Re: [PATCH] Makefile: check that tcl/tk is installed

[Christian Couder <christian.couder@gmail.com>]

Hi,

On Mon, Nov 20, 2017 at 8:19 PM, Jonathan Nieder <jrnieder@gmail.com> wrote:
> Hi,
>
> Christian Couder wrote:
>
>> By default running `make install` in the root directory of the
>> project will set TCLTK_PATH to `wish` and then go into the "git-gui"
>> and "gitk-git" sub-directories to build and install these 2
>> sub-projects.
>>
>> When Tcl/Tk is not installed, the above will succeed if gettext
>> is installed, as Tcl/Tk is only required as a substitute for msgfmt
>> when msgfmt is not installed. But then running the installed gitk
>> and git-gui will fail.
>
> Hm, I am not sure I understand the point of this change.  E.g.
> if I run "make install" for git and install tk later, wouldn't I
> want gitk to work?

Yeah, if you know how it all works and want to decide after installing
gitk and git-gui if you actually want to use them, then things are a
bit less straightforward with this patch, though you can still do what
you want by setting the BYPASS_TCLTK_CHECK variable.
But I doubt that many people who are actually building Git are in this case.

> Can you say more about where this comes up?

The original discussion is:

https://public-inbox.org/git/b6b12040-100f-5965-6dfd-344c84dddf96@teddy.ch/

and here are discussions related to version 1 of this patch:

https://public-inbox.org/git/20171115125200.17006-1-chriscool@tuxfamily.org/

As Peff mentions in the original discussion, at the Bloomberg Git
sprint, we saw someone struggling to compile Git, because of these
msgfmt and Tcl/Tk issues.

> gitk is a wrapper
> script
>
>         #!/bin/sh
>         # Tcl ignores the next line -*- tcl -*- \
>         exec wish "$0" -- "$@"
>
> Would some error handling there help?  E.g. something like
>
>         #!/bin/sh
>         # Tcl ignores the next line -*- tcl -*- \
>         exec wish "$0" -- "$@" || \
>         { echo >&2 "Cannot run gitk without tk"; exit 127; }

I think Peff already gave his opinion about this in the above discussions.

>> If neither Tcl/Tk nor gettext are installed, then processing po
>> files will fail in the git-gui directory. The error message when
>> this happens is very confusing to new comers as it is difficult
>> to understand that we tried to use Tcl/Tk as a substitute for
>> msgfmt, and that the solution is to either install gettext or
>> Tcl/Tk, or to set both NO_GETTEXT and NO_TCLTK.
>
> Hm, is this the motivating problem?  This is a condition where
> the rationale for failing the build seems clearer.

This is the issue as well as the above thread that prompted me to take
a look at this.

>> To improve the current behavior when Tcl/Tk is not installed,
>> let's just check that TCLTK_PATH points to something and error
>> out right away if this is not the case.
>
> At first glance I had thought this might set NO_TCLTK automatically,
> which I think would be problematic for the reasons mentioned above.
>
> Erroring out like this patch does and asking the user to explicitly
> confirm that they want to install gitk without Tcl/Tk is less
> problematic,

Yeah that is also my opinion.

> so I am not *against* this patch, just interested in more
> background.

Thanks for taking a look at this,
Christian.