Fix for an empty string as a couchdb key

FAB-12836 #done

Change-Id: I93d55fb4dc07a92a4cd082fb6ecb285381bd8783
Signed-off-by: manish <manish.sethi@gmail.com>

Author: manish-sethi

core/ledger/kvledger/txmgmt/statedb/statecouchdb/couchdoc_conv.go

@@ -216,6 +216,9 @@ func validateKey(key string) error {
 	if strings.HasPrefix(key, "_") {
 		return errors.Errorf("invalid key [%s], cannot begin with \"_\"", key)
 	}
+	if key == "" {
+		return errors.New("invalid key. Empty string is not supported as a key by couchdb")
+	}
 	return nil
 }
 

core/ledger/kvledger/txmgmt/statedb/statecouchdb/statecouchdb_test.go

@@ -160,10 +160,14 @@ func TestUtilityFunctions(t *testing.T) {
 	err = db.ValidateKeyValue("testKey", []byte("Some random bytes"))
 	assert.Nil(t, err)
 
-	// ValidateKey should return an error for an invalid key
+	// ValidateKeyValue should return an error for a key that is not a utf-8 valid string
 	err = db.ValidateKeyValue(string([]byte{0xff, 0xfe, 0xfd}), []byte("Some random bytes"))
 	assert.Error(t, err, "ValidateKey should have thrown an error for an invalid utf-8 string")
 
+	// ValidateKeyValue should return an error for a key that is an empty string
+	assert.EqualError(t, db.ValidateKeyValue("", []byte("validValue")),
+		"invalid key. Empty string is not supported as a key by couchdb")
+
 	reservedFields := []string{"~version", "_id", "_test"}
 
 	// ValidateKeyValue should return an error for a json value that contains one of the reserved fields