Adds ability to unwrap ipc errors into their original type

This only works for a specific whitelist of error types, which is
currently all errors in the storagedriver package.

Also improves storagedriver tests to enforce proper error types are
returned

storagedriver/filesystem/driver.go

@@ -84,7 +84,7 @@ func (d *Driver) PutContent(subPath string, contents []byte) error {
 func (d *Driver) ReadStream(path string, offset uint64) (io.ReadCloser, error) {
 	file, err := os.OpenFile(d.subPath(path), os.O_RDONLY, 0644)
 	if err != nil {
-		return nil, err
+		return nil, storagedriver.PathNotFoundError{Path: path}
 	}
 
 	seekPos, err := file.Seek(int64(offset), os.SEEK_SET)
@@ -201,7 +201,14 @@ func (d *Driver) List(subPath string) ([]string, error) {
 // Move moves an object stored at sourcePath to destPath, removing the original
 // object.
 func (d *Driver) Move(sourcePath string, destPath string) error {
-	err := os.Rename(d.subPath(sourcePath), d.subPath(destPath))
+	source := d.subPath(sourcePath)
+	dest := d.subPath(destPath)
+
+	if _, err := os.Stat(source); os.IsNotExist(err) {
+		return storagedriver.PathNotFoundError{Path: sourcePath}
+	}
+
+	err := os.Rename(source, dest)
 	return err
 }
 

storagedriver/ipc/client.go

@@ -126,7 +126,7 @@ func (driver *StorageDriverClient) Start() error {
 	}
 
 	if response.Error != nil {
-		return response.Error
+		return response.Error.Unwrap()
 	}
 
 	driver.version = response.Version
@@ -194,7 +194,7 @@ func (driver *StorageDriverClient) GetContent(path string) ([]byte, error) {
 	}
 
 	if response.Error != nil {
-		return nil, response.Error
+		return nil, response.Error.Unwrap()
 	}
 
 	defer response.Reader.Close()
@@ -226,7 +226,7 @@ func (driver *StorageDriverClient) PutContent(path string, contents []byte) erro
 	}
 
 	if response.Error != nil {
-		return response.Error
+		return response.Error.Unwrap()
 	}
 
 	return nil
@@ -253,7 +253,7 @@ func (driver *StorageDriverClient) ReadStream(path string, offset uint64) (io.Re
 	}
 
 	if response.Error != nil {
-		return nil, response.Error
+		return nil, response.Error.Unwrap()
 	}
 
 	return response.Reader, nil
@@ -280,7 +280,7 @@ func (driver *StorageDriverClient) WriteStream(path string, offset, size uint64,
 	}
 
 	if response.Error != nil {
-		return response.Error
+		return response.Error.Unwrap()
 	}
 
 	return nil
@@ -307,7 +307,7 @@ func (driver *StorageDriverClient) CurrentSize(path string) (uint64, error) {
 	}
 
 	if response.Error != nil {
-		return 0, response.Error
+		return 0, response.Error.Unwrap()
 	}
 
 	return response.Position, nil
@@ -334,7 +334,7 @@ func (driver *StorageDriverClient) List(path string) ([]string, error) {
 	}
 
 	if response.Error != nil {
-		return nil, response.Error
+		return nil, response.Error.Unwrap()
 	}
 
 	return response.Keys, nil
@@ -361,7 +361,7 @@ func (driver *StorageDriverClient) Move(sourcePath string, destPath string) erro
 	}
 
 	if response.Error != nil {
-		return response.Error
+		return response.Error.Unwrap()
 	}
 
 	return nil
@@ -387,7 +387,7 @@ func (driver *StorageDriverClient) Delete(path string) error {
 	}
 
 	if response.Error != nil {
-		return response.Error
+		return response.Error.Unwrap()
 	}
 
 	return nil

storagedriver/ipc/ipc.go

@@ -37,9 +37,13 @@ type Request struct {
 }
 
 // ResponseError is a serializable error type.
+// The Type and Parameters may be used to reconstruct the same error on the
+// client side, falling back to using the Type and Message if this cannot be
+// done.
 type ResponseError struct {
-	Type    string
-	Message string
+	Type       string
+	Message    string
+	Parameters map[string]interface{}
 }
 
 // WrapError wraps an error in a serializable struct containing the error's type
@@ -48,10 +52,52 @@ func WrapError(err error) *ResponseError {
 	if err == nil {
 		return nil
 	}
-	return &ResponseError{
-		Type:    reflect.TypeOf(err).String(),
+	v := reflect.ValueOf(err)
+	re := ResponseError{
+		Type:    v.Type().String(),
 		Message: err.Error(),
 	}
+
+	if v.Kind() == reflect.Struct {
+		re.Parameters = make(map[string]interface{})
+		for i := 0; i < v.NumField(); i++ {
+			field := v.Type().Field(i)
+			re.Parameters[field.Name] = v.Field(i).Interface()
+		}
+	}
+	return &re
+}
+
+// Unwrap returns the underlying error if it can be reconstructed, or the
+// original ResponseError otherwise.
+func (err *ResponseError) Unwrap() error {
+	var errVal reflect.Value
+	var zeroVal reflect.Value
+
+	switch err.Type {
+	case "storagedriver.PathNotFoundError":
+		errVal = reflect.ValueOf(&storagedriver.PathNotFoundError{})
+	case "storagedriver.InvalidOffsetError":
+		errVal = reflect.ValueOf(&storagedriver.InvalidOffsetError{})
+	}
+	if errVal == zeroVal {
+		return err
+	}
+
+	for k, v := range err.Parameters {
+		fieldVal := errVal.Elem().FieldByName(k)
+		if fieldVal == zeroVal {
+			return err
+		}
+		fieldVal.Set(reflect.ValueOf(v))
+	}
+
+	if unwrapped, ok := errVal.Elem().Interface().(error); ok {
+		return unwrapped
+	}
+
+	return err
+
 }
 
