Incremental watch host fixes #1453

[joshcartme]

No description provided.

[Copilot]

Pull Request Overview

This PR fixes issues with the incremental watch host functionality by refactoring how the compiler host is shared across different compilation modes. The changes ensure that the same compiler host instance is used consistently for watch mode, incremental compilation, and regular compilation, preventing potential issues with inconsistent state.

Key changes:

• Moved compiler host creation up to the main compilation function to ensure consistent host usage
• Updated function signatures to accept the host as a parameter instead of creating separate instances
• Added a test case for watch mode with incremental compilation

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
internal/execute/tsc.go	Refactored to create a single compiler host instance and pass it to all compilation functions
internal/execute/watcher.go	Updated createWatcher function to accept compiler host as parameter
internal/execute/tscwatch_test.go	Added test case for watch with tsconfig and incremental compilation
testdata/baselines/reference/tscWatch/commandLineWatch/watch-with-tsconfig-and-incremental.js	New baseline file for the added test case

[jakebailey]

#1457 was supposed to fix the issue; is this PR still needed?

[sheetalkamat]

This is fixed by #1455

[joshcartme]

Oh, yeah #1455 did fix it (I haven't tried it, but it looks about the same)!

My fix is a little different in that instead of creating host in the three functions that can return here,

typescript-go/internal/execute/tsc.go

Lines 189 to 209 in 5ab1364

	if configForCompilation.CompilerOptions().Watch.IsTrue() {
	watcher := createWatcher(sys, configForCompilation, reportDiagnostic, testing)
	watcher.start()
	return CommandLineResult{Status: ExitStatusSuccess, Watcher: watcher}
	} else if configForCompilation.CompilerOptions().IsIncremental() {
	return performIncrementalCompilation(
	sys,
	configForCompilation,
	reportDiagnostic,
	&extendedConfigCache,
	configTime,
	testing,
	)
	}
	return performCompilation(
	sys,
	configForCompilation,
	reportDiagnostic,
	&extendedConfigCache,
	configTime,
	)

it's created before the if/else and then passed in, so it's a little DRYer.

I don't understand the implications of setting ExtendedConfigCacheEntry to nil here:

typescript-go/internal/execute/watcher.go

Line 45 in 5ab1364

w.host = compiler.NewCompilerHost(w.sys.GetCurrentDirectory(), w.sys.FS(), w.sys.DefaultLibraryPath(), nil)

That is different than the other places that create host around there and in this PR I didn't and instead just created host like I saw in the other two places.

Totally happy to close this!

[jakebailey]

nil is okay, just means "make a fresh cache for yourself".

[joshcartme]

Ok got it, closing. Thanks!

[tmm1]

You'll find that --watch still eats a ton of cpu /cc #1317