Add comment handling and related tests for migration functionality (#344)

Author: itsfuad

migrate/export_test.go

@@ -3,3 +3,7 @@ package migrate
 func IsCallback(stmt string) (name string) {
 	return isCallback(stmt)
 }
+
+func IsComment(stmt string) bool {
+	return isComment(stmt)
+}

migrate/migrate.go

@@ -201,6 +201,23 @@ func FromFS(ctx context.Context, session gocqlx.Session, f fs.FS) error {
 	return nil
 }
 
+// applyMigration executes a single migration file by parsing and applying its statements.
+// It handles three types of content in migration files:
+//   - SQL statements: executed against the database
+//   - Callback commands: processed via registered callback handlers (format: -- CALL function_name;)
+//   - Regular comments: silently skipped (format: -- any comment text)
+//
+// The function maintains migration state by tracking the number of completed statements,
+// allowing for resumption of partially completed migrations.
+//
+// Parameters:
+//   - ctx: context for cancellation and timeouts
+//   - session: database session for executing statements
+//   - f: filesystem containing the migration file
+//   - path: path to the migration file within the filesystem
+//   - done: number of statements already completed (for resuming partial migrations)
+//
+// Returns an error if the migration fails at any point.
 func applyMigration(ctx context.Context, session gocqlx.Session, f fs.FS, path string, done int) error {
 	file, err := f.Open(path)
 	if err != nil {
@@ -272,19 +289,23 @@ func applyMigration(ctx context.Context, session gocqlx.Session, f fs.FS, path s
 		// trim new lines and all whitespace characters
 		stmt = strings.TrimSpace(stmt)
 
+		// Process statement based on its type
 		if cb := isCallback(stmt); cb != "" {
+			// Handle callback commands (e.g., "-- CALL function_name;")
 			if Callback == nil {
 				return fmt.Errorf("statement %d: missing callback handler while trying to call %s", i, cb)
 			}
 			if err := Callback(ctx, session, CallComment, cb); err != nil {
 				return fmt.Errorf("callback %s: %s", cb, err)
 			}
-		} else {
+		} else if stmt != "" && !isComment(stmt) {
+			// Execute SQL statements (skip empty statements and comments)
 			q := session.ContextQuery(ctx, stmt, nil).RetryPolicy(nil)
 			if err := q.ExecRelease(); err != nil {
 				return fmt.Errorf("statement %d: %s", i, err)
 			}
 		}
+		// Regular comments and empty statements are silently skipped
 
 		// update info
 		info.Done = i
@@ -315,3 +336,10 @@ func isCallback(stmt string) (name string) {
 	}
 	return s[1]
 }
+
+// isComment returns true if the statement is a SQL comment that should be ignored.
+// It distinguishes between regular comments (which should be skipped) and
+// callback commands (which should be processed).
+func isComment(stmt string) bool {
+	return strings.HasPrefix(stmt, "--") && isCallback(stmt) == ""
+}

migrate/migrate_test.go

@@ -160,6 +160,29 @@ func TestMigrationNoSemicolon(t *testing.T) {
 	}
 }
 
+func TestMigrationWithTrailingComment(t *testing.T) {
+	session := gocqlxtest.CreateSession(t)
+	defer session.Close()
+	recreateTables(t, session)
+
+	if err := session.ExecStmt(migrateSchema); err != nil {
+		t.Fatal(err)
+	}
+
+	f := makeTestFS(0)
+	// Create a migration with a trailing comment (this should reproduce the issue)
+	migrationContent := fmt.Sprintf(insertMigrate, 0) + "; -- ttl 1 hour"
+	f.WriteFile("0.cql", []byte(migrationContent), fs.ModePerm)
+
+	ctx := context.Background()
+	if err := migrate.FromFS(ctx, session, f); err != nil {
+		t.Fatal("Migration should succeed with trailing comment, but got error:", err)
+	}
+	if c := countMigrations(t, session); c != 1 {
+		t.Fatal("expected 1 migration got", c)
+	}
+}
+
 func TestIsCallback(t *testing.T) {
 	table := []struct {
 		Name string
@@ -211,6 +234,60 @@ func TestIsCallback(t *testing.T) {
 	}
 }
 
+func TestIsComment(t *testing.T) {
+	table := []struct {
+		Name      string
+		Stmt      string
+		IsComment bool
+	}{
+		{
+			Name:      "CQL statement",
+			Stmt:      "SELECT * from X;",
+			IsComment: false,
+		},
+		{
+			Name:      "Regular comment",
+			Stmt:      "-- This is a comment",
+			IsComment: true,
+		},
+		{
+			Name:      "Comment with additional text",
+			Stmt:      "-- ttl 1 hour",
+			IsComment: true,
+		},
+		{
+			Name:      "Callback command (not a regular comment)",
+			Stmt:      "-- CALL Foo;",
+			IsComment: false,
+		},
+		{
+			Name:      "Callback with spaces (not a regular comment)",
+			Stmt:      "--   CALL Bar;",
+			IsComment: false,
+		},
+		{
+			Name:      "Empty statement",
+			Stmt:      "",
+			IsComment: false,
+		},
+		{
+			Name:      "Whitespace only",
+			Stmt:      "   ",
+			IsComment: false,
+		},
+	}
+
+	for i := range table {
+		test := table[i]
+		t.Run(test.Name, func(t *testing.T) {
+			result := migrate.IsComment(test.Stmt)
+			if result != test.IsComment {
+				t.Errorf("IsComment(%q) = %v, expected %v", test.Stmt, result, test.IsComment)
+			}
+		})
+	}
+}
+
 func TestMigrationCallback(t *testing.T) {
 	var (
 		beforeCalled int