In TypeScript 2.8 a regression was introduced where compilation in watch mode under linux went from ~5 seconds on initial compilation to about ~32 seconds (or more, depending on the number of files/folders being watched). I've seen some projects taking nearly 2 minutes to do initial watch compilation under > 2.8.
I've executed the watch commands under 2.7 and under 2.9 for comparision and generated v8 profiles for both of them.
The problem from what I understood is somehow related to 2.9 scanning every single folder and file from the project root down even if it's not included or excluded. Through debugging I've seen it recursively scan to the depths of .git or node_modules, which was a behaviour it did not had in 2.7, which is consistent with what I have observed of the initial compilation time being slower and slower as the dependencies grow.
TypeScript Issue #25018
Just npm install && docker-compose up. You can change the command that
is executed inside docker by modifying docker-command.sh
See typescript-272-prof-process.txt for profilling details
node_modules/.bin/tsc --watch --extendedDiagnostics
08:31:33 - Starting compilation in watch mode...
Files: 61
Lines: 62744
Nodes: 273576
Identifiers: 98075
Symbols: 80280
Types: 29130
Memory used: 125488K
I/O Read time: 0.19s
Parse time: 0.77s
Program time: 1.97s
Bind time: 0.48s
Check time: 1.62s
transformTime time: 0.02s
printTime time: 0.02s
Emit time: 0.04s
commentTime time: 0.00s
Source Map time: 0.00s
I/O Write time: 0.01s
Total time: 4.12s <<<<<<<<< see
08:31:37 - Compilation complete. Watching for file changes.
See typescript-292-prof-process.txt for profiling details
node_modules/.bin/tsc --watch --extendedDiagnostics
08:27:10 - Starting compilation in watch mode..
[redacted]
08:27:43 - Found 0 errors. Watching for file changes.
Files: 61
Lines: 63371
Nodes: 279942
Identifiers: 99371
Symbols: 79865
Types: 30108
Memory used: 140212K
I/O Read time: 0.18s
Parse time: 0.70s
Program time: 30.17s
Bind time: 0.45s
Check time: 1.80s
transformTime time: 0.02s
commentTime time: 0.00s
Source Map time: 0.00s
I/O Write time: 0.01s
printTime time: 0.05s
Emit time: 0.05s
Total time: 32.47s <<<<<<<<< see
See typescript-300dev-prof-process.txt for profiling details
21:15:10 - Starting compilation in watch mode...
21:15:42 - Found 0 errors. Watching for file changes.
Files: 67
Lines: 64772
Nodes: 284175
Identifiers: 100872
Symbols: 81598
Types: 30924
Memory used: 147366K
I/O Read time: 0.19s
Parse time: 0.74s
Program time: 29.77s
Bind time: 0.48s
Check time: 1.77s
transformTime time: 0.03s
commentTime time: 0.00s
Source Map time: 0.00s
I/O Write time: 0.01s
printTime time: 0.07s
Emit time: 0.07s
Total time: 32.09s