Init project as clone of gonew package

Author: anilsenay

cmd/gonew.go

@@ -0,0 +1,233 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Gonew starts a new Go module by copying a template module.
+//
+// Usage:
+//
+//	gonew srcmod[@version] [dstmod [dir]]
+//
+// Gonew makes a copy of the srcmod module, changing its module path to dstmod.
+// It writes that new module to a new directory named by dir.
+// If dir already exists, it must be an empty directory.
+// If dir is omitted, gonew uses ./elem where elem is the final path element of dstmod.
+//
+// This command is highly experimental and subject to change.
+//
+// # Example
+//
+// To install gonew:
+//
+//	go install golang.org/x/tools/cmd/gonew@latest
+//
+// To clone the basic command-line program template golang.org/x/example/hello
+// as your.domain/myprog, in the directory ./myprog:
+//
+//	gonew golang.org/x/example/hello your.domain/myprog
+//
+// To clone the latest copy of the rsc.io/quote module, keeping that module path,
+// into ./quote:
+//
+//	gonew rsc.io/quote
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"go/parser"
+	"go/token"
+	"io/fs"
+	"log"
+	"os"
+	"os/exec"
+	"path"
+	"path/filepath"
+	"strconv"
+	"strings"
+
+	"github.com/anilsenay/gonew/edit"
+	"golang.org/x/mod/modfile"
+	"golang.org/x/mod/module"
+)
+
+func usage() {
+	fmt.Fprintf(os.Stderr, "usage: gonew srcmod[@version] [dstmod [dir]]\n")
+	fmt.Fprintf(os.Stderr, "See https://pkg.go.dev/golang.org/x/tools/cmd/gonew.\n")
+	os.Exit(2)
+}
+
+func main() {
+	log.SetPrefix("gonew: ")
+	log.SetFlags(0)
+	flag.Usage = usage
+	flag.Parse()
+	args := flag.Args()
+
+	if len(args) < 1 || len(args) > 3 {
+		usage()
+	}
+
+	srcMod := args[0]
+	srcModVers := srcMod
+	if !strings.Contains(srcModVers, "@") {
+		srcModVers += "@latest"
+	}
+	srcMod, _, _ = strings.Cut(srcMod, "@")
+	if err := module.CheckPath(srcMod); err != nil {
+		log.Fatalf("invalid source module name: %v", err)
+	}
+
+	dstMod := srcMod
+	if len(args) >= 2 {
+		dstMod = args[1]
+		if err := module.CheckPath(dstMod); err != nil {
+			log.Fatalf("invalid destination module name: %v", err)
+		}
+	}
+
+	var dir string
+	if len(args) == 3 {
+		dir = args[2]
+	} else {
+		dir = "." + string(filepath.Separator) + path.Base(dstMod)
+	}
+
+	// Dir must not exist or must be an empty directory.
+	de, err := os.ReadDir(dir)
+	if err == nil && len(de) > 0 {
+		log.Fatalf("target directory %s exists and is non-empty", dir)
+	}
+	needMkdir := err != nil
+
+	var stdout, stderr bytes.Buffer
+	cmd := exec.Command("go", "mod", "download", "-json", srcModVers)
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+	if err := cmd.Run(); err != nil {
+		log.Fatalf("go mod download -json %s: %v\n%s%s", srcModVers, err, stderr.Bytes(), stdout.Bytes())
+	}
+
+	var info struct {
+		Dir string
+	}
+	if err := json.Unmarshal(stdout.Bytes(), &info); err != nil {
+		log.Fatalf("go mod download -json %s: invalid JSON output: %v\n%s%s", srcMod, err, stderr.Bytes(), stdout.Bytes())
+	}
+
+	if needMkdir {
+		if err := os.MkdirAll(dir, 0777); err != nil {
+			log.Fatal(err)
+		}
+	}
+
+	// Copy from module cache into new directory, making edits as needed.
+	filepath.WalkDir(info.Dir, func(src string, d fs.DirEntry, err error) error {
+		if err != nil {
+			log.Fatal(err)
+		}
+		rel, err := filepath.Rel(info.Dir, src)
+		if err != nil {
+			log.Fatal(err)
+		}
+		dst := filepath.Join(dir, rel)
+		if d.IsDir() {
+			if err := os.MkdirAll(dst, 0777); err != nil {
+				log.Fatal(err)
+			}
+			return nil
+		}
+
+		data, err := os.ReadFile(src)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		isRoot := !strings.Contains(rel, string(filepath.Separator))
+		if strings.HasSuffix(rel, ".go") {
+			data = fixGo(data, rel, srcMod, dstMod, isRoot)
+		}
+		if rel == "go.mod" {
+			data = fixGoMod(data, srcMod, dstMod)
+		}
+
+		if err := os.WriteFile(dst, data, 0666); err != nil {
+			log.Fatal(err)
+		}
+		return nil
+	})
+
+	log.Printf("initialized %s in %s", dstMod, dir)
+}
+
+// fixGo rewrites the Go source in data to replace srcMod with dstMod.
+// isRoot indicates whether the file is in the root directory of the module,
+// in which case we also update the package name.
+func fixGo(data []byte, file string, srcMod, dstMod string, isRoot bool) []byte {
+	fset := token.NewFileSet()
+	f, err := parser.ParseFile(fset, file, data, parser.ImportsOnly)
+	if err != nil {
+		log.Fatalf("parsing source module:\n%s", err)
+	}
+
+	buf := edit.NewBuffer(data)
+	at := func(p token.Pos) int {
+		return fset.File(p).Offset(p)
+	}
+
+	srcName := path.Base(srcMod)
+	dstName := path.Base(dstMod)
+	if isRoot {
+		if name := f.Name.Name; name == srcName || name == srcName+"_test" {
+			dname := dstName + strings.TrimPrefix(name, srcName)
+			if !token.IsIdentifier(dname) {
+				log.Fatalf("%s: cannot rename package %s to package %s: invalid package name", file, name, dname)
+			}
+			buf.Replace(at(f.Name.Pos()), at(f.Name.End()), dname)
+		}
+	}
+
+	for _, spec := range f.Imports {
+		path, err := strconv.Unquote(spec.Path.Value)
+		if err != nil {
+			continue
+		}
+		if path == srcMod {
+			if srcName != dstName && spec.Name == nil {
+				// Add package rename because source code uses original name.
+				// The renaming looks strange, but template authors are unlikely to
+				// create a template where the root package is imported by packages
+				// in subdirectories, and the renaming at least keeps the code working.
+				// A more sophisticated approach would be to rename the uses of
+				// the package identifier in the file too, but then you have to worry about
+				// name collisions, and given how unlikely this is, it doesn't seem worth
+				// trying to clean up the file that way.
+				buf.Insert(at(spec.Path.Pos()), srcName+" ")
+			}
+			// Change import path to dstMod
+			buf.Replace(at(spec.Path.Pos()), at(spec.Path.End()), strconv.Quote(dstMod))
+		}
+		if strings.HasPrefix(path, srcMod+"/") {
+			// Change import path to begin with dstMod
+			buf.Replace(at(spec.Path.Pos()), at(spec.Path.End()), strconv.Quote(strings.Replace(path, srcMod, dstMod, 1)))
+		}
+	}
+	return buf.Bytes()
+}
+
+// fixGoMod rewrites the go.mod content in data to replace srcMod with dstMod
+// in the module path.
+func fixGoMod(data []byte, srcMod, dstMod string) []byte {
+	f, err := modfile.ParseLax("go.mod", data, nil)
+	if err != nil {
+		log.Fatalf("parsing source module:\n%s", err)
+	}
+	f.AddModuleStmt(dstMod)
+	new, err := f.Format()
+	if err != nil {
+		return data
+	}
+	return new
+}

