Add a generic error type to capture non-typed errors

Signed-off-by: Richard Scothern <richard.scothern@gmail.com>

docs/storage/blobserver.go

@@ -36,15 +36,15 @@ func (bs *blobServer) ServeBlob(ctx context.Context, w http.ResponseWriter, r *h
 
 	redirectURL, err := bs.driver.URLFor(ctx, path, map[string]interface{}{"method": r.Method})
 
-	if err == nil {
+	switch err.(type) {
+	case nil:
 		if bs.redirect {
 			// Redirect to storage URL.
 			http.Redirect(w, r, redirectURL, http.StatusTemporaryRedirect)
 			return err
 		}
-	}
 
-	if _, ok := err.(*driver.ErrUnsupportedMethod); ok {
+	case driver.ErrUnsupportedMethod:
 		// Fallback to serving the content directly.
 		br, err := newFileReader(ctx, bs.driver, path, desc.Size)
 		if err != nil {

docs/storage/driver/base/base.go

@@ -52,25 +52,29 @@ type Base struct {
 
 // Format errors received from the storage driver
 func (base *Base) setDriverName(e error) error {
-	if e != nil {
+	switch actual := e.(type) {
-		if actualErr, ok := e.(storagedriver.ErrUnsupportedMethod); ok {
+	case nil:
-			actualErr.DriverName = base.StorageDriver.Name()
+		return nil
-			return actualErr
+	case storagedriver.ErrUnsupportedMethod:
+		actual.DriverName = base.StorageDriver.Name()
+		return actual
+	case storagedriver.PathNotFoundError:
+		actual.DriverName = base.StorageDriver.Name()
+		return actual
+	case storagedriver.InvalidPathError:
+		actual.DriverName = base.StorageDriver.Name()
+		return actual
+	case storagedriver.InvalidOffsetError:
+		actual.DriverName = base.StorageDriver.Name()
+		return actual
+	default:
+		storageError := storagedriver.Error{
+			DriverName: base.StorageDriver.Name(),
+			Enclosed:   e,
 		}
-		if actualErr, ok := e.(storagedriver.PathNotFoundError); ok {
+
-			actualErr.DriverName = base.StorageDriver.Name()
+		return storageError
-			return actualErr
 	}
-		if actualErr, ok := e.(storagedriver.InvalidPathError); ok {
-			actualErr.DriverName = base.StorageDriver.Name()
-			return actualErr
-		}
-		if actualErr, ok := e.(storagedriver.InvalidOffsetError); ok {
-			actualErr.DriverName = base.StorageDriver.Name()
-			return actualErr
-		}
-	}
-	return e
 }
 
 // GetContent wraps GetContent of underlying storage driver.

docs/storage/driver/filesystem/driver.go

@@ -248,7 +248,7 @@ func (d *driver) Delete(ctx context.Context, subPath string) error {
 // URLFor returns a URL which may be used to retrieve the content stored at the given path.
 // May return an UnsupportedMethodErr in certain StorageDriver implementations.
 func (d *driver) URLFor(ctx context.Context, path string, options map[string]interface{}) (string, error) {
-	return "", new(storagedriver.ErrUnsupportedMethod)
+	return "", storagedriver.ErrUnsupportedMethod{}
 }
 
 // fullPath returns the absolute path of a key within the Driver's storage.

docs/storage/driver/gcs/gcs.go

@@ -575,7 +575,7 @@ func (d *driver) Delete(context ctx.Context, path string) error {
 // Returns ErrUnsupportedMethod if this driver has no privateKey
 func (d *driver) URLFor(context ctx.Context, path string, options map[string]interface{}) (string, error) {
 	if d.privateKey == nil {
-		return "", storagedriver.ErrUnsupportedMethod
+		return "", storagedriver.ErrUnsupportedMethod{}
 	}
 
