finish implementing mssql db and add tests

.gitignore

@@ -4,4 +4,5 @@ cli/cli
 cli/migrate
 .coverage
 .godoc.pid
-vendor/
+vendor/
+.vscode/

database/mssql/examples/migrations/1085649617_create_users_table.down.sql

@@ -0,0 +1 @@
+DROP TABLE IF EXISTS users;

database/mssql/examples/migrations/1085649617_create_users_table.up.sql

@@ -0,0 +1,5 @@
+CREATE TABLE users (
+  user_id integer unique,
+  name    varchar(40),
+  email   varchar(40)
+);

database/mssql/examples/migrations/1185749658_add_city_to_users.down.sql

@@ -0,0 +1 @@
+ALTER TABLE users DROP COLUMN IF EXISTS city;

database/mssql/examples/migrations/1185749658_add_city_to_users.up.sql

@@ -0,0 +1,3 @@
+ALTER TABLE users ADD city varchar(100);
+
+

database/mssql/examples/migrations/1285849751_add_index_on_user_emails.down.sql

@@ -0,0 +1 @@
+DROP INDEX IF EXISTS users_email_index;

database/mssql/examples/migrations/1285849751_add_index_on_user_emails.up.sql

@@ -0,0 +1,3 @@
+CREATE UNIQUE INDEX users_email_index ON users (email);
+
+-- Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aenean sed interdum velit, tristique iaculis justo. Pellentesque ut porttitor dolor. Donec sit amet pharetra elit. Cras vel ligula ex. Phasellus posuere.

database/mssql/examples/migrations/1385949617_create_books_table.down.sql

@@ -0,0 +1 @@
+DROP TABLE IF EXISTS books;

database/mssql/examples/migrations/1385949617_create_books_table.up.sql

@@ -0,0 +1,5 @@
+CREATE TABLE books (
+  user_id integer,
+  name    varchar(40),
+  author  varchar(40)
+);

database/mssql/examples/migrations/1485949617_create_movies_table.down.sql

@@ -0,0 +1 @@
+DROP TABLE IF EXISTS movies;

database/mssql/examples/migrations/1485949617_create_movies_table.up.sql

@@ -0,0 +1,5 @@
+CREATE TABLE movies (
+  user_id   integer,
+  name      varchar(40),
+  director  varchar(40)
+);

database/mssql/examples/migrations/1585849751_just_a_comment.up.sql

@@ -0,0 +1 @@
+-- Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aenean sed interdum velit, tristique iaculis justo. Pellentesque ut porttitor dolor. Donec sit amet pharetra elit. Cras vel ligula ex. Phasellus posuere.

database/mssql/examples/migrations/1685849751_another_comment.up.sql

@@ -0,0 +1 @@
+-- Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aenean sed interdum velit, tristique iaculis justo. Pellentesque ut porttitor dolor. Donec sit amet pharetra elit. Cras vel ligula ex. Phasellus posuere.

database/mssql/examples/migrations/1785849751_another_comment.up.sql

@@ -0,0 +1 @@
+-- Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aenean sed interdum velit, tristique iaculis justo. Pellentesque ut porttitor dolor. Donec sit amet pharetra elit. Cras vel ligula ex. Phasellus posuere.

database/mssql/examples/migrations/1885849751_another_comment.up.sql

@@ -0,0 +1 @@
+-- Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aenean sed interdum velit, tristique iaculis justo. Pellentesque ut porttitor dolor. Donec sit amet pharetra elit. Cras vel ligula ex. Phasellus posuere.

database/mssql/mssql.go

@@ -8,9 +8,10 @@ import (
 	"io/ioutil"
 	nurl "net/url"
 
-	_ "github.com/denisenkom/go-mssqldb" // mssql support
+	mssql "github.com/denisenkom/go-mssqldb" // mssql support
 	"github.com/golang-migrate/migrate/v4"
 	"github.com/golang-migrate/migrate/v4/database"
+	"github.com/hashicorp/go-multierror"
 )
 
 func init() {
@@ -29,6 +30,13 @@ var (
 	ErrDatabaseDirty  = fmt.Errorf("database is dirty")
 )
 
+var lockErrorMap = map[int]string{
+	-1:   "The lock request timed out.",
+	-2:   "The lock request was canceled.",
+	-3:   "The lock request was chosen as a deadlock victim.",
+	-999: "Parameter validation or other call error.",
+}
+
 // Config for database
 type Config struct {
 	MigrationsTable string
@@ -47,8 +55,7 @@ type MSSQL struct {
 	config *Config
 }
 
-// WithInstance returns a database instance from an already create database connection
-// TODO: WithInstance double check that docs are correct for this function
+// WithInstance returns a database instance from an already created database connection
 func WithInstance(instance *sql.DB, config *Config) (database.Driver, error) {
 	if config == nil {
 		return nil, ErrNilConfig
@@ -105,10 +112,6 @@ func WithInstance(instance *sql.DB, config *Config) (database.Driver, error) {
 	return ss, nil
 }
 
