)
+	if err := p.printNode(node); err != nil {
+		return err
+	}
+	if _, err := output.Write(p.output); err != nil {
+		return err
+	}
+	return nil
+}
+
+type printer struct {
+	Config
+
+	// Current state
+	output []byte // raw printer result
+}
+
+func (p *printer) init(cfg *Config) {
+	if cfg != nil {
+		p.Config = *cfg
+	}
+}
+
+func (p *printer) writeString(s string) {
+	p.output = append(p.output, s...)
+}
+
+func (p *printer) printNode(node ast.Node) error {
+	switch n := node.(type) {
+	case *ast.File:
+		return p.file(n)
+	case ast.Expr:
+		return p.expr(n)
+	case ast.Statement:
+		return p.stmt(n)
+	default:
+		return fmt.Errorf("go-vimlparser/printer: unsupported node type %T", node)
+	}
+}
+
+func (p *printer) file(f *ast.File) error {
+	return errors.New("Not implemented: printer.file")
+}
+
+func (p *printer) expr(expr ast.Expr) error {
+	switch n := expr.(type) {
+	// case *ast.TernaryExpr:
+	// case *ast.BinaryExpr:
+	// case *ast.UnaryExpr:
+	// case *ast.SubscriptExpr:
+	// case *ast.SliceExpr:
+	// case *ast.CallExpr:
+	// case *ast.DotExpr:
+	// case *ast.List:
+	// case *ast.Dict:
+	// case *ast.CurlyName:
+	// case *ast.CurlyNameLit:
+	// case *ast.CurlyNameExpr:
+	case *ast.BasicLit:
+		p.writeString(n.Value)
+	case *ast.Ident:
+		p.writeString(n.Name)
+	// case *ast.LambdaExpr:
+	// case *ast.ParenExpr:
+	default:
+		return fmt.Errorf("unsupported expr type %T", n)
+	}
+	return nil
+}
+
+func (p *printer) stmt(node ast.Statement) error {
+	return errors.New("Not implemented: printer.stmt")
+}

printer/printer_test.go

@@ -0,0 +1,53 @@
+package printer
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+
+	"github.com/haya14busa/go-vimlparser"
+)
+
+func TestFprint_file(t *testing.T) {
+	src := `let _ = 1`
+	r := strings.NewReader(src)
+	node, err := vimlparser.ParseFile(r, "", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	buf := new(bytes.Buffer)
+	if err := Fprint(buf, node, nil); err == nil {
+		t.Error("want error")
+	}
+}
+
+func TestFprint_expr(t *testing.T) {
+	tests := []struct {
+		in      string
+		want    string
+		wantErr bool
+	}{
+		{in: `xyz`, want: `xyz`},                       // Ident
+		{in: `"double quote"`, want: `"double quote"`}, // BasicLit
+		{in: `14`, want: `14`},                         // BasicLit
+		{in: `x+1`, want: `x + 1`, wantErr: true},
+	}
+
+	for _, tt := range tests {
+		r := strings.NewReader(tt.in)
+		node, err := vimlparser.ParseExpr(r)
+		if err != nil {
+			t.Fatal(err)
+		}
+		buf := new(bytes.Buffer)
+		if err := Fprint(buf, node, nil); err != nil {
+			if !tt.wantErr {
+				t.Errorf("got unexpected error: %v", err)
+			}
+			continue
+		}
+		if got := buf.String(); got != tt.want {
+			t.Errorf("got: %v, want: %v", got, tt.want)
+		}
+	}
+}