fix: Fix nested transactions should function correctly (#2470)

* fix: Fix nested transactions should function correctly

Inner tx should reuse outer tx

coderd/database/db.go

@@ -47,9 +47,17 @@ type sqlQuerier struct {
 
 // InTx performs database operations inside a transaction.
 func (q *sqlQuerier) InTx(function func(Store) error) error {
-	if q.sdb == nil {
+	if _, ok := q.db.(*sql.Tx); ok {
+		// If the current inner "db" is already a transaction, we just reuse it.
+		// We do not need to handle commit/rollback as the outer tx will handle
+		// that.
+		err := function(q)
+		if err != nil {
+			return xerrors.Errorf("execute transaction: %w", err)
+		}
 		return nil
 	}
+
 	transaction, err := q.sdb.Begin()
 	if err != nil {
 		return xerrors.Errorf("begin transaction: %w", err)

coderd/database/db_test.go

@@ -0,0 +1,46 @@
+//go:build linux
+
+package database_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/require"
+
+	"github.com/coder/coder/coderd/database"
+)
+
+func TestNestedInTx(t *testing.T) {
+	t.Parallel()
+
+	uid := uuid.New()
+	sqlDB := testSQLDB(t)
+	err := database.MigrateUp(sqlDB)
+	require.NoError(t, err, "migrations")
+
+	db := database.New(sqlDB)
+	err = db.InTx(func(outer database.Store) error {
+		return outer.InTx(func(inner database.Store) error {
+			//nolint:gocritic
+			require.Equal(t, outer, inner, "should be same transaction")
+
+			_, err := inner.InsertUser(context.Background(), database.InsertUserParams{
+				ID:             uid,
+				Email:          "coder@coder.com",
+				Username:       "coder",
+				HashedPassword: []byte{},
+				CreatedAt:      database.Now(),
+				UpdatedAt:      database.Now(),
+				RBACRoles:      []string{},
+			})
+			return err
+		})
+	})
+	require.NoError(t, err, "outer tx: %w", err)
+
+	user, err := db.GetUserByID(context.Background(), uid)
+	require.NoError(t, err, "user exists")
+	require.Equal(t, uid, user.ID, "user id expected")
+}