Remove Placeholder again (#9)

We only need it for the version argument, and that's safe to use with string concatenation instead.

migrate.go

@@ -11,28 +11,20 @@ import (
 )
 
 var (
-	upMatcher   = regexp.MustCompile(`^([\w]+).up.sql$`)
-	downMatcher = regexp.MustCompile(`^([\w]+).down.sql`)
-)
-
-const (
-	PlaceholderDollar   = "$1"
-	PlaceholderQuestion = "?"
+	upMatcher   = regexp.MustCompile(`^([\w-]+).up.sql$`)
+	downMatcher = regexp.MustCompile(`^([\w-]+).down.sql`)
 )
 
 type Migrator struct {
-	DB          *sql.DB
-	FS          fs.FS
-	Placeholder string
+	DB *sql.DB
+	FS fs.FS
 }
 
 // New Migrator with default options.
-// Migrator.Placeholder default is PlaceholderDollar. You can also use PlaceholderQuestion.
 func New(db *sql.DB, fs fs.FS) *Migrator {
 	return &Migrator{
-		DB:          db,
-		FS:          fs,
-		Placeholder: PlaceholderDollar,
+		DB: db,
+		FS: fs,
 	}
 }
 
@@ -109,7 +101,9 @@ func (m *Migrator) apply(ctx context.Context, name, version string) error {
 		return err
 	}
 	return m.inTransaction(ctx, func(tx *sql.Tx) error {
-		if _, err := tx.ExecContext(ctx, `update migrations set version = `+m.Placeholder, version); err != nil {
+		// Normally we wouldn't just string interpolate the version like this,
+		// but because we know the version has been matched against the regexes, we know it's safe.
+		if _, err := tx.ExecContext(ctx, `update migrations set version = '`+version+`'`); err != nil {
 			return err
 		}
 		if _, err := tx.ExecContext(ctx, string(content)); err != nil {

migrate_test.go

@@ -24,11 +24,10 @@ func TestMigrator(t *testing.T) {
 	tests := []struct {
 		flavor         string
 		createDatabase func(*testing.T) (*sql.DB, func())
-		placeholder    string
 	}{
-		{"postgres", createPostgresDatabase, migrate.PlaceholderDollar},
-		{"maria", createMariaDatabase, migrate.PlaceholderQuestion},
-		{"sqlite", createSQLiteDatabase, migrate.PlaceholderDollar},
+		{"postgres", createPostgresDatabase},
+		{"maria", createMariaDatabase},
+		{"sqlite", createSQLiteDatabase},
 	}
 
 	for _, test := range tests {
@@ -39,7 +38,6 @@ func TestMigrator(t *testing.T) {
 				is := is.New(t)
 
 				m := migrate.New(db, fstest.MapFS{})
-				m.Placeholder = test.placeholder
 
 				err := m.MigrateUp(context.Background())
 				is.NoErr(err)
@@ -56,7 +54,6 @@ func TestMigrator(t *testing.T) {
 				is := is.New(t)
 
 				m := migrate.New(db, mustSub(t, testdata, "testdata/good"))
-				m.Placeholder = test.placeholder
 
 				err := m.MigrateUp(context.Background())
 				is.NoErr(err)
@@ -78,7 +75,6 @@ func TestMigrator(t *testing.T) {
 				is := is.New(t)
 
 				m := migrate.New(db, mustSub(t, testdata, "testdata/good"))
-				m.Placeholder = test.placeholder
 
 				err := m.MigrateUp(context.Background())
 				is.NoErr(err)
@@ -93,7 +89,6 @@ func TestMigrator(t *testing.T) {
 				is := is.New(t)
 
 				m := migrate.New(db, mustSub(t, testdata, "testdata/bad"))
-				m.Placeholder = test.placeholder
 
 				err := m.MigrateUp(context.Background())
 				is.True(err != nil)
@@ -110,7 +105,6 @@ func TestMigrator(t *testing.T) {
 				is := is.New(t)
 
 				m := migrate.New(db, mustSub(t, testdata, "testdata/good"))
-				m.Placeholder = test.placeholder
 
 				err := m.MigrateUp(context.Background())
 				is.NoErr(err)
@@ -134,7 +128,6 @@ func TestMigrator(t *testing.T) {
 				is := is.New(t)
 
 				m := migrate.New(db, mustSub(t, testdata, "testdata/good"))
-				m.Placeholder = test.placeholder
 
 				err := m.MigrateDown(context.Background())
 				is.NoErr(err)