return improved errors from MemMapFs methods

MemMapFs.Mkdir now returns an error if the file or dir already exists
MemMapFs.Remove now returns an error if the file or dir doesn't exists

fixes #43

memmap.go

@@ -56,13 +56,10 @@ func (m *MemMapFs) Create(name string) (File, error) {
 	return file, nil
 }
 
-func (m *MemMapFs) unRegisterWithParent(fileName string) {
+func (m *MemMapFs) unRegisterWithParent(fileName string) error {
 	f, err := m.lockfreeOpen(fileName)
 	if err != nil {
-		if os.IsNotExist(err) {
-			log.Printf("Unable to unregister \"%v\" with Parent, err: %v", fileName, err)
-		}
-		return
+		return err
 	}
 	parent := m.findParent(f)
 	if parent == nil {
@@ -71,6 +68,7 @@ func (m *MemMapFs) unRegisterWithParent(fileName string) {
 	pmem := parent.(*mem.File)
 	fmem := f.(*mem.File)
 	mem.RemoveFromMemDir(pmem, fmem)
+	return nil
 }
 
 func (m *MemMapFs) findParent(f File) File {
@@ -136,17 +134,10 @@ func (m *MemMapFs) Mkdir(name string, perm os.FileMode) error {
 	name = normalizePath(name)
 
 	m.mu.RLock()
-	x, ok := m.getData()[name]
+	_, ok := m.getData()[name]
 	m.mu.RUnlock()
 	if ok {
-		// Only return ErrFileExists if it's a file, not a directory.
-		i, err := x.Stat()
-		if !i.IsDir() {
-			return ErrFileExists
-		}
-		if err != nil {
-			return err
-		}
+		return &os.PathError{"mkdir", name, ErrFileExists}
 	} else {
 		m.mu.Lock()
 		item := mem.CreateDir(name)
@@ -158,7 +149,15 @@ func (m *MemMapFs) Mkdir(name string, perm os.FileMode) error {
 }
 
 func (m *MemMapFs) MkdirAll(path string, perm os.FileMode) error {
-	return m.Mkdir(path, perm)
+	err := m.Mkdir(path, perm)
+	if err != nil {
+		if err.(*os.PathError).Err == ErrFileExists {
+			return nil
+		} else {
+			return err
+		}
+	}
+	return nil
 }
 
 // Handle some relative paths
@@ -190,7 +189,7 @@ func (m *MemMapFs) Open(name string) (File, error) {
 	if ok {
 		return f, nil
 	} else {
-		return nil, ErrFileNotFound
+		return nil, &os.PathError{"open", name, ErrFileNotFound}
 	}
 }
 
@@ -200,8 +199,6 @@ func (m *MemMapFs) lockfreeOpen(name string) (File, error) {
 	ff, ok := f.(*mem.File)
 	if ok {
 		ff.Open()
-	}
-	if ok {
 		return f, nil
 	} else {
 		return nil, ErrFileNotFound
@@ -240,7 +237,10 @@ func (m *MemMapFs) Remove(name string) error {
 	defer m.mu.Unlock()
 
 	if _, ok := m.getData()[name]; ok {
-		m.unRegisterWithParent(name)
+		err := m.unRegisterWithParent(name)
+		if err != nil {
+			return &os.PathError{"remove", name, err}
+		}
 		delete(m.getData(), name)
 	} else {
 		return &os.PathError{"remove", name, os.ErrNotExist}
@@ -292,10 +292,10 @@ func (m *MemMapFs) Rename(oldname, newname string) error {
 			m.mu.Unlock()
 			m.mu.RLock()
 		} else {
-			return ErrDestinationExists
+			return &os.PathError{"rename", newname, ErrDestinationExists}
 		}
 	} else {
-		return ErrFileNotFound
+		return &os.PathError{"rename", oldname, ErrFileNotFound}
 	}
 	return nil
 }

memmap_test.go

@@ -1,6 +1,11 @@
 package afero
 
-import "testing"
+import (
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+)
 
 func TestNormalizePath(t *testing.T) {
 	type test struct {
@@ -24,3 +29,74 @@ func TestNormalizePath(t *testing.T) {
 		}
 	}
 }
+
+func TestPathErrors(t *testing.T) {
+	path := filepath.Join(".", "some", "path")
+	path2 := filepath.Join(".", "different", "path")
+	fs := &MemMapFs{}
+	perm := os.FileMode(0755)
+
+	// relevant functions:
+	// func (m *MemMapFs) Chmod(name string, mode os.FileMode) error
+	// func (m *MemMapFs) Chtimes(name string, atime time.Time, mtime time.Time) error
+	// func (m *MemMapFs) Create(name string) (File, error)
+	// func (m *MemMapFs) Mkdir(name string, perm os.FileMode) error
+	// func (m *MemMapFs) MkdirAll(path string, perm os.FileMode) error
+	// func (m *MemMapFs) Open(name string) (File, error)
+	// func (m *MemMapFs) OpenFile(name string, flag int, perm os.FileMode) (File, error)
+	// func (m *MemMapFs) Remove(name string) error
+	// func (m *MemMapFs) Rename(oldname, newname string) error
+	// func (m *MemMapFs) Stat(name string) (os.FileInfo, error)
+
+	err := fs.Chmod(path, perm)
+	checkPathError(t, err, "Chmod")
+
+	err = fs.Chtimes(path, time.Now(), time.Now())
+	checkPathError(t, err, "Chtimes")
+
+	// fs.Create doesn't return an error
+
+	err = fs.Mkdir(path2, perm)
+	if err != nil {
+		t.Error(err)
+	}
+	err = fs.Mkdir(path2, perm)
+	checkPathError(t, err, "Mkdir")
+
+	err = fs.MkdirAll(path2, perm)
+	if err != nil {
+		t.Error("MkdirAll:", err)
+	}
+
+	_, err = fs.Open(path)
+	checkPathError(t, err, "Open")
+
+	_, err = fs.OpenFile(path, os.O_RDWR, perm)
+	checkPathError(t, err, "OpenFile")
+
+	err = fs.Remove(path)
+	checkPathError(t, err, "Remove")
+
+	err = fs.RemoveAll(path)
+	if err != nil {
+		t.Error("RemoveAll:", err)
+	}
+
+	err = fs.Rename(path, path2)
+	checkPathError(t, err, "Rename")
+
+	_, err = fs.Stat(path)
+	checkPathError(t, err, "Stat")
+}
+
+func checkPathError(t *testing.T, err error, op string) {
+	pathErr, ok := err.(*os.PathError)
+	if !ok {
+		t.Error(op+":", err, "is not a os.PathError")
+		return
+	}
+	_, ok = pathErr.Err.(*os.PathError)
+	if ok {
+		t.Error(op+":", err, "contains another os.PathError")
+	}
+}