tsc is very slow in subdirectories of larger project

[bgmort]

Maybe there's something unique to my system or my project going on here, but I'm getting very slow performance from tsc when trying to compile a single file from a subdirectory inside a larger project. The larger project is being compiled with parcel and is not using a .tsconfig file right now. I can demonstrate with a trivial example, see code below.

TypeScript Version:
Version 3.8.0-dev.20200109, 3.7, 3.1 for comparison. All had the same issue.

Search Terms:
tsc, typescript compiler very slow in subdirectories, scanning files outside of root, unused files

Code

~/somepath/lib/sound echo "var s: string = 'hello';"  > hello.ts
~/somepath/lib/sound time tsc hello.ts

real	0m5.592s # <-- very slow
user	0m9.604s
sys	0m0.473s
~/somepath/lib/sound cp hello.ts /tmp/tstmp/
~/somepath/lib/sound pushd /tmp/tstmp/
/tmp/tstmp ls
hello.ts
/tmp/tstmp time tsc hello.ts

real	0m1.916s # <-- less slow
user	0m3.089s
sys	0m0.187s

Expected behavior:
Compiler should not take >5 seconds for a trivial compilation, and should only look at files referenced by the entry file.

Actual behavior:
When compiling a single trivial file (or even trying to compile a file that does not exist) from a subdirectory within a larger project, the compilation took over 5 seconds, vs <2 in a clean directory. But even the 2 seconds for a trivial compilation seems quite slow.

Related Issues:
Lots of issues refer to slow compilation, but I did not find any describing this specific problem.

[RyanCavanaugh]

I would speculate that you have a node_modules/@types folder with a bunch of definitions in them. You can validate by passing --listFiles. By default these are picked up and error-checked; you could also try passing --skipLibCheck which would speed this up substantially.

If that's not it, then we'd need more information to try to help diagnose.

[bgmort]

You are exactly right. This resolves my problem. But it makes me wonder if the default behavior can (or should) be improved. On the other hand, I know that simply running tsc is a relatively uncommon way of building, and would most often happen in a smaller project that doesn't have a large number of external types included. I guess it's probably not something that needs to be addressed.