Loopback 4 example - convert lamdba-wrapper.js to Typescript equivalent.

[awongCM]

Hi, I've followed the loopback 4 example for this and I really like how you have the framework to play nicely with serverless framework when following the tutorial!

The thing I'm confused about is the lambda wrapper js file.

https://github.com/botbits/serverless-loopback/blob/master/examples/lb4-express/src/lambda-wrapper.js

Could it not have been better to rewrite it in Typescript in the following:

import {ExpressServer} from '../server';

import serverless from 'serverless-http';

import {ApplicationConfig} from '@loopback/core';

let app: Function;

async function main(options: ApplicationConfig) {
  const server = new ExpressServer(options);
  app = serverless(server.app);
  await server.boot();
  await server.start();
  console.log('Server is running at http://127.0.0.1:3000');
}

exports.handler = async function handler(
  request: Object,
  ...context: Object[]
) {
  if (app === undefined) {
    // Run the application
    const config = {
      rest: {
        port: +(process.env.PORT ? process.env.PORT : 3000),
        host: process.env.HOST ? process.env.HOST : 'localhost',
        openApiSpec: {
          // useful when used with OpenAPI-to-GraphQL to locate your application
          setServersFromRequest: true,
        },
        // Use the LB4 application as a route. It should not be listening.
        listenOnStart: false,
      },
    };
    await main(config).catch(err => {
      console.error('Cannot start the application.', err);
      process.exit(1);
    });
  }
  return app(request, ...context);
};

That way, you don't need to configure tsconfig.json to include raw JS files as part of the build process and you only have Typescript files to work with, not JS/Typescript files combo..

I'm just curious what's your rationale is keeping both JS and Typescript this way.

[marcelobern]

Hi @awongCM, happy to hear you found the tutorial useful!

To the best of my recollection, the reason for JS rather than TS was that LB4 was added as a fix and I did not spend the time to look into the TS code as I was unfamiliar with TypeScript :-)

If you feel comfortable, please go ahead and create a PR for this change.

Or if you prefer, I can do the PR with the code provided.

[awongCM]

Hi @awongCM, happy to hear you found the tutorial useful!

To the best of my recollection, the reason for JS rather than TS was that LB4 was added as a fix and I did not spend the time to look into the TS code as I was unfamiliar with TypeScript :-)

If you feel comfortable, please go ahead and create a PR for this change.

Or if you prefer, I can do the PR with the code provided.

Hi @marcelobern

Ah. That makes sense!

Thank you for the candid reply. I certainly enjoy the tutorial - without a doubt! I have been working on my own pet serverless projects on my profile, and I've been recommended by my colleague how great the loopback framework is for building enterprise-level microservices due to its strong DDD philosophy.

Thus it had me pondering how to incorporate loopback's microservices architecture into the serverless world until I googled "loopback serverless" which lead me to your GitHub repo as the first search result page.. ;)

I'm more than happy to contribute. 👍

Let me create one and get back to on the PR submitted.

[awongCM]

@marcelobern

I create my local PR; did the above code to replace .js counterpart file.

But when I tried to run presls-deploy, I ran into the following:

node_modules/@loopback/testlab/node_modules/@types/express-serve-static-core/index.d.ts:1183:31 - error TS1005: ';' expected.

1183      * Render the given view `name` name with `options`
                                   ~~~~

node_modules/@loopback/testlab/node_modules/@types/express-serve-static-core/index.d.ts:1183:48 - error TS1005: ';' expected.

1183      * Render the given view `name` name with `options`
                                                    ~~~~~~~

node_modules/@loopback/testlab/node_modules/@types/express-serve-static-core/index.d.ts:1199:16 - error TS1005: ';' expected.

1199      * A node `http.Server` is returned, with this
                    ~~~~

node_modules/@loopback/testlab/node_modules/@types/express-serve-static-core/index.d.ts:1200:33 - error TS1005: ';' expected.

1200      * application (which is a `Function`) as its
                                     ~~~~~~~~

node_modules/@loopback/testlab/node_modules/@types/express-serve-static-core/index.d.ts:1268:1 - error TS1160: Unterminated template literal.

1268 
     

I'm getting lot of Typescript compilation errors... 😕

[marcelobern]

@awongCM this brings some memories.

I vaguely recall getting into some TypeScript issues that I did not know how to solve and wanted to add the lb4 sample.

So I guess these might have been it :-D

I am not sure I can help you with the TypeScript errors, but I will ask you all the same. How can I help?

[awongCM]

@awongCM this brings some memories.

I vaguely recall getting into some TypeScript issues that I did not know how to solve and wanted to add the lb4 sample.

So I guess these might have been it :-D

I am not sure I can help you with the TypeScript errors, but I will ask you all the same. How can I help?

Interesting.

Odd thing is that I never run into any problems when cloning the loopback4 examples as a separate project; followed the tutorial; convert the main lambda wrapper to Typescript.

It works fine there after.

Perhaps there's some config settings from either tsconfig.json or similar that's not liking here...