-func dbConnectionString(host, port string) string {
-	return fmt.Sprintf("postgres://postgres@%s:%s/postgres?sslmode=disable", host, port)
-}
-
 // Open a connection to the database
 func (ss *MSSQL) Open(url string) (database.Driver, error) {
 	purl, err := nurl.Parse(url)
@@ -122,14 +125,12 @@ func (ss *MSSQL) Open(url string) (database.Driver, error) {
 	}
 
 	migrationsTable := purl.Query().Get("x-migrations-table")
-	if len(migrationsTable) == 0 {
-		migrationsTable = DefaultMigrationsTable
-	}
 
 	px, err := WithInstance(db, &Config{
 		DatabaseName:    purl.Path,
 		MigrationsTable: migrationsTable,
 	})
+
 	if err != nil {
 		return nil, err
 	}
@@ -158,22 +159,20 @@ func (ss *MSSQL) Lock() error {
 		return err
 	}
 
-	// start a transaction
-	query := "BEGIN TRANSACTION"
-	if _, err := ss.conn.ExecContext(context.Background(), query); err != nil {
-		return &database.Error{OrigErr: err, Err: "get lock transaction", Query: []byte(query)}
-	}
-
 	// This will either obtain the lock immediately and return true,
 	// or return false if the lock cannot be acquired immediately.
 	// MS Docs: sp_getapplock: https://docs.microsoft.com/en-us/sql/relational-databases/system-stored-procedures/sp-getapplock-transact-sql?view=sql-server-2017
-	query = `EXEC sp_getapplock @Resource = ?, @LockMode = 'Update'`
-	if _, err := ss.conn.ExecContext(context.Background(), query, aid); err != nil {
+	query := `EXEC sp_getapplock @Resource = ?, @LockMode = 'Update', @LockOwner = 'Session', @LockTimeout = 0`
+
+	var status mssql.ReturnStatus
+	if _, err = ss.conn.ExecContext(context.Background(), query, aid, &status); err == nil && status > -1 {
+		ss.isLocked = true
+		return nil
+	} else if err != nil {
 		return &database.Error{OrigErr: err, Err: "try lock failed", Query: []byte(query)}
+	} else {
+		return &database.Error{Err: fmt.Sprintf("try lock failed with error %v", lockErrorMap[int(status)]), Query: []byte(query)}
 	}
-
-	ss.isLocked = true
-	return nil
 }
 
 // Unlock froms the migration lock from the database
@@ -188,18 +187,12 @@ func (ss *MSSQL) Unlock() error {
 	}
 
 	// MS Docs: sp_releaseapplock: https://docs.microsoft.com/en-us/sql/relational-databases/system-stored-procedures/sp-releaseapplock-transact-sql?view=sql-server-2017
-	query := `EXEC sp_releaseapplock @Resource = ?`
+	query := `EXEC sp_releaseapplock @Resource = ?, @LockOwner = 'Session'`
 	if _, err := ss.conn.ExecContext(context.Background(), query, aid); err != nil {
 		return &database.Error{OrigErr: err, Query: []byte(query)}
 	}
 	ss.isLocked = false
 
-	// end lock transaction
-	query = "COMMIT"
-	if _, err := ss.conn.ExecContext(context.Background(), query); err != nil {
-		return &database.Error{OrigErr: err, Err: "commit lock transaction", Query: []byte(query)}
-	}
-
 	return nil
 }
 
@@ -213,78 +206,25 @@ func (ss *MSSQL) Run(migration io.Reader) error {
 	// run migration
 	query := string(migr[:])
 	if _, err := ss.conn.ExecContext(context.Background(), query); err != nil {
-		// // FIXME: check for mssql error here
-		// if pgErr, ok := err.(*pq.Error); ok {
-		// 	var line uint
-		// 	var col uint
-		// 	var lineColOK bool
-		// 	if pgErr.Position != "" {
-		// 		if pos, err := strconv.ParseUint(pgErr.Position, 10, 64); err == nil {
-		// 			line, col, lineColOK = computeLineFromPos(query, int(pos))
-		// 		}
-		// 	}
-		// 	message := fmt.Sprintf("migration failed: %s", pgErr.Message)
-		// 	if lineColOK {
-		// 		message = fmt.Sprintf("%s (column %d)", message, col)
-		// 	}
-		// 	if pgErr.Detail != "" {
-		// 		message = fmt.Sprintf("%s, %s", message, pgErr.Detail)
-		// 	}
-		// 	return database.Error{OrigErr: err, Err: message, Query: migr, Line: line}
-		// }
 		return database.Error{OrigErr: err, Err: "migration failed", Query: migr}
 	}
 
 	return nil
 }
 
-// func computeLineFromPos(s string, pos int) (line uint, col uint, ok bool) {
-// 	// replace crlf with lf
-// 	s = strings.Replace(s, "\r\n", "\n", -1)
-// 	// pg docs: pos uses index 1 for the first character, and positions are measured in characters not bytes
-// 	runes := []rune(s)
-// 	if pos > len(runes) {
-// 		return 0, 0, false
-// 	}
-// 	sel := runes[:pos]
-// 	line = uint(runesCount(sel, newLine) + 1)
-// 	col = uint(pos - 1 - runesLastIndex(sel, newLine))
-// 	return line, col, true
-// }
-
-const newLine = '\n'
-
-func runesCount(input []rune, target rune) int {
-	var count int
-	for _, r := range input {
-		if r == target {
-			count++
-		}
-	}
-	return count
-}
-
-func runesLastIndex(input []rune, target rune) int {
-	for i := len(input) - 1; i >= 0; i-- {
-		if input[i] == target {
-			return i
-		}
-	}
-	return -1
-}
-
 // SetVersion for the current database
 func (ss *MSSQL) SetVersion(version int, dirty bool) error {
 