 	name := d.pathToKey(path)
@@ -584,7 +584,7 @@ func (d *driver) URLFor(context ctx.Context, path string, options map[string]int
 	if ok {
 		methodString, ok = method.(string)
 		if !ok || (methodString != "GET" && methodString != "HEAD") {
-			return "", storagedriver.ErrUnsupportedMethod
+			return "", storagedriver.ErrUnsupportedMethod{}
 		}
 	}
 

docs/storage/driver/inmemory/driver.go

@@ -258,5 +258,5 @@ func (d *driver) Delete(ctx context.Context, path string) error {
 // URLFor returns a URL which may be used to retrieve the content stored at the given path.
 // May return an UnsupportedMethodErr in certain StorageDriver implementations.
 func (d *driver) URLFor(ctx context.Context, path string, options map[string]interface{}) (string, error) {
-	return "", new(storagedriver.ErrUnsupportedMethod)
+	return "", storagedriver.ErrUnsupportedMethod{}
 }

docs/storage/driver/oss/oss.go

@@ -748,7 +748,7 @@ func (d *driver) URLFor(ctx context.Context, path string, options map[string]int
 	if ok {
 		methodString, ok = method.(string)
 		if !ok || (methodString != "GET" && methodString != "HEAD") {
-			return "", new(storagedriver.ErrUnsupportedMethod)
+			return "", storagedriver.ErrUnsupportedMethod{}
 		}
 	}
 

docs/storage/driver/rados/rados.go

@@ -496,7 +496,7 @@ func (d *driver) Delete(ctx context.Context, objectPath string) error {
 // URLFor returns a URL which may be used to retrieve the content stored at the given path.
 // May return an UnsupportedMethodErr in certain StorageDriver implementations.
 func (d *driver) URLFor(ctx context.Context, path string, options map[string]interface{}) (string, error) {
-	return "", new(storagedriver.ErrUnsupportedMethod)
+	return "", storagedriver.ErrUnsupportedMethod{}
 }
 
 // Generate a blob identifier

docs/storage/driver/s3/s3.go

@@ -759,7 +759,7 @@ func (d *driver) URLFor(ctx context.Context, path string, options map[string]int
 	if ok {
 		methodString, ok = method.(string)
 		if !ok || (methodString != "GET" && methodString != "HEAD") {
-			return "", new(storagedriver.ErrUnsupportedMethod)
+			return "", storagedriver.ErrUnsupportedMethod{}
 		}
 	}
 

docs/storage/driver/storagedriver.go

@@ -131,3 +131,14 @@ type InvalidOffsetError struct {
 func (err InvalidOffsetError) Error() string {
 	return fmt.Sprintf("[%s] Invalid offset: %d for path: %s", err.DriverName, err.Offset, err.Path)
 }
+
+// Error is a catch-all error type which captures an error string and
+// the driver type on which it occured.
+type Error struct {
+	DriverName string
+	Enclosed   error
+}
+
+func (err Error) Error() string {
+	return fmt.Sprintf("[%s] %s", err.DriverName, err.Enclosed)
+}

docs/storage/driver/testsuites/testsuites.go

@@ -626,7 +626,7 @@ func (suite *DriverSuite) TestURLFor(c *check.C) {
 	c.Assert(err, check.IsNil)
 
 	url, err := suite.StorageDriver.URLFor(suite.ctx, filename, nil)
-	if _, ok := err.(*storagedriver.ErrUnsupportedMethod); ok {
+	if _, ok := err.(storagedriver.ErrUnsupportedMethod); ok {
 		return
 	}
 	c.Assert(err, check.IsNil)
@@ -640,7 +640,7 @@ func (suite *DriverSuite) TestURLFor(c *check.C) {
 	c.Assert(read, check.DeepEquals, contents)
 
 	url, err = suite.StorageDriver.URLFor(suite.ctx, filename, map[string]interface{}{"method": "HEAD"})
-	if _, ok := err.(*storagedriver.ErrUnsupportedMethod); ok {
+	if _, ok := err.(storagedriver.ErrUnsupportedMethod); ok {
 		return
 	}
 	c.Assert(err, check.IsNil)