Thanks for pointing this out. I didn't actually know this existed and behaved this way. Sadly I don't think this is quite such a magic bullet as it seems, but it's still a strict benefit and we should do it.

The thing that's missed from the timing data is that tsc --build is only that fast when there's nothing to do. If you run tsc --build repeatedly then it'll take no time at all, whereas running just tsc takes 11s each time. However if you delete the lib directory or change any .ts file then tsc --build and tsc both take the same time.

Generally you're going to run this command when you've changed something, so I don't think this is going to make things faster in the common case, but it is still better in the case where there's nothing to do so we should still make this change.

@RA80533, the CI is complaining that the node modules are out of date, but what it really is I think is that trailing newline in package.json. Can you run npm ci && npm run removeNPMAbsolutePaths to let it format this how it wants. We use this check to make sure the actual node_modules directory is kept up to date, but unfortunately it also sometimes fails on trivial things like this.

Your observation is correct and I should’ve been more specific in my metrics. Builds during development should ultimately end up being much faster, with the ~1,300% increase being the ceiling when no changes have been made. Enabling incremental may also be of additional use but I can’t recall if --build does so implicitly.

I’ll run those commands on the branch when I get home.

It appears that npm ci creates a huge diff. None of the package.json files in node_modules have a final newline. Is this something that should be done separate from this PR?

Did you also run npm run removeNPMAbsolutePaths? If you just run npm ci, then you will see a large diff. The second command will remove all the diffs.

Thanks for sticking with this change!