-	tx := ss.db
-	// tx, err := ss.conn.BeginTx(context.Background(), &sql.TxOptions{})
-	// if err != nil {
-	// 	return &database.Error{OrigErr: err, Err: "transaction start failed"}
-	// }
+	tx, err := ss.conn.BeginTx(context.Background(), &sql.TxOptions{})
+	if err != nil {
+		return &database.Error{OrigErr: err, Err: "transaction start failed"}
+	}
 
 	query := `TRUNCATE TABLE "` + ss.config.MigrationsTable + `"`
 	if _, err := tx.Exec(query); err != nil {
-		// tx.Rollback()
+		if errRollback := tx.Rollback(); errRollback != nil {
+			err = multierror.Append(err, errRollback)
+		}
 		return &database.Error{OrigErr: err, Query: []byte(query)}
 	}
 
@@ -295,14 +235,16 @@ func (ss *MSSQL) SetVersion(version int, dirty bool) error {
 		}
 		query = `INSERT INTO "` + ss.config.MigrationsTable + `" (version, dirty) VALUES ($1, $2)`
 		if _, err := tx.Exec(query, version, dirtyBit); err != nil {
-			// tx.Rollback()
+			if errRollback := tx.Rollback(); errRollback != nil {
+				err = multierror.Append(err, errRollback)
+			}
 			return &database.Error{OrigErr: err, Query: []byte(query)}
 		}
 	}
 
-	// if err := tx.Commit(); err != nil {
-	// 	return &database.Error{OrigErr: err, Err: "transaction commit failed"}
-	// }
+	if err := tx.Commit(); err != nil {
+		return &database.Error{OrigErr: err, Err: "transaction commit failed"}
+	}
 
 	return nil
 }
@@ -317,11 +259,6 @@ func (ss *MSSQL) Version() (version int, dirty bool, err error) {
 
 	case err != nil:
 		// FIXME: convert to MSSQL error
-		// if e, ok := err.(*pq.Error); ok {
-		// 	if e.Code.Name() == "undefined_table" {
-		// 		return database.NilVersion, false, nil
-		// 	}
-		// }
 		return 0, false, &database.Error{OrigErr: err, Query: []byte(query)}
 
 	default:
@@ -361,50 +298,24 @@ func (ss *MSSQL) Drop() error {
 		return &database.Error{OrigErr: err, Query: []byte(query)}
 	}
 
-	if err := ss.ensureVersionTable(); err != nil {
-		return err
-	}
-
 	return nil
-
-	// // select all tables in current schema
-	// query := `SELECT t.name FROM sys.tables AS t INNER JOIN sys.schemas AS s ON t.[schema_id] = s.[schema_id] WHERE s.name = N'dbo';`
-	// tables, err := ss.conn.QueryContext(context.Background(), query)
-	// if err != nil {
-	// 	return &database.Error{OrigErr: err, Query: []byte(query)}
-	// }
-	// defer tables.Close()
-
-	// // delete one table after another
-	// tableNames := make([]string, 0)
-	// for tables.Next() {
-	// 	var tableName string
-	// 	if err := tables.Scan(&tableName); err != nil {
-	// 		return err
-	// 	}
-	// 	if len(tableName) > 0 {
-	// 		tableNames = append(tableNames, tableName)
-	// 	}
-	// }
-
-	// if len(tableNames) > 0 {
-	// 	// delete one by one ...
-	// 	for _, t := range tableNames {
-	// 		query = `DROP TABLE IF EXISTS "` + t + `"`
-	// 		if _, err := ss.conn.ExecContext(context.Background(), query); err != nil {
-	// 			return &database.Error{OrigErr: err, Query: []byte(query)}
-	// 		}
-	// 	}
-
-	// 	if err := ss.ensureVersionTable(); err != nil {
-	// 		return err
-	// 	}
-	// }
-
-	// return nil
 }
 
 func (ss *MSSQL) ensureVersionTable() (err error) {
+	if err = ss.Lock(); err != nil {
+		return err
+	}
+
+	defer func() {
+		if e := ss.Unlock(); e != nil {
+			if err == nil {
+				err = e
+			} else {
+				err = multierror.Append(err, e)
+			}
+		}
+	}()
+
 	query := `IF NOT EXISTS
 	(SELECT *
 		 FROM sysobjects