Webpack does not recompile non-.d.ts type definitions

[liangchunn]

Webpack does not detect changes made to a pure types file in --watch mode on incremental builds.
I have been struggling with this issue; it's somehow related to #697, but with non-.d.ts files.

// types.ts
export interface AmbientType {
    a: number,
    b: string
}

// index.ts
import { AmbientType } from './types'

const test: AmbientType = {
    a: 2,
    b: ''
}

// tslint:disable-next-line
console.log(test)

After starting webpack in watch mode, removing b: string from types.ts and saving, no errors are emitted.

Expected Behaviour

Webpack recompiles non- .d.ts type definitions

Actual Behaviour

Webpack does not detect changes in types.ts on incremental builds, but fails on a cold build.

Steps to Reproduce the Problem

1. git clone https://github.com/liangchunn/not-recompiling-ts.git
2. cd not-recompiling-ts
3. yarn install
4. yarn start
5. Remove b: string in src/types.ts and save
6. No type errors are reported

Location of a Minimal Repository that Demonstrates the Issue.

https://github.com/liangchunn/not-recompiling-ts

Dependency versions

• webpack@4.12.0
• ts-loader@4.4.1
• typescript@2.9.2

webpack.config.json

https://github.com/liangchunn/typescript-node-scripts/blob/master/lib/webpack.config.dev.js

[liangchunn]

I've found a workaround to this issue by using transpileOnly: true for ts-loader and leveraging fork-ts-checker-webpack-plugin to do the type checking.

Ambient type definitions are still not reloading on save ( issue being tracked here TypeStrong/fork-ts-checker-webpack-plugin#36 ), but it does not 'persist' across incremental builds anymore.

[janwirth]

@liangchunn we have the same issue but pure type definition files are not recompiling - The issue you referenced is exactly about this. Do you have a fix? Would you mind sharing your setup?

[liangchunn]

@FranzSkuffka

AFAIK pure .d.ts files will not recompile automatically; you would need to manually trigger an incremental build by saving a non-.d.ts file.

Here's my configuration for reference: https://github.com/liangchunn/typescript-node-scripts/blob/master/lib/webpack.config.dev.js
(added in this commit liangchunn/typescript-node-scripts@2efac52#diff-937ab2cb5e706721058c9c4712c8208a)

Viel Glück!

[ZSkycat]

I have encountered the same problem. The reason for this problem is not just a pure types file, but a ts file that is not actually used. That is, only type or interface is imported.

This problem can be solved by import './type';

Don't worry. The webpack production mode can removes empty modules and tree shaking. This won't have extra code being packaged. 😄

my case

type.ts

export interface InterfaceA {
    a1: number;
    a2: string;
}

export function test() {
    console.log('test');
}

index.ts

import { InterfaceA } from './type';
// import './type';

export function app(value: InterfaceA) {
    console.log(value.a1.toFixed(0));
    console.log(value.a2.trim());
}

[jlost]

Shouldn't there be a solution to this problem that isn't just a workaround? Is it even possible?