`generateTrace` does not work with newer TypeScript versions

[mkantor]

Current behavior

The README describes how to profile slow type-checking by setting generateTrace in tsconfig.json. However this doesn't work with recent TypeScript versions.

Expected behavior

When building with "generateTrace": "./traces" in tsconfig.json, trace files should be created in ./traces as stated in the README.

Steps to reproduce the issue

1. Set up a project with a recent version of TypeScript (I'm using 4.6.2, but I'm nearly certain this problem exists as far back as 4.2.x).
2. Set up a tsconfig.json with "generateTrace": "{folderName}" as described in the README.
3. Do a build.
4. Observe that no trace files were created.

Environment

• fork-ts-checker-webpack-plugin: 6.2.12
• typescript: 4.6.2
• eslint: 7.32.0
• webpack: 4.46.0
• os: macOS 12.0.1

[mkantor]

I think this comes down to relying on internal TypeScript APIs which have changed.

For example:

fork-ts-checker-webpack-plugin/src/typescript/worker/lib/tracing.ts

Line 15 in b5a38c1

const tracing: Tracing | undefined = (typescript as any).tracing;

Since microsoft/TypeScript#42323 it seems that typescript.tracing is undefined until typescript.startTracing is called, but startTracingIfNeeded is written to never call startTracing unless tracing is truthy:

fork-ts-checker-webpack-plugin/src/typescript/worker/lib/tracing.ts

Lines 18 to 24 in b5a38c1

	if (compilerOptions.generateTrace && tracing) {
	tracing.startTracing(
	getConfigFilePathFromCompilerOptions(compilerOptions),
	compilerOptions.generateTrace as string,
	config.build
	);
	}

[mkantor]

Also microsoft/TypeScript#43354 removed getTypeCatalog, but it's relied upon here in stopTracingIfNeeded:

fork-ts-checker-webpack-plugin/src/typescript/worker/lib/tracing.ts

Line 32 in b5a38c1

tracing.stopTracing((program.getProgram() as any).getTypeCatalog());

[mkantor]

Separately, if there was some kind of warning about tracing being skipped even though generateTrace was set it would have helped me understand what was going on much more quickly. Such a warning would be useful for folks using older versions of TypeScript as well (even once this issue is resolved).

[piotr-oles]

@mkantor given that you already know where is the issue and how to solve it, would you mind creating a PR?

[mkantor]

Should generateTrace be supported for various TypeScript versions? I think I know how to address it for TypeScript 4.6.x, but am not sure about past/future releases, and would be worried that a fix which works with my setup might break things for others.

Relatedly, are there any tests that run against different TypeScript versions?

[piotr-oles]

Sorry for the late response. I think it's enough to support it for TypeScript 4.6.x+ - this feature is a minor one.
We have e2e tests that run on different versions of typescript - check the tests/e2e directory. So basically you would have to create a new test that uses generateTrace: './traces' in tsconfig.json, run a webpack build, and check if trace files exist :)

[piotr-oles]

🎉 This issue has been resolved in version 7.2.4 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