 func (err *ResponseError) Error() string {

storagedriver/s3/s3.go

@@ -106,7 +106,11 @@ func New(accessKey string, secretKey string, region aws.Region, encrypt bool, bu
 
 // GetContent retrieves the content stored at "path" as a []byte.
 func (d *Driver) GetContent(path string) ([]byte, error) {
-	return d.Bucket.Get(path)
+	content, err := d.Bucket.Get(path)
+	if err != nil {
+		return nil, storagedriver.PathNotFoundError{Path: path}
+	}
+	return content, nil
 }
 
 // PutContent stores the []byte content at a location designated by "path".
@@ -121,11 +125,10 @@ func (d *Driver) ReadStream(path string, offset uint64) (io.ReadCloser, error) {
 	headers.Add("Range", "bytes="+strconv.FormatUint(offset, 10)+"-")
 
 	resp, err := d.Bucket.GetResponseWithHeaders(path, headers)
-	if resp != nil {
-		return resp.Body, err
+	if err != nil {
+		return nil, storagedriver.PathNotFoundError{Path: path}
 	}
-
-	return nil, err
+	return resp.Body, nil
 }
 
 // WriteStream stores the contents of the provided io.ReadCloser at a location
@@ -242,7 +245,7 @@ func (d *Driver) Move(sourcePath string, destPath string) error {
 		s3.CopyOptions{Options: d.getOptions(), MetadataDirective: "", ContentType: d.getContentType()},
 		d.Bucket.Name+"/"+sourcePath)
 	if err != nil {
-		return err
+		return storagedriver.PathNotFoundError{Path: sourcePath}
 	}
 
 	return d.Delete(sourcePath)

storagedriver/testsuites/testsuites.go

@@ -126,6 +126,7 @@ func (suite *DriverSuite) TestReadNonexistent(c *check.C) {
 	filename := randomString(32)
 	_, err := suite.StorageDriver.GetContent(filename)
 	c.Assert(err, check.NotNil)
+	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
 }
 
 // TestWriteReadStreams1 tests a simple write-read streaming workflow
@@ -247,6 +248,7 @@ func (suite *DriverSuite) TestReadNonexistentStream(c *check.C) {
 	filename := randomString(32)
 	_, err := suite.StorageDriver.ReadStream(filename, 0)
 	c.Assert(err, check.NotNil)
+	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
 }
 
 // TestList checks the returned list of keys after populating a directory tree
@@ -297,6 +299,7 @@ func (suite *DriverSuite) TestMove(c *check.C) {
 
 	_, err = suite.StorageDriver.GetContent(sourcePath)
 	c.Assert(err, check.NotNil)
+	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
 }
 
 // TestMoveNonexistent checks that moving a nonexistent key fails
@@ -306,6 +309,7 @@ func (suite *DriverSuite) TestMoveNonexistent(c *check.C) {
 
 	err := suite.StorageDriver.Move(sourcePath, destPath)
 	c.Assert(err, check.NotNil)
+	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
 }
 
 // TestDelete checks that the delete operation removes data from the storage
@@ -324,6 +328,7 @@ func (suite *DriverSuite) TestDelete(c *check.C) {
 
 	_, err = suite.StorageDriver.GetContent(filename)
 	c.Assert(err, check.NotNil)
+	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
 }
 
 // TestDeleteNonexistent checks that removing a nonexistent key fails
@@ -331,6 +336,7 @@ func (suite *DriverSuite) TestDeleteNonexistent(c *check.C) {
 	filename := randomString(32)
 	err := suite.StorageDriver.Delete(filename)
 	c.Assert(err, check.NotNil)
+	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
 }
 
 // TestDeleteFolder checks that deleting a folder removes all child elements
@@ -354,9 +360,11 @@ func (suite *DriverSuite) TestDeleteFolder(c *check.C) {
 
 	_, err = suite.StorageDriver.GetContent(path.Join(dirname, filename1))
 	c.Assert(err, check.NotNil)
+	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
 
 	_, err = suite.StorageDriver.GetContent(path.Join(dirname, filename2))
 	c.Assert(err, check.NotNil)
+	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
 }
 
 func (suite *DriverSuite) writeReadCompare(c *check.C, filename string, contents, expected []byte) {