edit/edit.go

@@ -0,0 +1,96 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package edit implements buffered position-based editing of byte slices.
+package edit
+
+import (
+	"fmt"
+	"sort"
+)
+
+// A Buffer is a queue of edits to apply to a given byte slice.
+type Buffer struct {
+	old []byte
+	q   edits
+}
+
+// An edit records a single text modification: change the bytes in [start,end) to new.
+type edit struct {
+	start int
+	end   int
+	new   string
+}
+
+// An edits is a list of edits that is sortable by start offset, breaking ties by end offset.
+type edits []edit
+
+func (x edits) Len() int      { return len(x) }
+func (x edits) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
+func (x edits) Less(i, j int) bool {
+	if x[i].start != x[j].start {
+		return x[i].start < x[j].start
+	}
+	return x[i].end < x[j].end
+}
+
+// NewBuffer returns a new buffer to accumulate changes to an initial data slice.
+// The returned buffer maintains a reference to the data, so the caller must ensure
+// the data is not modified until after the Buffer is done being used.
+func NewBuffer(old []byte) *Buffer {
+	return &Buffer{old: old}
+}
+
+// Insert inserts the new string at old[pos:pos].
+func (b *Buffer) Insert(pos int, new string) {
+	if pos < 0 || pos > len(b.old) {
+		panic("invalid edit position")
+	}
+	b.q = append(b.q, edit{pos, pos, new})
+}
+
+// Delete deletes the text old[start:end].
+func (b *Buffer) Delete(start, end int) {
+	if end < start || start < 0 || end > len(b.old) {
+		panic("invalid edit position")
+	}
+	b.q = append(b.q, edit{start, end, ""})
+}
+
+// Replace replaces old[start:end] with new.
+func (b *Buffer) Replace(start, end int, new string) {
+	if end < start || start < 0 || end > len(b.old) {
+		panic("invalid edit position")
+	}
+	b.q = append(b.q, edit{start, end, new})
+}
+
+// Bytes returns a new byte slice containing the original data
+// with the queued edits applied.
+func (b *Buffer) Bytes() []byte {
+	// Sort edits by starting position and then by ending position.
+	// Breaking ties by ending position allows insertions at point x
+	// to be applied before a replacement of the text at [x, y).
+	sort.Stable(b.q)
+
+	var new []byte
+	offset := 0
+	for i, e := range b.q {
+		if e.start < offset {
+			e0 := b.q[i-1]
+			panic(fmt.Sprintf("overlapping edits: [%d,%d)->%q, [%d,%d)->%q", e0.start, e0.end, e0.new, e.start, e.end, e.new))
+		}
+		new = append(new, b.old[offset:e.start]...)
+		offset = e.end
+		new = append(new, e.new...)
+	}
+	new = append(new, b.old[offset:]...)
+	return new
+}
+
+// String returns a string containing the original data
+// with the queued edits applied.
+func (b *Buffer) String() string {
+	return string(b.Bytes())
+}

go.mod

@@ -0,0 +1,5 @@
+module github.com/anilsenay/gonew
+
+go 1.21.0
+
+require golang.org/x/mod v0.12.0

go.sum

@@ -0,0 +1,2 @@
+golang.org/x/mod v0.12.0 h1:rmsUpXtvNzj340zd98LZ4KntptpfRHwpFOHG188oHXc=
+golang.org/x/mod v0.12.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=