removed duplicated codes and hard-coded switching (#294)

* removed duplicated codes

* remove last hardcoded switch for dialects

connection.go

@@ -53,20 +53,15 @@ func NewConnection(deets *ConnectionDetails) (*Connection, error) {
 	c := &Connection{
 		ID: randx.String(30),
 	}
-	switch deets.Dialect {
-	case "postgres":
-		c.Dialect = newPostgreSQL(deets)
-	case "cockroach":
-		c.Dialect = newCockroach(deets)
-	case "mysql":
-		c.Dialect = newMySQL(deets)
-	case "sqlite3":
-		c.Dialect, err = newSQLite(deets)
+
+	if nc, ok := newConnection[deets.Dialect]; ok {
+		c.Dialect, err = nc(deets)
 		if err != nil {
-			return c, errors.WithStack(err)
+			return c, errors.Wrap(err, "could not create new connection")
 		}
+		return c, nil
 	}
-	return c, nil
+	return nil, errors.Errorf("could not found connection creator for %v", deets.Dialect)
 }
 
 // Connect takes the name of a connection, default is "development", and will
@@ -134,6 +129,17 @@ func (c *Connection) Transaction(fn func(tx *Connection) error) error {
 
 }
 
+// Rollback will open a new transaction and automatically rollback that transaction
+// when the inner function returns, regardless. This can be useful for tests, etc...
+func (c *Connection) Rollback(fn func(tx *Connection)) error {
+	cn, err := c.NewTransaction()
+	if err != nil {
+		return err
+	}
+	fn(cn)
+	return cn.TX.Rollback()
+}
+
 // NewTransaction starts a new transaction on the connection
 func (c *Connection) NewTransaction() (*Connection, error) {
 	var cn *Connection
@@ -163,28 +169,6 @@ func (c *Connection) copy() *Connection {
 	}
 }
 
-// Rollback will open a new transaction and automatically rollback that transaction
-// when the inner function returns, regardless. This can be useful for tests, etc...
-func (c *Connection) Rollback(fn func(tx *Connection)) error {
-	var cn *Connection
-	if c.TX == nil {
-		tx, err := c.Store.Transaction()
-		if err != nil {
-			return errors.Wrap(err, "couldn't start a new transaction")
-		}
-		cn = &Connection{
-			ID:      randx.String(30),
-			Store:   tx,
-			Dialect: c.Dialect,
-			TX:      tx,
-		}
-	} else {
-		cn = c
-	}
-	fn(cn)
-	return cn.TX.Rollback()
-}
-
 // Q creates a new "empty" query for the current connection.
 func (c *Connection) Q() *Query {
 	return Q(c)

dialect_cockroach.go

@@ -26,6 +26,7 @@ func init() {
 	dialectSynonyms["cockroachdb"] = nameCockroach
 	dialectSynonyms["crdb"] = nameCockroach
 	finalizer[nameCockroach] = finalizerCockroach
+	newConnection[nameCockroach] = newCockroach
 }
 
 var _ dialect = &cockroach{}
@@ -271,14 +272,14 @@ func (p *cockroach) TruncateAll(tx *Connection) error {
 	// return tx3.RawQuery(fmt.Sprintf("truncate %s cascade;", strings.Join(tableNames, ", "))).Exec()
 }
 
-func newCockroach(deets *ConnectionDetails) dialect {
+func newCockroach(deets *ConnectionDetails) (dialect, error) {
 	deets.Dialect = "postgres"
 	cd := &cockroach{
 		ConnectionDetails: deets,
 		translateCache:    map[string]string{},
 		mu:                sync.Mutex{},
 	}
-	return cd
+	return cd, nil
 }
 
 func finalizerCockroach(cd *ConnectionDetails) {

dialect_mysql.go

@@ -27,6 +27,7 @@ func init() {
 	AvailableDialects = append(AvailableDialects, nameMySQL)
 	urlParser[nameMySQL] = urlParserMySQL
 	finalizer[nameMySQL] = finalizerMySQL
+	newConnection[nameMySQL] = newMySQL
 }
 
 var _ dialect = &mysql{}
@@ -184,12 +185,11 @@ func (m *mysql) TruncateAll(tx *Connection) error {
 	return tx.RawQuery(qb.String()).Exec()
 }
 
-func newMySQL(deets *ConnectionDetails) dialect {
+func newMySQL(deets *ConnectionDetails) (dialect, error) {
 	cd := &mysql{
 		ConnectionDetails: deets,
 	}
-
-	return cd
+	return cd, nil
 }
 
 func urlParserMySQL(cd *ConnectionDetails) error {

dialect_postgresql.go

@@ -24,6 +24,7 @@ func init() {
 	dialectSynonyms["postgresql"] = namePostgreSQL
 	dialectSynonyms["pg"] = namePostgreSQL
 	finalizer[namePostgreSQL] = finalizerPostgreSQL
+	newConnection[namePostgreSQL] = newPostgreSQL
 }
 
 var _ dialect = &postgresql{}
@@ -198,13 +199,13 @@ func (p *postgresql) TruncateAll(tx *Connection) error {
 	return tx.RawQuery(fmt.Sprintf(pgTruncate, tx.MigrationTableName())).Exec()
 }
 
-func newPostgreSQL(deets *ConnectionDetails) dialect {
+func newPostgreSQL(deets *ConnectionDetails) (dialect, error) {
 	cd := &postgresql{
 		ConnectionDetails: deets,
 		translateCache:    map[string]string{},
 		mu:                sync.Mutex{},
 	}
-	return cd
+	return cd, nil
 }
 
 func finalizerPostgreSQL(cd *ConnectionDetails) {

dialect_sqlite.go

@@ -28,6 +28,7 @@ func init() {
 	AvailableDialects = append(AvailableDialects, nameSQLite3)
 	dialectSynonyms["sqlite"] = nameSQLite3
 	urlParser[nameSQLite3] = urlParserSQLite3
+	newConnection[nameSQLite3] = newSQLite
 }
 
 var _ dialect = &sqlite{}

dialect_sqlite_shim.go

@@ -6,6 +6,14 @@ import (
 	"errors"
 )
 
+const nameSQLite3 = "sqlite3"
+
+func init() {
+	AvailableDialects = append(AvailableDialects, nameSQLite3)
+	dialectSynonyms["sqlite"] = nameSQLite3
+	newConnection[nameSQLite3] = newSQLite
+}
+
 func newSQLite(deets *ConnectionDetails) (dialect, error) {
 	return nil, errors.New("sqlite3 support was not compiled into the binary")
 }

pop.go

@@ -13,6 +13,9 @@ var urlParser = make(map[string]func(*ConnectionDetails) error)
 // map of dialect specific connection details finalizers
 var finalizer = make(map[string]func(*ConnectionDetails))
 
+// map of connection creators
+var newConnection = make(map[string]func(*ConnectionDetails) (dialect, error))
+
 // DialectSupported checks support for the given database dialect
 func DialectSupported(d string) bool {
 	for _, ad := range AvailableDialects {