fix: Improve provider apply() errors (#660)

provider.go

@@ -409,8 +409,16 @@ func (p *Provider) apply(
 	if err != nil && !errors.Is(err, database.ErrVersionNotFound) {
 		return nil, err
 	}
-	// If the migration has already been applied, return an error. But, if the migration is being
-	// rolled back, we allow the individual migration to be applied again.
+	// There are a few states here:
+	//  1. direction is up
+	//    a. migration is applied, this is an error (ErrAlreadyApplied)
+	//    b. migration is not applied, apply it
+	//  2. direction is down
+	//    a. migration is applied, rollback
+	//    b. migration is not applied, this is an error (ErrNotApplied)
+	if result == nil && !direction {
+		return nil, fmt.Errorf("version %d: %w", version, ErrNotApplied)
+	}
 	if result != nil && direction {
 		return nil, fmt.Errorf("version %d: %w", version, ErrAlreadyApplied)
 	}

provider_errors.go

@@ -6,15 +6,21 @@ import (
 )
 
 var (
-	// ErrVersionNotFound when a migration version is not found.
+	// ErrVersionNotFound is returned when a specific migration version is not located. This can
+	// occur if a .sql file or a Go migration function for the specified version is missing.
 	ErrVersionNotFound = errors.New("version not found")
 
-	// ErrAlreadyApplied when a migration has already been applied.
-	ErrAlreadyApplied = errors.New("already applied")
-
 	// ErrNoMigrations is returned by [NewProvider] when no migrations are found.
 	ErrNoMigrations = errors.New("no migrations found")
 
+	// ErrAlreadyApplied indicates that the migration cannot be applied because it has already been
+	// executed. This error is returned by [Provider.Apply].
+	ErrAlreadyApplied = errors.New("migration already applied")
+
+	// ErrNotApplied indicates that the rollback cannot be performed because the migration has not
+	// yet been applied. This error is returned by [Provider.Apply].
+	ErrNotApplied = errors.New("migration not applied")
+
 	// errInvalidVersion is returned when a migration version is invalid.
 	errInvalidVersion = errors.New("version must be greater than 0")
 )

provider_run_test.go

@@ -262,7 +262,7 @@ func TestProviderRun(t *testing.T) {
 		_, err = p.ApplyVersion(ctx, 1, true)
 		check.HasError(t, err)
 		check.Bool(t, errors.Is(err, goose.ErrAlreadyApplied), true)
-		check.Contains(t, err.Error(), "version 1: already applied")
+		check.Contains(t, err.Error(), "version 1: migration already applied")
 	})
 	t.Run("status", func(t *testing.T) {
 		ctx := context.Background()
@@ -765,6 +765,20 @@ func TestCustomStoreTableExists(t *testing.T) {
 	check.NoError(t, err)
 }
 
+func TestProviderApply(t *testing.T) {
+	t.Parallel()
+
+	ctx := context.Background()
+	p, err := goose.NewProvider(goose.DialectSQLite3, newDB(t), newFsys())
+	check.NoError(t, err)
+	_, err = p.ApplyVersion(ctx, 1, true)
+	check.NoError(t, err)
+	// This version has a corresponding down migration, but has never been applied.
+	_, err = p.ApplyVersion(ctx, 2, false)
+	check.HasError(t, err)
+	check.Bool(t, errors.Is(err, goose.ErrNotApplied), true)
+}
+
 type customStoreSQLite3 struct {
 	database.Store
 }

provider_types.go

@@ -1,6 +1,10 @@
 package goose
 
-import "time"
+import (
+	"fmt"
+	"path/filepath"
+	"time"
+)
 
 // MigrationType is the type of migration.
 type MigrationType string
@@ -32,6 +36,19 @@ type MigrationResult struct {
 	Error error
 }
 
+func (m *MigrationResult) String() string {
+	state := "OK"
+	if m.Empty {
+		state = "EMPTY"
+	}
+	return fmt.Sprintf("%-6s %-4s %s (%s)",
+		state,
+		m.Direction,
+		filepath.Base(m.Source.Path),
+		truncateDuration(m.Duration),
+	)
+}
+
 // State represents the state of a migration.
 type State string