From dc416ce77197d63c6be2e0ce22396b17ffe47cc8 Mon Sep 17 00:00:00 2001
From: FPiety0521 <fpiety0521@gmail.com>
Date: Mon, 14 Oct 2019 03:13:57 -0700
Subject: [PATCH] Only populate db config values if it's not specified

See also: https://github.com/golang-migrate/migrate/issues/262
---
 database/cockroachdb/cockroachdb.go | 20 ++++++++-------
 database/mysql/mysql.go             | 20 ++++++++-------
 database/redshift/redshift.go       | 20 ++++++++-------
 database/sqlserver/sqlserver.go     | 38 ++++++++++++++++-------------
 4 files changed, 54 insertions(+), 44 deletions(-)

diff --git a/database/cockroachdb/cockroachdb.go b/database/cockroachdb/cockroachdb.go
index 8d6c470..ab547e2 100644
--- a/database/cockroachdb/cockroachdb.go
+++ b/database/cockroachdb/cockroachdb.go
@@ -61,17 +61,19 @@ func WithInstance(instance *sql.DB, config *Config) (database.Driver, error) {
 		return nil, err
 	}
 
-	query := `SELECT current_database()`
-	var databaseName string
-	if err := instance.QueryRow(query).Scan(&databaseName); err != nil {
-		return nil, &database.Error{OrigErr: err, Query: []byte(query)}
-	}
+	if config.DatabaseName == "" {
+		query := `SELECT current_database()`
+		var databaseName string
+		if err := instance.QueryRow(query).Scan(&databaseName); err != nil {
+			return nil, &database.Error{OrigErr: err, Query: []byte(query)}
+		}
 
-	if len(databaseName) == 0 {
-		return nil, ErrNoDatabaseName
-	}
+		if len(databaseName) == 0 {
+			return nil, ErrNoDatabaseName
+		}
 
-	config.DatabaseName = databaseName
+		config.DatabaseName = databaseName
+	}
 
 	if len(config.MigrationsTable) == 0 {
 		config.MigrationsTable = DefaultMigrationsTable
diff --git a/database/mysql/mysql.go b/database/mysql/mysql.go
index 27accc3..2c0e0ae 100644
--- a/database/mysql/mysql.go
+++ b/database/mysql/mysql.go
@@ -63,17 +63,19 @@ func WithInstance(instance *sql.DB, config *Config) (database.Driver, error) {
 		return nil, err
 	}
 
-	query := `SELECT DATABASE()`
-	var databaseName sql.NullString
-	if err := instance.QueryRow(query).Scan(&databaseName); err != nil {
-		return nil, &database.Error{OrigErr: err, Query: []byte(query)}
-	}
+	if config.DatabaseName == "" {
+		query := `SELECT DATABASE()`
+		var databaseName sql.NullString
+		if err := instance.QueryRow(query).Scan(&databaseName); err != nil {
+			return nil, &database.Error{OrigErr: err, Query: []byte(query)}
+		}
 
-	if len(databaseName.String) == 0 {
-		return nil, ErrNoDatabaseName
-	}
+		if len(databaseName.String) == 0 {
+			return nil, ErrNoDatabaseName
+		}
 
-	config.DatabaseName = databaseName.String
+		config.DatabaseName = databaseName.String
+	}
 
 	if len(config.MigrationsTable) == 0 {
 		config.MigrationsTable = DefaultMigrationsTable
diff --git a/database/redshift/redshift.go b/database/redshift/redshift.go
index 3d018bd..f8f1644 100644
--- a/database/redshift/redshift.go
+++ b/database/redshift/redshift.go
@@ -53,17 +53,19 @@ func WithInstance(instance *sql.DB, config *Config) (database.Driver, error) {
 		return nil, err
 	}
 
-	query := `SELECT CURRENT_DATABASE()`
-	var databaseName string
-	if err := instance.QueryRow(query).Scan(&databaseName); err != nil {
-		return nil, &database.Error{OrigErr: err, Query: []byte(query)}
-	}
+	if config.DatabaseName == "" {
+		query := `SELECT CURRENT_DATABASE()`
+		var databaseName string
+		if err := instance.QueryRow(query).Scan(&databaseName); err != nil {
+			return nil, &database.Error{OrigErr: err, Query: []byte(query)}
+		}
 
-	if len(databaseName) == 0 {
-		return nil, ErrNoDatabaseName
-	}
+		if len(databaseName) == 0 {
+			return nil, ErrNoDatabaseName
+		}
 
-	config.DatabaseName = databaseName
+		config.DatabaseName = databaseName
+	}
 
 	if len(config.MigrationsTable) == 0 {
 		config.MigrationsTable = DefaultMigrationsTable
diff --git a/database/sqlserver/sqlserver.go b/database/sqlserver/sqlserver.go
index ef99291..3d0514a 100644
--- a/database/sqlserver/sqlserver.go
+++ b/database/sqlserver/sqlserver.go
@@ -65,30 +65,34 @@ func WithInstance(instance *sql.DB, config *Config) (database.Driver, error) {
 		return nil, err
 	}
 
-	query := `SELECT DB_NAME()`
-	var databaseName string
-	if err := instance.QueryRow(query).Scan(&databaseName); err != nil {
-		return nil, &database.Error{OrigErr: err, Query: []byte(query)}
-	}
+	if config.DatabaseName == "" {
+		query := `SELECT DB_NAME()`
+		var databaseName string
+		if err := instance.QueryRow(query).Scan(&databaseName); err != nil {
+			return nil, &database.Error{OrigErr: err, Query: []byte(query)}
+		}
+
+		if len(databaseName) == 0 {
+			return nil, ErrNoDatabaseName
+		}
 
-	if len(databaseName) == 0 {
-		return nil, ErrNoDatabaseName
+		config.DatabaseName = databaseName
 	}
 
-	config.DatabaseName = databaseName
+	if config.SchemaName == "" {
+		query := `SELECT SCHEMA_NAME()`
+		var schemaName string
+		if err := instance.QueryRow(query).Scan(&schemaName); err != nil {
+			return nil, &database.Error{OrigErr: err, Query: []byte(query)}
+		}
 
-	query = `SELECT SCHEMA_NAME()`
-	var schemaName string
-	if err := instance.QueryRow(query).Scan(&schemaName); err != nil {
-		return nil, &database.Error{OrigErr: err, Query: []byte(query)}
-	}
+		if len(schemaName) == 0 {
+			return nil, ErrNoSchema
+		}
 
-	if len(schemaName) == 0 {
-		return nil, ErrNoSchema
+		config.SchemaName = schemaName
 	}
 
-	config.SchemaName = schemaName
-
 	if len(config.MigrationsTable) == 0 {
 		config.MigrationsTable = DefaultMigrationsTable
 	}