Added fallback fs.

ricefs/fs.go

@@ -72,7 +72,7 @@ func (f *RiceFs) Stat(name string) (os.FileInfo, error) {
 	return fBox.Stat()
 }
 
-// Name returns the name of the file system
+// Name returns the name of the file system.
 func (f *RiceFs) Name() string {
 	return "Rice FS"
 }

vfs/fallbackfs.go

@@ -0,0 +1,106 @@
+package vfs
+
+import (
+	"os"
+	"time"
+
+	"github.com/spf13/afero"
+)
+
+var _ afero.Fs = &FallbackFs{}
+
+// FallbackFs presents a source Fs that falls back to a backup Fs when the Fs call fails.
+type FallbackFs struct {
+	source afero.Fs
+	backup afero.Fs
+}
+
+// NewFallbackFs creates a new FallbackFs
+func NewFallbackFs(source, backup afero.Fs) *FallbackFs {
+	return &FallbackFs{source, backup}
+}
+
+func (f *FallbackFs) do(action func(afero.Fs) error) error {
+	err := action(f.source)
+	if err == nil {
+		return nil
+	}
+	return action(f.backup)
+}
+
+func (f *FallbackFs) doFile(action func(afero.Fs) (afero.File, error)) (afero.File, error) {
+	file, err := action(f.source)
+	if err == nil {
+		return file.(afero.File), nil
+	}
+	return action(f.backup)
+}
+
+func (f *FallbackFs) doFileInfo(action func(afero.Fs) (os.FileInfo, error)) (os.FileInfo, error) {
+	res, err := action(f.source)
+	if err == nil {
+		return res, nil
+	}
+	return action(f.backup)
+}
+
+// Create creates a file in the filesystem, returning the file and an error, if any happens.
+func (f *FallbackFs) Create(name string) (afero.File, error) {
+	return f.doFile(func(fs afero.Fs) (afero.File, error) { return fs.Create(name) })
+}
+
+// Mkdir creates a directory in the filesystem, return an error if any happens.
+func (f *FallbackFs) Mkdir(name string, perm os.FileMode) error {
+	return f.do(func(fs afero.Fs) error { return fs.Mkdir(name, perm) })
+}
+
+// MkdirAll creates a directory path and all parents that does not exist yet.
+func (f *FallbackFs) MkdirAll(path string, perm os.FileMode) error {
+	return f.do(func(fs afero.Fs) error { return fs.MkdirAll(path, perm) })
+}
+
+// Open opens a file, returning it or an error, if any happens.
+func (f *FallbackFs) Open(name string) (afero.File, error) {
+	return f.doFile(func(fs afero.Fs) (afero.File, error) { return fs.Open(name) })
+}
+
+// OpenFile opens a file using the given flags and the given mode.
+func (f *FallbackFs) OpenFile(name string, flag int, perm os.FileMode) (afero.File, error) {
+	return f.doFile(func(fs afero.Fs) (afero.File, error) { return fs.OpenFile(name, flag, perm) })
+}
+
+// Remove removes a file identified by name, returning an error, if any happens.
+func (f *FallbackFs) Remove(name string) error {
+
+	return f.do(func(fs afero.Fs) error { return fs.Remove(name) })
+}
+
+// RemoveAll removes a directory path and any children it contains. It does not fail if the path does not exist (return nil).
+func (f *FallbackFs) RemoveAll(path string) error {
+	return f.do(func(fs afero.Fs) error { return fs.RemoveAll(path) })
+}
+
+// Rename renames a file.
+func (f *FallbackFs) Rename(oldname, newname string) error {
+	return f.do(func(fs afero.Fs) error { return fs.Rename(oldname, newname) })
+}
+
+// Stat returns a FileInfo describing the named file, or an error, if any happens.
+func (f *FallbackFs) Stat(name string) (os.FileInfo, error) {
+	return f.doFileInfo(func(fs afero.Fs) (os.FileInfo, error) { return fs.Stat(name) })
+}
+
+// Name returns the name of the file system.
+func (f *FallbackFs) Name() string {
+	return "Fallback FS"
+}
+
+// Chmod changes the mode of the named file to mode.
+func (f *FallbackFs) Chmod(name string, mode os.FileMode) error {
+	return f.do(func(fs afero.Fs) error { return fs.Chmod(name, mode) })
+}
+
+// Chtimes changes the access and modification times of the named file.
+func (f *FallbackFs) Chtimes(name string, atime time.Time, mtime time.Time) error {
+	return f.do(func(fs afero.Fs) error { return fs.Chtimes(name, atime, mtime) })
+}