adds a 'status' command that checks for pending migrations.

help.go

@@ -9,6 +9,7 @@ Commands:
   create   - create a new migration in %s with the provided name
   migrate  - run any migrations that haven't been run yet
   rollback - roll back the previous run batch of migrations
+  status   - check if there are pending migrations
   help     - print this help text
 
 Examples:

migrate.go

@@ -23,22 +23,11 @@ func Register(name string, up, down func(orm.DB) error, opts MigrationOptions) {
 }
 
 func migrate(db *pg.DB) (err error) {
-	// sort the registered migrations by name (which will sort by the
-	// timestamp in their names)
-	sort.Slice(migrations, func(i, j int) bool {
-		return migrations[i].Name < migrations[j].Name
-	})
-
-	// look at the migrations table to see the already run migrations
-	completed, err := getCompletedMigrations(db)
+	uncompleted, err := getUncompletedMigrations(db)
 	if err != nil {
 		return err
 	}
 
-	// diff the completed migrations from the registered migrations to find
-	// the migrations we still need to run
-	uncompleted := filterMigrations(migrations, completed, false)
-
 	// if there are no migrations that need to be run, exit early
 	if len(uncompleted) == 0 {
 		fmt.Println("Migrations already up to date")
@@ -91,6 +80,26 @@ func migrate(db *pg.DB) (err error) {
 	return nil
 }
 
+func getUncompletedMigrations(db orm.DB) ([]migration, error) {
+	// sort the registered migrations by name (which will sort by the
+	// timestamp in their names)
+	sort.Slice(migrations, func(i, j int) bool {
+		return migrations[i].Name < migrations[j].Name
+	})
+
+	// look at the migrations table to see the already run migrations
+	completed, err := getCompletedMigrations(db)
+	if err != nil {
+		return nil, err
+	}
+
+	// diff the completed migrations from the registered migrations to find
+	// the migrations we still need to run
+	uncompleted := filterMigrations(migrations, completed, false)
+
+	return uncompleted, nil
+}
+
 func getCompletedMigrations(db orm.DB) ([]migration, error) {
 	var completed []migration
 

migrations.go

@@ -72,6 +72,13 @@ func Run(db *pg.DB, directory string, args []string) error {
 		}
 
 		return rollback(db)
+	case "status":
+		err := ensureMigrationTables(db)
+		if err != nil {
+			return err
+		}
+
+		return migrationStatus(db)
 	default:
 		help(directory)
 		return nil

status.go

@@ -0,0 +1,34 @@
+package migrations
+
+import (
+	"fmt"
+
+	"github.com/go-pg/pg/v10"
+)
+
+func migrationStatus(db *pg.DB) error {
+	uncompleted, err := getUncompletedMigrations(db)
+	if err != nil {
+		return nil
+	}
+
+	if len(uncompleted) == 0 {
+		fmt.Println("Migrations already up to date")
+		return nil
+	}
+
+	return ErrPendingMigrations{len(uncompleted)}
+}
+
+// ErrPendingMigrations is returned by the 'status' command when there is at
+// least one pending migration
+type ErrPendingMigrations struct {
+	N int
+}
+
+func (p ErrPendingMigrations) Error() string {
+	if p.N == 1 {
+		return "1 migration is pending"
+	}
+	return fmt.Sprintf("%d migrations are pending", p.N)
+}

status_test.go

@@ -0,0 +1,58 @@
+package migrations
+
+import (
+	"os"
+	"testing"
+
+	"github.com/go-pg/pg/v10"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMigrationStatus(t *testing.T) {
+	db := pg.Connect(&pg.Options{
+		Addr:     "localhost:5432",
+		User:     os.Getenv("TEST_DATABASE_USER"),
+		Database: os.Getenv("TEST_DATABASE_NAME"),
+	})
+
+	err := ensureMigrationTables(db)
+	require.Nil(t, err)
+
+	defer clearMigrations(t, db)
+	defer resetMigrations(t)
+
+	t.Run("Returns nil if migrations are up to date", func(tt *testing.T) {
+		clearMigrations(tt, db)
+		resetMigrations(tt)
+
+		migrations = []migration{
+			{Name: "123", Up: noopMigration, Down: noopMigration},
+		}
+
+		_, err := db.Model(&migrations[0]).Insert()
+		assert.Nil(tt, err)
+
+		pendingErr := migrationStatus(db)
+		assert.Nil(tt, pendingErr)
+	})
+
+	t.Run("Returns an error if migrations are not up to date", func(tt *testing.T) {
+		clearMigrations(tt, db)
+		resetMigrations(tt)
+
+		migrations = []migration{
+			{Name: "123", Up: noopMigration, Down: noopMigration},
+		}
+
+		pendingErr := migrationStatus(db)
+		assert.EqualError(tt, pendingErr, "1 migration is pending")
+
+		migrations = append(migrations, migration{
+			Name: "123", Up: noopMigration, Down: noopMigration,
+		})
+
+		pendingErr = migrationStatus(db)
+		assert.EqualError(tt, pendingErr, "2 migrations are pending")
+	})
+}