tapd: allow migration target version to be specified

This commit allows us to either run all migrations or up to a given
version on the respective stores. This will enable us to test individual
migration steps in unit tests.

Author: guggero

tapdb/migrations.go

@@ -2,6 +2,7 @@ package tapdb
 
 import (
 	"bytes"
+	"errors"
 	"io"
 	"io/fs"
 	"net/http"
@@ -12,11 +13,31 @@ import (
 	"github.com/golang-migrate/migrate/v4/source/httpfs"
 )
 
-// applyMigrations executes all database migration files found in the given file
+// MigrationTarget is a functional option that can be passed to applyMigrations
+// to specify a target version to migrate to.
+type MigrationTarget func(mig *migrate.Migrate) error
+
+var (
+	// TargetLatest is a MigrationTarget that migrates to the latest
+	// version available.
+	TargetLatest = func(mig *migrate.Migrate) error {
+		return mig.Up()
+	}
+
+	// TargetVersion is a MigrationTarget that migrates to the given
+	// version.
+	TargetVersion = func(version uint) MigrationTarget {
+		return func(mig *migrate.Migrate) error {
+			return mig.Migrate(version)
+		}
+	}
+)
+
+// applyMigrations executes database migration files found in the given file
 // system under the given path, using the passed database driver and database
-// name.
-func applyMigrations(fs fs.FS, driver database.Driver, path,
-	dbName string) error {
+// name, up to or down to the given target version.
+func applyMigrations(fs fs.FS, driver database.Driver, path, dbName string,
+	targetVersion MigrationTarget) error {
 
 	// With the migrate instance open, we'll create a new migration source
 	// using the embedded file system stored in sqlSchemas. The library
@@ -36,8 +57,10 @@ func applyMigrations(fs fs.FS, driver database.Driver, path,
 	if err != nil {
 		return err
 	}
-	err = sqlMigrate.Up()
-	if err != nil && err != migrate.ErrNoChange {
+
+	// Execute the migration based on the target given.
+	err = targetVersion(sqlMigrate)
+	if err != nil && !errors.Is(err, migrate.ErrNoChange) {
 		return err
 	}
 

tapdb/postgres.go

@@ -129,7 +129,7 @@ func NewPostgresStore(cfg *PostgresConfig) (*PostgresStore, error) {
 	// Now that the database is open, populate the database with our set of
 	// schemas based on our embedded in-memory file system.
 	if !cfg.SkipMigrations {
-		if err := s.ExecuteMigrations(); err != nil {
+		if err := s.ExecuteMigrations(TargetLatest); err != nil {
 			return nil, fmt.Errorf("error executing migrations: "+
 				"%w", err)
 		}
@@ -138,8 +138,9 @@ func NewPostgresStore(cfg *PostgresConfig) (*PostgresStore, error) {
 	return s, nil
 }
 
-// ExecuteMigrations runs all migrations for the Postgres database.
-func (s *PostgresStore) ExecuteMigrations() error {
+// ExecuteMigrations runs migrations for the Postgres database, depending on the
+// target given, either all migrations or up to a given version.
+func (s *PostgresStore) ExecuteMigrations(target MigrationTarget) error {
 	driver, err := postgres_migrate.WithInstance(
 		s.DB, &postgres_migrate.Config{},
 	)
@@ -149,7 +150,7 @@ func (s *PostgresStore) ExecuteMigrations() error {
 
 	postgresFS := newReplacerFS(sqlSchemas, postgresSchemaReplacements)
 	return applyMigrations(
-		postgresFS, driver, "sqlc/migrations", s.cfg.DBName,
+		postgresFS, driver, "sqlc/migrations", s.cfg.DBName, target,
 	)
 }
 

tapdb/sqlite.go

@@ -140,7 +140,7 @@ func NewSqliteStore(cfg *SqliteConfig) (*SqliteStore, error) {
 	// Now that the database is open, populate the database with our set of
 	// schemas based on our embedded in-memory file system.
 	if !cfg.SkipMigrations {
-		if err := s.ExecuteMigrations(); err != nil {
+		if err := s.ExecuteMigrations(TargetLatest); err != nil {
 			return nil, fmt.Errorf("error executing migrations: "+
 				"%w", err)
 		}
@@ -149,8 +149,9 @@ func NewSqliteStore(cfg *SqliteConfig) (*SqliteStore, error) {
 	return s, nil
 }
 
-// ExecuteMigrations executes all the migrations for the sqlite database.
-func (s *SqliteStore) ExecuteMigrations() error {
+// ExecuteMigrations runs migrations for the sqlite database, depending on the
+// target given, either all migrations or up to a given version.
+func (s *SqliteStore) ExecuteMigrations(target MigrationTarget) error {
 	driver, err := sqlite_migrate.WithInstance(
 		s.DB, &sqlite_migrate.Config{},
 	)
@@ -159,7 +160,9 @@ func (s *SqliteStore) ExecuteMigrations() error {
 	}
 
 	sqliteFS := newReplacerFS(sqlSchemas, sqliteSchemaReplacements)
-	return applyMigrations(sqliteFS, driver, "sqlc/migrations", "sqlite")
+	return applyMigrations(
+		sqliteFS, driver, "sqlc/migrations", "sqlite", target,
+	)
 }
 
 // NewTestSqliteDB is a helper function that creates an SQLite database for