archive/zip: add AddFS method to zip Writer

The method AddFS can be used to add the contents of a fs.FS filesystem
to a zip archive.
This method walks the directory tree starting at the root of the filesystem
and adds each file to the archive.

Fixes #54898

Change-Id: I80511cbd91a1d7e09ee52d2d1b09fb5eed25f45f
GitHub-Last-Rev: 1e17f2e6ba
GitHub-Pull-Request: golang/go#61602
Reviewed-on: https://go-review.googlesource.com/c/go/+/513438
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>

api/next/54898.txt

@@ -0,0 +1 @@
+pkg archive/zip, method (*Writer) AddFS(fs.FS) error #54898

src/archive/zip/writer.go

@@ -11,6 +11,7 @@ import (
 	"hash"
 	"hash/crc32"
 	"io"
+	"io/fs"
 	"strings"
 	"unicode/utf8"
 )
@@ -495,6 +496,41 @@ func (w *Writer) RegisterCompressor(method uint16, comp Compressor) {
 	w.compressors[method] = comp
 }
 
+// AddFS adds the files from fs.FS to the archive.
+// It walks the directory tree starting at the root of the filesystem
+// adding each file to the zip using deflate while maintaining the directory structure.
+func (w *Writer) AddFS(fsys fs.FS) error {
+	return fs.WalkDir(fsys, ".", func(name string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() {
+			return nil
+		}
+		info, err := d.Info()
+		if err != nil {
+			return err
+		}
+		h, err := FileInfoHeader(info)
+		if err != nil {
+			return err
+		}
+		h.Name = name
+		h.Method = Deflate
+		fw, err := w.CreateHeader(h)
+		if err != nil {
+			return err
+		}
+		f, err := fsys.Open(name)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		_, err = io.Copy(fw, f)
+		return err
+	})
+}
+
 func (w *Writer) compressor(method uint16) Compressor {
 	comp := w.compressors[method]
 	if comp == nil {

src/archive/zip/writer_test.go

@@ -16,6 +16,7 @@ import (
 	"os"
 	"strings"
 	"testing"
+	"testing/fstest"
 	"time"
 )
 
@@ -602,3 +603,48 @@ func BenchmarkCompressedZipGarbage(b *testing.B) {
 		}
 	})
 }
+
+func writeTestsToFS(tests []WriteTest) fs.FS {
+	fsys := fstest.MapFS{}
+	for _, wt := range tests {
+		fsys[wt.Name] = &fstest.MapFile{
+			Data: wt.Data,
+			Mode: wt.Mode,
+		}
+	}
+	return fsys
+}
+
+func TestWriterAddFS(t *testing.T) {
+	buf := new(bytes.Buffer)
+	w := NewWriter(buf)
+	tests := []WriteTest{
+		{
+			Name: "file.go",
+			Data: []byte("hello"),
+			Mode: 0644,
+		},
+		{
+			Name: "subfolder/another.go",
+			Data: []byte("world"),
+			Mode: 0644,
+		},
+	}
+	err := w.AddFS(writeTestsToFS(tests))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := w.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	// read it back
+	r, err := NewReader(bytes.NewReader(buf.Bytes()), int64(buf.Len()))
+	if err != nil {
+		t.Fatal(err)
+	}
+	for i, wt := range tests {
+		testReadFile(t, r.File[i], &wt)
+	}
+}