Re: [Quilt-dev] [patch 5/5] Informative message when using graph without graphviz

[Jean Delvare]

Hi Martin,

Le Saturday 18 January 2014 à 01:54 +0100, address@hidden a
écrit :
> pièce jointe document texte brut (graph_depends_on_graphviz)
> Description: Informative message when using graph without graphviz
>  Previously, trying to use the graph subcommand without graphviz being
>  installed resulted in a cryptic error message: 
>  .
>  Can't exec "tred": No such file or directory at 
> /usr/lib/perl/5.14/IO/File.pm line 66, <STDIN> line 1.

As far as I can see, tred is only needed for the --reduce option.
Likewise, dot is needed but only if option -T is passed. If neither
option is passed, quilt graph works without graphviz.

>  graphviz is already in the Suggests field of the debian package, and
>  we cannot raise this dependency severity given the central role of
>  quilt in the debian infrastructure. This informative error message is
>  much more sensible.

I agree that we do not want a hard dependency on graphviz. The graph
subcommand is not a core one, I almost never use it. In openSUSE we did
not even suggest graphviz.

> Author: Martin Quinson <address@hidden>
> Bug-Debian: http://bugs.debian.org/659944
> Forwarded: 2014-01-18
> 
> ---
>  quilt/graph.in |    7 +++++++
>  1 file changed, 7 insertions(+)
> 
> Index: b/quilt/graph.in
> ===================================================================
> --- a/quilt/graph.in
> +++ b/quilt/graph.in
> @@ -17,6 +17,13 @@
>       . $QUILT_DIR/scripts/patchfns
>  fi
>  
> +whichtred=`which /usr/bin/tred`
> +if [ -z "$whichtred" ]

tred doesn't have to be installed in /usr/bin, it could be
in /usr/local/bin or anywhere else. The mail command has a similar "soft
dependency" on formail, and it is handled that way:

# check if formail is installed before doing anything
if ! type formail &> /dev/null
then
        echo $"You have to install 'formail' to use 'quilt mail'" >&2
        exit 1
fi

I believe you should do the same for graphviz. I don't know if some
distributions split graphviz into multiple packages... But just in case,
it would feel safer to check separately for "dot" if option -T is passed
and for "tred" if option --reduce is passed.

> +then
> +     echo $"It seems that graphviz is currently not installed (unable to 
> find the tred binary). You must install it to use 'quilt graph'."
> +     exit 1
> +fi

It would be great to come up with a common error message format that can
be used for all similar cases. Something like:

        printf $"You have to install '%s' (from package '%s') to use 'quilt 
%s'\n" \
               tred graphviz graph >&2

That way we don't have to translate it again and again.

-- 
Jean Delvare
Suse L3 Support