Scala 3.5.0 runner takes 4X longer to start than scala-cli runner on Windows

[soronpo]

Compiler version

v3.5.0

Minimized code

hello.sc

println("hello")

timeit.bat

@echo off
@setlocal

set start=%time%

:: Runs your command
cmd /c %*

set end=%time%
set options="tokens=1-4 delims=:.,"
for /f %options% %%a in ("%start%") do set start_h=%%a&set /a start_m=100%%b %% 100&set /a start_s=100%%c %% 100&set /a start_ms=100%%d %% 100
for /f %options% %%a in ("%end%") do set end_h=%%a&set /a end_m=100%%b %% 100&set /a end_s=100%%c %% 100&set /a end_ms=100%%d %% 100

set /a hours=%end_h%-%start_h%
set /a mins=%end_m%-%start_m%
set /a secs=%end_s%-%start_s%
set /a ms=%end_ms%-%start_ms%
if %ms% lss 0 set /a secs = %secs% - 1 & set /a ms = 100%ms%
if %secs% lss 0 set /a mins = %mins% - 1 & set /a secs = 60%secs%
if %mins% lss 0 set /a hours = %hours% - 1 & set /a mins = 60%mins%
if %hours% lss 0 set /a hours = 24%hours%
if 1%ms% lss 100 set ms=0%ms%

:: Mission accomplished
set /a totalsecs = %hours%*3600 + %mins%*60 + %secs%
echo command took %hours%:%mins%:%secs%.%ms% (%totalsecs%.%ms%s total)

Output

> timeit scala-cli run hello.sc
hello
command took 0:0:0.64 (0.64s total)

> timeit scala-cli run hello.sc
hello
command took 0:0:0.63 (0.63s total)

> timeit scala-cli run hello.sc
hello
command took 0:0:0.68 (0.68s total)

> timeit scala run hello.sc
hello
command took 0:0:4.57 (4.57s total)

> timeit scala run hello.sc
hello
command took 0:0:4.57 (4.57s total)

> timeit scala run hello.sc
hello
command took 0:0:4.47 (4.47s total)

Expectation

The performance should be roughly the same

[Gedochao]

Hey, so this is a known issue, and has already been fixed.
The fix will be included in 3.5.1 (and is already available in 3.5.1-RC2).

For 3.5.0, on Windows (and only on Windows) the scala script is passing the --cli-version param to work around some other problems, as a result of which we are delegating the runner to a JVM launcher (launched by the windows native launcher).
This is bound to be slow.

We have done that initially to work around some other limitations (namely, support for JVM <17 and the requirement for a Scala CLI launcher to be >=30 days old to be sure it has already been verified by Microsoft), but we have abandoned this solution since then.

This behaviour was removed in #21234 and then backported to 3.5.1-RC2.
You can test this via the coursier installation:

cs install scala:3.5.1-RC2

Closing this issue.