Boot script ordering

[raymondfeng]

The scripts in server/boot are executed by the order of file names as of today.

There are a few use cases that require ordering.

1. A boot script discovers models from a DB and exposes them as REST APIs. It needs to be executed before the api-explorer.
2. An async script that needs to be executed after the system-level boot scripts. For example, if we add the following JS file into server/boot today, the express middleware chain will be messed up:

abc.js (this ensures the file name is sorted before rest-api.js, explorer.js)

module.exports = function(app, cb) {
  process.nextTick(cb);
}

In this case, boot(app, __dirname) returns before the rest-api.js is executed. As a consequence, urlNotFound and errHandler come before the rest handler.

// boot scripts mount components like REST API
boot(app, __dirname);

// -- Mount static files here--
// All static middleware should be registered at the end, as all requests
// passing the static middleware are hitting the file system
// Example:
//   var path = require('path');
//   app.use(loopback.static(path.resolve(__dirname, '../client')));

// Requests that get this far won't be handled
// by any middleware. Convert them into a 404 error
// that will be handled later down the chain.
app.use(loopback.urlNotFound());

// The ultimate error handler.
app.use(loopback.errorHandler());

Potential solutions:

1. Formalize the file names as 01_first.js, 02_second.js for the scaffolded JS files
2. Use phases (preferred)

In addition, we probably should move the urlNotFound/errorHandler middleware code to a boot script too.

[bajtos]

My $0.02:

A boot script discovers models from a DB and exposes them as REST APIs. It needs to be executed before the api-explorer.

This should be fixed in explorer - see strongloop/loopback-component-explorer#22 and strongloop/loopback#686

An async script that needs to be executed after the system-level boot scripts. For example, if we add the following JS file into server/boot today, the express middleware chain will be messed up.

Good point. This is sort of an edge case problem introduced by #50, right?

Potential solutions:
Use phases (preferred)

Yes please.

In addition, we probably should move the urlNotFound/errorHandler middleware code to a boot script too.

Alternatively we can register them with the appropriate middleware phase at the time and place where the middleware phases are defined.

[raymondfeng]

Phase is the magic pain killer 👍

[bajtos]

In October 2018, LoopBack 4.0 GA was released. LoopBack 3 and its supporting modules have entered LTS mode. Per our Long Term Support Policy, this means new features are no longer accepted.

I am closing this GitHub issue as "wont fix".