dialect/sql/schema: allow configuring Atlas to return ErrNoPlan (#3322)

dialect/sql/schema/atlas.go

@@ -33,6 +33,7 @@ type Atlas struct {
 	withFixture bool // deprecated: with fks rename fixture
 	sum         bool // deprecated: sum file generation will be required
 
+	errNoPlan       bool // no plan error enabled
 	universalID     bool // global unique ids
 	dropColumns     bool // drop deleted columns
 	dropIndexes     bool // drop deleted indexes
@@ -183,14 +184,17 @@ func (a *Atlas) NamedDiff(ctx context.Context, name string, tables ...*Table) er
 	default:
 		return fmt.Errorf("unknown migration mode: %q", a.mode)
 	}
-	if err != nil {
+	switch {
+	case err != nil:
 		return err
-	}
-	// Skip if the plan has no changes.
-	if len(plan.Changes) == 0 {
+	case len(plan.Changes) == 0:
+		if a.errNoPlan {
+			return migrate.ErrNoPlan
+		}
 		return nil
+	default:
+		return migrate.NewPlanner(nil, a.dir, opts...).WritePlan(plan)
 	}
-	return migrate.NewPlanner(nil, a.dir, opts...).WritePlan(plan)
 }
 
 func (a *Atlas) cleanSchema(ctx context.Context, name string, err0 error) (err error) {

dialect/sql/schema/migrate.go

@@ -41,6 +41,14 @@ func WithGlobalUniqueID(b bool) MigrateOption {
 	}
 }
 
+// WithErrNoPlan sets Atlas to returns a migrate.ErrNoPlan in case
+// the migration plan is empty. Defaults to false.
+func WithErrNoPlan(b bool) MigrateOption {
+	return func(a *Atlas) {
+		a.errNoPlan = b
+	}
+}
+
 // WithDropColumn sets the columns dropping option to the migration.
 // Defaults to false.
 func WithDropColumn(b bool) MigrateOption {

dialect/sql/schema/migrate_test.go

@@ -305,6 +305,13 @@ func TestMigrate_Diff(t *testing.T) {
 
 	// Checksum will be updated as well.
 	require.NoError(t, migrate.Validate(d))
+
+	require.NoError(t, m.NamedDiff(ctx, "no_changes"), "should not error if WithErrNoPlan is not set")
+	// Enable WithErrNoPlan.
+	m, err = NewMigrate(db, WithFormatter(f), WithDir(d), WithGlobalUniqueID(true), WithErrNoPlan(true))
+	require.NoError(t, err)
+	err = m.NamedDiff(ctx, "no_changes")
+	require.ErrorIs(t, err, migrate.ErrNoPlan)
 }
 
 func requireFileEqual(t *testing.T, name, contents string) {