Respond to feedback; make fsys separate from Archive

Author: earthboundkid

txtar/archive.go

@@ -34,6 +34,7 @@ package txtar
 import (
 	"bytes"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"strings"
 )
@@ -138,3 +139,8 @@ func fixNL(data []byte) []byte {
 	d[len(data)] = '\n'
 	return d
 }
+
+// FS returns an fs.FS that reads from the Archive.
+func (a *Archive) FS() fs.FS {
+	return fsys{a}
+}

txtar/fs.go

@@ -1,9 +1,7 @@
-// Copyright 2021 The Go Authors. All rights reserved.
+// Copyright 2022 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.
 
-// +build go1.16
-
 package txtar
 
 import (
@@ -16,10 +14,12 @@ import (
 	"time"
 )
 
-var _ fs.FS = (*Archive)(nil)
+type fsys struct {
+	*Archive
+}
 
 // Open implements fs.FS.
-func (a *Archive) Open(name string) (fs.File, error) {
+func (a fsys) Open(name string) (fs.File, error) {
 	if !fs.ValidPath(name) {
 		return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrNotExist}
 	}
@@ -65,10 +65,10 @@ func (a *Archive) Open(name string) (fs.File, error) {
 	return &openDir{newDirInfo(name), entries, 0}, nil
 }
 
-var _ fs.ReadFileFS = (*Archive)(nil)
+var _ fs.ReadFileFS = fsys{}
 
 // ReadFile implements fs.ReadFileFS.
-func (a *Archive) ReadFile(name string) ([]byte, error) {
+func (a fsys) ReadFile(name string) ([]byte, error) {
 	if !fs.ValidPath(name) {
 		return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrNotExist}
 	}
@@ -165,8 +165,9 @@ func (d *openDir) ReadDir(count int) ([]fs.DirEntry, error) {
 //
 // The transformation is lossy.
 // For example, because directories are implicit in txtar archives,
-// empty directories in fsys will be lost, and txtar does not represent file mode, mtime, or other file metadata.
-// From does not guarantee that a.File[i].Data contain no file marker lines.
+// empty directories in fsys will be lost,
+// and txtar does not represent file mode, mtime, or other file metadata.
+// From does not guarantee that a.File[i].Data contains no file marker lines.
 // See also warnings on Format.
 // In short, it is unwise to use txtar as a generic filesystem serialization mechanism.
 func From(fsys fs.FS) (*Archive, error) {

txtar/fs_test.go

@@ -68,15 +68,16 @@ two
 		t.Run(tc.name, func(t *testing.T) {
 			a := Parse([]byte(tc.input))
 			files := strings.Fields(tc.files)
-			if err := fstest.TestFS(a, files...); err != nil {
+			if err := fstest.TestFS(a.FS(), files...); err != nil {
 				t.Fatal(err)
 			}
 			for _, name := range files {
 				for _, f := range a.Files {
 					if f.Name != name {
 						continue
 					}
-					b, err := fs.ReadFile(a, name)
+					fsys := a.FS()
+					b, err := fs.ReadFile(fsys, name)
 					if err != nil {
 						t.Fatal(err)
 					}
@@ -85,7 +86,7 @@ two
 					}
 					// Be careful with n cases, this open is O(n^3) deep
 					// Do iotest
-					fsfile, err := a.Open(name)
+					fsfile, err := fsys.Open(name)
 					if err != nil {
 						t.Fatal(err)
 					}
@@ -96,7 +97,7 @@ two
 						t.Fatal(err)
 					}
 					// test io.Copy
-					fsfile, err = a.Open(name)
+					fsfile, err = fsys.Open(name)
 					if err != nil {
 						t.Fatal(err)
 					}
@@ -116,7 +117,7 @@ two
 					}
 				}
 			}
-			a2, err := From(a)
+			a2, err := From(a.FS())
 			if err != nil {
 				t.Fatalf("failed to write fsys for %v: %v", tc.name, err)
 			}