Future Tk version (8.7) may not match Tcl version (9.0)

[chrstphrchvz]

Hello Vadim, I am curious if you happen to know if there is a reason Tcl::Tk initially tries to load Tk with the same version as $tcl_version:

perl-tcl-tk/lib/Tcl/Tk.pm

Lines 576 to 581 in 6e4ff85

	unless ($i->pkg_require('Tk', $i->GetVar('tcl_version'))) {
	warn $@; # in case of failure: warn to show this error for user
	unless ($i->pkg_require('Tk')) { # try w/o version
	die $@; # ...and then re-die to have this error for user
	}
	}

This sort of usage has been present at least since 1.04.

I ask because I predict it will cause a warning for future planned Tcl/Tk releases, where the versions of Tk will not necessarily match the Tcl version. Specifically, there is no Tk 9.0 planned: instead Tk 8.7 will be compatible both with Tcl 8.7 and Tcl 9.0, so it seems there could be a spurious warning for Tcl 9.0 and Tk 8.7.

[vadrer]

I always thought that Tk of some version requires exactly the same tcl version;
if this is not the case - then - of course - that code should be adjusted

[chrstphrchvz]

I have confirmed the warning (from Tcl::pTk) with Tcl 9.0 and Tk 8.7 (and WIP Tcl.pm support from gisle/tcl.pm#42):

can't find package Tk 9.0 at perl-tcl-ptk/blib/lib/Tcl/pTk.pm line 1206.

Tcl::Tk requiring Tk with same version as Tcl appeared in this change long ago: gitpan/Tcl-Tk@233a776#diff-96e9356e1bcff4ae53c4989a768dbba5996b76599be704cf2b691bc5cc6769c1L391-R391. There are plenty of examples in the wild which use/recommend package require Tk $tcl_version or package require Tk [info tclversion], so Tcl::Tk may have been following this rather than merely demonstrating how pkg_require() accepts a version; but I think this practice is likely outdated and unnecessary (one Tcl maintainer said it is a bug for Tk to attempt to load with an incompatible Tcl version: https://groups.google.com/g/comp.lang.tcl/c/pSTxc1RJPBE/m/yXnlVm7WTxkJ). So I will likely propose just using:

$i->pkg_require('Tk') or die $@;

(Though I may prefer at least Carp::croak() or something more helpful than saying just the line number for eval {} with no idea what called it, but I can propose that separately.)