Slow Performance on Incremental Runs (Project References)

[nathanforce]

Current behavior

Incremental typechecks are very slow.

We have a project that leverages Project References in Typescript. As the latest release of your plugin supports references we tried to upgrade. We are seeing an unusable drop in performance when type-checking this code.

For comparison, here is the same code change ran with tsc --build --incremental

Here is our config:

      new ForkTsCheckerWebpackPlugin({
        async: true,
        typescript: {
          mode: 'write-references',
          configFile: path.resolve(APP_ROOT, 'tsconfig.json'),
          configOverwrite: {
            compilerOptions: {
              incremental: true
            }
          },
          profile: true,
          build: true
        }
      }),

Expected behavior

Incremental typechecks should be quick.

Environment

• fork-ts-checker-webpack-plugin: 5.0.0
• typescript: 3.7.2
• eslint: n/a
• webpack: 4.39.3
• os: macos

[piotr-oles]

Hi,
Thanks for reporting this issue. Could you check timings using tsc --build --incremental --watch? This is the API we use and the performance drop is not in the initial compilation but in the next one.

[nathanforce]

Sure thing. I've attached the comparison.

tsc --build --incremental --watch

Webpack, showing both initial compilation and then after a file change.

One interesting thing I see is that tsc reports 1318 files while webpack reports 2111 modules. Not sure if that mismatch indicates anything.

[piotr-oles]

Is there any chance of getting a reproduction repository?

[nathanforce]

https://github.com/nathanforce/monorepo-ts-projects-webpack

@piotr-oles Here's my best attempt. It is very simplistic but follows the same structure/patterns as the real repo, just with far less files. Even in this tiny example I am seeing slower numbers on the webpack side when running the two commands:

webpack:

npx webpack-dev-server --mode=development --config ./apps/alpha/webpack.config.js

tsc:

npx tsc --build ./apps/alpha/tsconfig.json --extendedDiagnostics --incremental --watch

As is expected in such a contrived reproduction, the differences here are much much smaller but maybe it can help you spot something. Sorry for the delay!

Cheers

[piotr-oles]

I will try to take a look at this in a few days :)

[nathanforce]

@piotr-oles #494 seems to have helped a bit but the typecheck times using Webpack/plugin are still much higher than using tsc. Below screenshot shows the two running side by side for the same change.

tsc:

[piotr-oles]

Cool that there is a progress - I will profile it again :)

[quicksnap]

Thanks for looking into this. I just upgraded to this version on a branch and I believe we're experiencing the same problems.