Tool for rewriting import paths safely.

go.mod

module rename-imports

go 1.13

require golang.org/x/tools v0.0.0-20191224055732-dd894d0a8a40

go.sum

golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
golang.org/x/mod v0.1.1-0.20191105210325-c90efee705ee/go.mod h1:QqPTAvyqsEbceGzBzNggFXnrqF1CaUcvgkdR5Ot7KZg=
golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
golang.org/x/tools v0.0.0-20191224055732-dd894d0a8a40 h1:UyP2XDSgSc8ldYCxAK735zQxeH3Gd81sK7Iy7AoaVxk=
golang.org/x/tools v0.0.0-20191224055732-dd894d0a8a40/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

main.go

package main

import (
	"bytes"
	"flag"
	"fmt"
	"go/parser"
	"go/printer"
	"go/token"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"strings"

	"golang.org/x/tools/go/ast/astutil"
)

type Rules []Rule

type Rule struct{ From, To string }

func ParseRule(s string) (Rule, error) {
	tk := strings.SplitN(s, "=>", 2)
	if len(tk) != 2 {
		return Rule{}, fmt.Errorf("invalid rule %q", s)
	}
	return Rule{
		From: strings.TrimSpace(tk[0]),
		To:   strings.TrimSpace(tk[1]),
	}, nil
}

func (r Rule) String() string { return r.From + "=>" + r.To }

func (rs *Rules) String() string {
	var b strings.Builder
	for i, r := range *rs {
		if i > 0 {
			b.WriteByte(';')
		}
		b.WriteString(r.String())
	}
	return b.String()
}

func (rs *Rules) Set(xs string) error {
	for _, x := range strings.Split(xs, ";") {
		r, err := ParseRule(x)
		if err != nil {
			return err
		}
		*rs = append(*rs, r)
	}
	return nil
}

func main() {
	var rules Rules
	flag.Var(&rules, "r", "rewrite rule")
	flag.Parse()

	if len(rules) == 0 {
		log.Fatal("rules not specified")
	}

	err := filepath.Walk(flag.Arg(0), func(path string, info os.FileInfo, err error) error {
		if filepath.Base(path) == ".git" {
			return filepath.SkipDir
		}
		if err != nil || info.IsDir() {
			return nil
		}
		if filepath.Ext(path) != ".go" {
			return nil
		}

		fset := token.NewFileSet()
		f, err := parser.ParseFile(fset, path, nil, parser.ParseComments)
		if err != nil {
			return err
		}

		rewrote := false
		for _, rule := range rules {
			if astutil.RewriteImport(fset, f, rule.From, rule.To) {
				rewrote = true
			}
		}

		if rewrote {
			var buf bytes.Buffer
			if err := printer.Fprint(&buf, fset, f); err != nil {
				return err
			}

			tokfile := fset.File(f.Pos())
			if err := ioutil.WriteFile(tokfile.Name(), buf.Bytes(), 0755); err != nil {
				return err
			}
			log.Println("renamed", tokfile.Name())
		}

		return nil
	})
	if err != nil {
		log.Fatal(err)
	}
}