Item7796: TWiki with current Perl: Make CGI::Carp work from TWiki's distribution

In TWiki's scripts, CGI::Carp is required before we have a chance to add TWiki's own lib directories which provide it. This breaks in Perl versions where CGI is no longer part of the Perl core because of incompatible changes in current CPAN versions. See TWiki:Codev.TWikiWithCurrentPerl for details.

• Done in Rev. 30317 (not shown here??) and Rev. 30319. No problems so far, should be good to go. -- TWiki:Main/HaraldJoerg - 2017-05-26

-- TWiki:Main/HaraldJoerg - 2017-04-07

• Needs "more work" to account for Hideyo Imazu's feedback on TWiki:Codev.TWikiWithCurrentPerl - so back to "Being worked on"

-- TWiki:Main.HaraldJoerg - 2017-07-06

Second try.... all files in the bin directory are patched as shown in the attachment nocgi.diff. Now, the procedure is like this:

1. Immediately at start, activate Carp::confess as a die handler. Carp.pm is in Perl core since at least version 5.8.8. This works for CLI and CGI environment, regardless of whether CGI.pm comes with Perl, or is installed on the system, or neither of both.
2. Set $TWiki::cfg{Engine} according to the environment, but do not switch to CGI::Carp for a CGI environment right now.
3. Add the current directory to @INC and require 'setlib.cfg'.
   • Since we've already activated a die handler, problems in setlib.cfg or LocalLib.cfg will provide a stacktrace as confess does (unless suppressed by eval).
4. Now, after setlib.cfg is done, it is safe to switch to CGI::Carp only in a CGI environment and establish CGI::Carp::confess as die handler. At this stage the fallback provided by TWiki's own copy of CGI::Carp is available!

The last step could also be factored out into the equivalent BEGIN block in TWiki.pm.

-- TWiki:Main.HaraldJoerg - 2017-11-02

This seems to be fixed now, marking it ready for release. If needed, open a new item.

-- TWiki:Main.PeterThoeny - 2018-07-15