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What's new in version 2 (part 1/4)

· 5 min read
Loïc Poullain


This article presents some improvements introduced in version 2 of FoalTS:

  • the new CLI commands
  • the service and application initialization
  • the AppController interface
  • custom error-handling & hook post functions
  • accessing file metadata during uploads

This article is the part 1 of the series of articles What's new in version 2.0. Part 2 can be found here.

New CLI commands

In version 1, there were many commands to use, and this, in a specific order. Running and generating migrations from model changes required four commands and building the whole application needed three.

In version 2, the number of CLI commands has been reduced and they have been simplified so that one action matches one command.

Generating migrations

This command generates migrations by comparing the current database schema and the latest changes in your models.

npm run makemigrations

Running migrations

This command builds and runs all migrations.

npm run migrations

Build and run scripts in watch mode (development)

If you want to re-build your scripts each time a file is change, you can execute npm run develop in a separate terminal.

# In one terminal:
npm run develop

# In another terminal:
foal run my-script

Revert one migration

This command reverts the last executed migration.

npm run revertmigration

Build migrations, scripts and the app

This command builds the application, the scripts and the migrations. Unit and e2e tests are not included.

npm run build

Service and Application Initialization

In version 1, it was possible to add an init method to the AppController class and boot methods in the services to initialize the application. These features needed special options in order to be activated.

Starting from version 2, they are enabled by default.

export class AppController {
// ...

init() {
// Execute some code.
export class MyService {
// ...

boot() {
// Execute some code.

The AppController interface

This optional interface allows you to check that the subControllers property has the correct type as well as the init and handleError methods.

export class AppController implements IAppController {
subControllers = [
controller('/api', ApiController)

init() {
// ...

handleError(error, ctx) {
// ...

Custom Error-Handling & Hook Post Functions

In version 1, when an error was thrown or rejected in a hook or a controller method, the remaining hook post functions were not executed.

Starting from version 2, the error is directly converted to an HttpResponseInternalServerError and passed to the next post hook functions.

This can be useful in case we want to use exceptions as HTTP responses without breaking the hook post functions.


class PermissionError extends Error {}

class UserService {

async listUsers(applicant: User): Promise<User[]> {
if (!ctx.user.isAdmin) {
// Use exception here.
throw new PermissionError();

return User.find({ org: });


// This hook measures the execution time and the controller method and hooks.
@Hook(() => {
const time = process.hrtime();

// This post function will still be executed
// even if an error is thrown in listUsers.
return () => {
const seconds = process.hrtime(time)[0];
console.log(`Executed in ${seconds} seconds`);
export class AppController {

users: UserService;

@UseSessions({ user: fetchUser(User) })
listUsers(ctx: Context<User>) {
return new HttpResponseOK(
await users.listUsers(ctx.user)

handleError(error: Error, ctx: Context) {
// Converts the exception to an HTTP response.
// The error can have been thrown in a service used by the controller.
if (error instanceof PermissionError) {
return new HttpResponseForbidden();

// Returns an HttpResponseInternalServerError.
return renderError(error, response);

Accessing File Metadata during Uploads

When using the @ValidateMultipartFormDataBody hook to handle file upload, it is now possible to access the file metadata.


export class UserController {

files: {
profile: { required: true },
uploadProfilePhoto(ctx: Context) {
const file = ctx.request.body.files.profile;
// file.mimeType, file.buffer

Property nameTypeDescription
encodingstringEncoding type of the file
filenamestring\|undefinedName of the file on the user's computer
mimeTypestringMime type of the file
pathstringPath where the file has been saved. If the saveTo option was not provided, the value is an empty string.
bufferBufferBuffer containing the entire file. If the saveTo option was provided, the value is an empty buffer.