Nest: How to use Nest.js & TypeORM with Webpack HMR ?

[Ttou]

I'm submitting a...

[ ] Regression 
[ ] Bug report
[ ] Feature request
[x] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead post your question on Stack Overflow.

Current behavior

if (module['hot']) {
  module['hot'].accept()
  module['hot'].dispose(() => {
    app.close()
  })
}

Expected behavior

Minimal reproduction of the problem with instructions

What is the motivation / use case for changing the behavior?

Environment

Nest version: 5.0.0
TypeORM version: 0.2.5
MySQL version: 2.15.0


For Tooling issues:
- Node version: 8.11.2  
- Platform:  Mac

Others:

[VinceOPS]

Hi.

I think you should post (at least) your connection & configuration code (call to TypeOrmModule.forRoot, for instance).

Btw, if you're loading entities as TS files with a global path (e.g. src/**/*.entity.ts), the default webpack configuration won't allow it / the main script won't run.

[unlight]

There are several issues here:

• When I was creating issue about Ability to reinitialize components of module I hoped for REAL hot swap! But instead we got changed file typescript recompilation, which does not give performance boost at all (with typescript settings transpileOnly: true). Application is still fully reinitialized.
• So you must handle this reinitialization in typeorm and close connection:

import { getConnection } from 'typeorm';

    if (module.hot) {
        const connection = getConnection();
        if (connection.isConnected) {
            await connection.close();
        }
        module.hot.accept();
        module.hot.dispose(() => {
            app.close();
        });
    }

See full example here

• About import entites (same issue with migration), yes glob pattern *.ts will not work, but you can import entites explicitly

import { Cat } from './cat/cat.entity';
import { User } from './user/user.entity';

@Module({
    imports: [
            entities: [
                Cat, User
            ],
        }),
    ],
})

Second option could be webpack require.context feature:

const entityContext = require.context('.', true, /\.entity\.ts$/);
entityContext.keys().forEach(entityContext);

But I did not test it.

Third option is to use ts-node instead of node (which will parse ts files as well) but it's major hit to performance and using webpack hmr aproach does not make sense at all)

[Ttou]

@unlight you can't close connection like that, it will report an error when doing some database operation.

[unlight]

Your errors says "connection is not established", that's why I'm checking flag connection.isConnected.
Anyway it works for me.

[Ttou]

@unlight your code will close the connection at the application startup

[kamilmysliwiec]

I'll extend @nestjs/typeorm with keepConnection (or similar one) option in order to avoid reconnecting between successive compilations.

[kamilmysliwiec]

In latest @nestjs/[email protected] the keepConnectionAlive option is available. Set it to true in order to reuse the same connection between rebuilds. I'll update the docs soon

[lock[bot]]

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