wrote dsl for ast boiler plate generation

ast/gen/transpile.go

@@ -0,0 +1,146 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/format"
+	"text/template"
+)
+
+type defTmplData struct {
+	DefName string
+	Name    string
+	Fields  []string
+}
+
+type transpiler struct {
+	Name            string
+	DefinitionNames []string
+	Definitions     []string
+	astDefsTmpl     *template.Template
+	defTmpl         *template.Template
+}
+
+var astDefinitionsTemplate = `
+{{ $name := .Name }}
+package ast
+
+// THIS FILE WAS AUTOMATICALLY GENERATED, DO NOT MANUALLY EDIT
+
+import "git.red-panda.pet/pandaware/lox-go/lexer"
+		
+type {{ .Name }}Visitor interface {
+	{{ range .DefinitionNames }}Visit{{ . }}{{ $name }}(v *{{ . }}{{ $name }}) any{{ "\n" }}{{ end }}
+}
+
+type {{ .Name }} interface {
+	Accept(v {{ .Name }}Visitor) any
+}
+
+{{ range .Definitions }}
+{{ . }}
+{{ end }}`
+
+var definitionTemplate = `
+type {{ .DefName }}{{ .Name }} struct {
+	{{ range .Fields }}{{ . }}{{ "\n" }}{{ end }}
+}
+
+func (n *{{ .DefName }}{{ .Name }}) Accept(v {{ .Name }}Visitor) any {
+	return v.Visit{{ .DefName }}{{ .Name }}(n)
+}
+		
+var _ {{ .Name }} = new({{ .DefName }}{{ .Name }})`
+
+// visitASTDefinitionsNode implements visitor.
+func (t *transpiler) visitASTDefinitionsNode(a *astDefinitionsNode) (string, error) {
+	t.Name = a.name
+
+	for _, defNode := range a.definitions {
+		def, err := defNode.accept(t)
+		if err != nil {
+			return "", err
+		}
+		t.Definitions = append(t.Definitions, def)
+	}
+
+	buf := &bytes.Buffer{}
+	err := t.astDefsTmpl.Execute(buf, t)
+	return buf.String(), err
+}
+
+// visitDefinition implements visitor.
+func (t *transpiler) visitDefinition(d *definitionNode) (string, error) {
+	name, err := d.identifier.accept(t)
+	if err != nil {
+		return "", err
+	}
+
+	t.DefinitionNames = append(t.DefinitionNames, name)
+
+	fields := make([]string, len(d.fields))
+
+	for _, fieldNode := range d.fields {
+		field, err := fieldNode.accept(t)
+		if err != nil {
+			return "", err
+		}
+		fields = append(fields, field)
+	}
+
+	buf := &bytes.Buffer{}
+
+	err = t.defTmpl.Execute(buf, defTmplData{
+		DefName: name,
+		Name:    t.Name,
+		Fields:  fields,
+	})
+
+	return buf.String(), err
+}
+
+// visitField implements visitor.
+func (t *transpiler) visitField(g *fieldNode) (string, error) {
+	left, err := g.left.accept(t)
+	if err != nil {
+		return "", err
+	}
+
+	right, err := g.right.accept(t)
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("\t%s\t%s\n", left, right), nil
+}
+
+// visitIdentifier implements visitor.
+func (t *transpiler) visitIdentifier(i *identifierNode) (string, error) {
+	return i.value, nil
+}
+
+// visitName implements visitor.
+func (t *transpiler) visitName(n *nameNode) (string, error) {
+	return n.value, nil
+}
+
+var _ visitor = new(transpiler)
+
+func transpile(n node) (string, []byte, error) {
+	var err error
+	t := new(transpiler)
+
+	t.Definitions = []string{}
+	t.DefinitionNames = []string{}
+
+	t.astDefsTmpl, err = template.New("").Parse(astDefinitionsTemplate)
+	t.defTmpl, err = template.New("").Parse(definitionTemplate)
+
+	str, err := n.accept(t)
+	if err != nil {
+		return "", nil, err
+	}
+
+	bs, err := format.Source([]byte(str))
+	return t.Name, bs, err
+}