`async` setting is not respected for tapAfterCompileToAddDependencies

[markjm]

Current behavior

When async is set to true, issues will be surfaced asynchronously via tapDoneToAsyncGetIssues. However, the first recompilation gets blocked in tapAfterCompileToAddDependencies due to the webpack compilation waiting on state.dependencies promise. When TS compilation is very slow or broken (as there seemed to be in 4.3.2 for us), this causes webpack compilation to hang with no indication of what is going wrong.

Expected behavior

When async is set, triggering a recompilation via file save should happen immediately, instead of being stuck behind initial TS project compilation to add dependencies.

Steps to reproduce the issue

It is tough to create a clear repro because this only happens when repo is so big or having issues that this step takes a long time. To emulate it, you can set state.dependenciesPromise to just be a very long sleep promise and see that recompilations after the first can not start until that is complete.

Proposed fix

I have attached a proposed fix patch that is working for us. I worry I may be missing some potential leak by not waiting for this promise, but it has been working will in our large repo for about a week now

diff --git a/node_modules/fork-ts-checker-webpack-plugin/lib/hooks/tapAfterCompileToAddDependencies.js b/node_modules/fork-ts-checker-webpack-plugin/lib/hooks/tapAfterCompileToAddDependencies.js
index f5155a2..589846a 100644
--- a/node_modules/fork-ts-checker-webpack-plugin/lib/hooks/tapAfterCompileToAddDependencies.js
+++ b/node_modules/fork-ts-checker-webpack-plugin/lib/hooks/tapAfterCompileToAddDependencies.js
@@ -10,7 +10,11 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
 };
 Object.defineProperty(exports, "__esModule", { value: true });
 function tapAfterCompileToAddDependencies(compiler, configuration, state) {
-    compiler.hooks.afterCompile.tapPromise('ForkTsCheckerWebpackPlugin', (compilation) => __awaiter(this, void 0, void 0, function* () {
+    const tapFn = configuration.async
+        ? compiler.hooks.afterCompile.tap
+        : compiler.hooks.afterCompile.tapPromise;
+        
+    tapFn.call(compiler.hooks.afterCompile, 'ForkTsCheckerWebpackPlugin', (compilation) => __awaiter(this, void 0, void 0, function* () {
         if (compilation.compiler !== compiler) {
             // run only for the compiler that the plugin was registered for
             return;

Environment

• fork-ts-checker-webpack-plugin: 6.2.13
• typescript: 4.3.2
• eslint: NA
• webpack: 5.46.0
• os: Windows

[piotr-oles]

I can't add it to async, because it will create some race conditions in how webpack watches files. This will also potentially break our E2E tests :/
I'm working on a new release of the plugin which will have a separate thread for dependencies and separate for diagnostics. It will still be sync for dependencies, but computing dependencies on its own should be fast enough (it only parses tsconfig.json file(s)). Currently it can be blocked by diagnostics checks because it runs on the same thread and typescript diagnostics are synchronous.

[piotr-oles]

There should be a new version released in a few minutes. It should fix this issue :) Could you confirm?

[markjm]

Let me try it later this week. Thanks!