traefik/cmd/internal/gen/centrifuge.go
2021-07-15 15:58:08 +02:00

347 lines
6.5 KiB
Go

package main
import (
"bytes"
"fmt"
"go/format"
"go/importer"
"go/token"
"go/types"
"io"
"log"
"os"
"path"
"path/filepath"
"reflect"
"sort"
"strings"
"golang.org/x/tools/imports"
)
// File a kind of AST element that represents a file.
type File struct {
Package string
Imports []string
Elements []Element
}
// Element is a simplified version of a symbol.
type Element struct {
Name string
Value string
}
// Centrifuge a centrifuge.
// Generate Go Structures from Go structures.
type Centrifuge struct {
IncludedImports []string
ExcludedTypes []string
ExcludedFiles []string
TypeCleaner func(types.Type, string) string
PackageCleaner func(string) string
rootPkg string
fileSet *token.FileSet
pkg *types.Package
}
// NewCentrifuge creates a new Centrifuge.
func NewCentrifuge(rootPkg string) (*Centrifuge, error) {
fileSet := token.NewFileSet()
pkg, err := importer.ForCompiler(fileSet, "source", nil).Import(rootPkg)
if err != nil {
return nil, err
}
return &Centrifuge{
fileSet: fileSet,
pkg: pkg,
rootPkg: rootPkg,
TypeCleaner: func(typ types.Type, _ string) string {
return typ.String()
},
PackageCleaner: func(s string) string {
return s
},
}, nil
}
// Run runs the code extraction and the code generation.
func (c Centrifuge) Run(dest string, pkgName string) error {
files, err := c.run(c.pkg.Scope(), c.rootPkg, pkgName)
if err != nil {
return err
}
err = fileWriter{baseDir: dest}.Write(files)
if err != nil {
return err
}
for _, p := range c.pkg.Imports() {
if contains(c.IncludedImports, p.Path()) {
fls, err := c.run(p.Scope(), p.Path(), p.Name())
if err != nil {
return err
}
err = fileWriter{baseDir: filepath.Join(dest, p.Name())}.Write(fls)
if err != nil {
return err
}
}
}
return err
}
func (c Centrifuge) run(sc *types.Scope, rootPkg string, pkgName string) (map[string]*File, error) {
files := map[string]*File{}
for _, name := range sc.Names() {
if contains(c.ExcludedTypes, name) {
continue
}
o := sc.Lookup(name)
if !o.Exported() {
continue
}
filename := filepath.Base(c.fileSet.File(o.Pos()).Name())
if contains(c.ExcludedFiles, path.Join(rootPkg, filename)) {
continue
}
fl, ok := files[filename]
if !ok {
files[filename] = &File{Package: pkgName}
fl = files[filename]
}
elt := Element{
Name: name,
}
switch ob := o.(type) {
case *types.TypeName:
switch obj := ob.Type().(*types.Named).Underlying().(type) {
case *types.Struct:
elt.Value = c.writeStruct(name, obj, rootPkg, fl)
case *types.Map:
elt.Value = fmt.Sprintf("type %s map[%s]%s\n", name, obj.Key().String(), c.TypeCleaner(obj.Elem(), rootPkg))
case *types.Slice:
elt.Value = fmt.Sprintf("type %s []%v\n", name, c.TypeCleaner(obj.Elem(), rootPkg))
case *types.Basic:
elt.Value = fmt.Sprintf("type %s %v\n", name, obj.Name())
default:
log.Printf("OTHER TYPE::: %s %T\n", name, o.Type().(*types.Named).Underlying())
continue
}
default:
log.Printf("OTHER::: %s %T\n", name, o)
continue
}
if len(elt.Value) > 0 {
fl.Elements = append(fl.Elements, elt)
}
}
return files, nil
}
func (c Centrifuge) writeStruct(name string, obj *types.Struct, rootPkg string, elt *File) string {
b := strings.Builder{}
b.WriteString(fmt.Sprintf("type %s struct {\n", name))
for i := 0; i < obj.NumFields(); i++ {
field := obj.Field(i)
if !field.Exported() {
continue
}
fPkg := c.PackageCleaner(extractPackage(field.Type()))
if fPkg != "" && fPkg != rootPkg {
elt.Imports = append(elt.Imports, fPkg)
}
fType := c.TypeCleaner(field.Type(), rootPkg)
if field.Embedded() {
b.WriteString(fmt.Sprintf("\t%s\n", fType))
continue
}
values, ok := lookupTagValue(obj.Tag(i), "json")
if len(values) > 0 && values[0] == "-" {
continue
}
b.WriteString(fmt.Sprintf("\t%s %s", field.Name(), fType))
if ok {
b.WriteString(fmt.Sprintf(" `json:\"%s\"`", strings.Join(values, ",")))
}
b.WriteString("\n")
}
b.WriteString("}\n")
return b.String()
}
func lookupTagValue(raw, key string) ([]string, bool) {
value, ok := reflect.StructTag(raw).Lookup(key)
if !ok {
return nil, ok
}
values := strings.Split(value, ",")
if len(values) < 1 {
return nil, true
}
return values, true
}
func extractPackage(t types.Type) string {
switch tu := t.(type) {
case *types.Named:
return tu.Obj().Pkg().Path()
case *types.Slice:
if v, ok := tu.Elem().(*types.Named); ok {
return v.Obj().Pkg().Path()
}
return ""
case *types.Map:
if v, ok := tu.Elem().(*types.Named); ok {
return v.Obj().Pkg().Path()
}
return ""
case *types.Pointer:
return extractPackage(tu.Elem())
default:
return ""
}
}
func contains(values []string, value string) bool {
for _, val := range values {
if val == value {
return true
}
}
return false
}
type fileWriter struct {
baseDir string
}
func (f fileWriter) Write(files map[string]*File) error {
err := os.MkdirAll(f.baseDir, 0755)
if err != nil {
return err
}
for name, file := range files {
err = f.writeFile(name, file)
if err != nil {
return err
}
}
return nil
}
func (f fileWriter) writeFile(name string, desc *File) error {
if len(desc.Elements) == 0 {
return nil
}
filename := filepath.Join(f.baseDir, name)
file, err := os.Create(filename)
if err != nil {
return fmt.Errorf("failed to create file: %w", err)
}
defer func() { _ = file.Close() }()
b := bytes.NewBufferString("package ")
b.WriteString(desc.Package)
b.WriteString("\n")
b.WriteString("// Code generated by centrifuge. DO NOT EDIT.\n")
b.WriteString("\n")
f.writeImports(b, desc.Imports)
b.WriteString("\n")
for _, elt := range desc.Elements {
b.WriteString(elt.Value)
b.WriteString("\n")
}
// gofmt
source, err := format.Source(b.Bytes())
if err != nil {
log.Println(b.String())
return fmt.Errorf("failed to format sources: %w", err)
}
// goimports
process, err := imports.Process(filename, source, nil)
if err != nil {
log.Println(string(source))
return fmt.Errorf("failed to format imports: %w", err)
}
_, err = file.Write(process)
if err != nil {
return err
}
return nil
}
func (f fileWriter) writeImports(b io.StringWriter, imports []string) {
if len(imports) == 0 {
return
}
uniq := map[string]struct{}{}
sort.Strings(imports)
_, _ = b.WriteString("import (\n")
for _, s := range imports {
if _, exist := uniq[s]; exist {
continue
}
uniq[s] = struct{}{}
_, _ = b.WriteString(fmt.Sprintf(` "%s"`+"\n", s))
}
_, _ = b.WriteString(")\n")
}