Fix bug in LevelDB datastore's Delete() method.

LevelDB Delete() method will not return ErrNotFound, so check that the
key exists first by calling Has() and return ds.ErrNotFound if Has()
returns false.

License: MIT
Signed-off-by: Kevin Atkinson <k@kevina.org>

datastore.go

@@ -58,11 +58,17 @@ func (d *datastore) Has(key ds.Key) (exists bool, err error) {
 }
 
 func (d *datastore) Delete(key ds.Key) (err error) {
-	err = d.DB.Delete(key.Bytes(), nil)
-	if err == leveldb.ErrNotFound {
+	// leveldb Delete will not return an error if the key doesn't
+	// exist (see https://github.com/syndtr/goleveldb/issues/109),
+	// so check that the key exists first and if not return an
+	// error
+	exists, err := d.DB.Has(key.Bytes(), nil)
+	if !exists {
 		return ds.ErrNotFound
-	}
+	} else if err != nil {
 		return err
+	}
+	return d.DB.Delete(key.Bytes(), nil)
 }
 
 func (d *datastore) Query(q dsq.Query) (dsq.Results, error) {