Allow Close on dirs, make sure errors make sense

file.go

@@ -15,11 +15,10 @@ var (
 
 // File is an interface that provides functionality for handling
 // files/directories as values that can be supplied to commands. For
-// directories, child files are accessed serially by calling `Files()`
-// or `Walk()`.
+// directories, child files are accessed serially by calling `NextFile()`
 //
-// Read/Seek/Close methods are only valid for files
-// Files/Walk methods are only valid for directories
+// Read/Seek methods are only valid for files
+// NextFile method is only valid for directories
 type File interface {
 	io.Reader
 	io.Closer
@@ -37,14 +36,24 @@ type File interface {
 	// directory). It will return io.EOF if no more files are
 	// available. If the file is a regular file (not a directory), NextFile
 	// will return a non-nil error.
+	//
+	// Note:
+	// - Some implementations may only allow reading in order - if a
+	//   child directory is returned, you need to read all it's children
+	//   first before calling NextFile on parent again. Before doing parallel
+	//   reading or reading entire level at once, make sure the implementation
+	//   you are using allows that
+	// - Returned files may not be sorted
+	// - Depending on implementation it may not be safe to iterate multiple
+	//   children in parallel
 	NextFile() (string, File, error)
 }
 
 // FileInfo exposes information on files in local filesystem
 type FileInfo interface {
 	File
 
-	// AbsPath returns full/real file path.
+	// AbsPath returns full real file path.
 	AbsPath() string
 
 	// Stat returns os.Stat of this file

file_test.go

@@ -22,12 +22,12 @@ func TestSliceFiles(t *testing.T) {
 		t.Fatal("SliceFile should always be a directory")
 	}
 
-	if n, err := sf.Read(buf); n > 0 || err != io.EOF {
+	if n, err := sf.Read(buf); n > 0 || err != ErrNotReader {
 		t.Fatal("Shouldn't be able to read data from a SliceFile")
 	}
 
-	if err := sf.Close(); err != ErrNotReader {
-		t.Fatal("Shouldn't be able to call `Close` on a SliceFile")
+	if err := sf.Close(); err != nil {
+		t.Fatal("Should be able to call `Close` on a SliceFile")
 	}
 
 	_, file, err := sf.NextFile()
@@ -151,8 +151,8 @@ anotherfile
 	if n, err := mpf.Read(buf); n > 0 || err != ErrNotReader {
 		t.Fatal("Shouldn't be able to call `Read` on a directory")
 	}
-	if err := mpf.Close(); err != ErrNotReader {
-		t.Fatal("Shouldn't be able to call `Close` on a directory")
+	if err := mpf.Close(); err != nil {
+		t.Fatal("Should be able to call `Close` on a directory")
 	}
 
 	// test properties of file created from third part (nested file)

multifilereader.go

@@ -20,7 +20,7 @@ type MultiFileReader struct {
 	files []File
 	path  []string
 
-	currentFile io.Reader
+	currentFile File
 	buf         bytes.Buffer
 	mpWriter    *multipart.Writer
 	closed      bool
@@ -121,7 +121,11 @@ func (mfr *MultiFileReader) Read(buf []byte) (written int, err error) {
 
 	// otherwise, read from file data
 	written, err = mfr.currentFile.Read(buf)
-	if err == io.EOF {
+	if err == io.EOF || err == ErrNotReader {
+		if err := mfr.currentFile.Close(); err != nil {
+			return written, err
+		}
+
 		mfr.currentFile = nil
 		return written, nil
 	}

multipartfile.go

@@ -136,21 +136,18 @@ func (f *MultipartFile) Read(p []byte) (int, error) {
 }
 
 func (f *MultipartFile) Close() error {
-	if f.IsDirectory() {
-		return ErrNotReader
-	}
 	return f.Part.Close()
 }
 
 func (f *MultipartFile) Seek(offset int64, whence int) (int64, error) {
 	if f.IsDirectory() {
 		return 0, ErrNotReader
 	}
-	return 0, ErrNotReader
+	return 0, ErrNotSupported
 }
 
 func (f *MultipartFile) Size() (int64, error) {
-	return 0, ErrNotReader
+	return 0, ErrNotSupported
 }
 
 type PartReader interface {

readerfile.go

@@ -1,7 +1,6 @@
 package files
 
 import (
-	"errors"
 	"io"
 	"os"
 	"path/filepath"
@@ -54,7 +53,7 @@ func (f *ReaderFile) Stat() os.FileInfo {
 
 func (f *ReaderFile) Size() (int64, error) {
 	if f.stat == nil {
-		return 0, errors.New("file size unknown")
+		return 0, ErrNotSupported
 	}
 	return f.stat.Size(), nil
 }

serialfile.go

@@ -98,7 +98,7 @@ func (f *serialFile) NextFile() (string, File, error) {
 }
 
 func (f *serialFile) Read(p []byte) (int, error) {
-	return 0, io.EOF
+	return 0, ErrNotReader
 }
 
 func (f *serialFile) Close() error {

slicefile.go

@@ -35,11 +35,11 @@ func (f *SliceFile) NextFile() (string, File, error) {
 }
 
 func (f *SliceFile) Read(p []byte) (int, error) {
-	return 0, io.EOF
+	return 0, ErrNotReader
 }
 
 func (f *SliceFile) Close() error {
-	return ErrNotReader
+	return nil
 }
 
 func (f *SliceFile) Seek(offset int64, whence int) (int64, error) {