Feature Proposal: Enable TML authors to see the topics that comprise the preference stack

Motivation

The Preferences stack is a confusing concept, and it is helpful to be able to explicitly see the actual topics.

Description and Documentation

Examples

Impact

WhatDoesItAffect:

%WHATDOESITAFFECT%

edit

Implementation

Foswiki.pm
        VARIABLESTACK => sub { $_[0]->{prefs}->stringifyTopicNames() },

Prefs.pm
sub stringifyTopicNames {
    my ( $this, $key ) = @_;
    my $stack = $this->{main};
    my @r = $stack->getTopicNames();
    return join ',', @r;
}

Stack.pm
sub getTopicNames {
    my $this = shift;
    my @ret;
    foreach my $back ( @{ $this->{'levels'} } ) {
        my $path = "ANON";
        
        if ($back->can('topicObject')) {
            my $obj = $back->topicObject();
            $path = $obj->getPath();
        }
        push @ret, $path;
    }
    return @ret;
}

-- Contributors: KipLubliner - 23 Oct 2012

Discussion

I very much support this.

I've had the idea at a high level to build in 'explain' capability into Foswiki. That would, in principle, encompass all of the rendering process.

A full explain would show you how your viewed page was constructed by Foswiki phase by phase. This would be a useful debugging and learning tool.

Implementing this is an important step in this direction.

I must raise a feature request to cover the general 'explain' concept.

-- JulianLevens - 23 Oct 2012

i agree, explain is something we want going into the future. and this is one of those.

Kip - you're missing docco and unit tests - and then we can talk about formatting and how&where to use it

notes:

1. it may be useful for there to be an ACL - to limit what the curious can find out
2. i think that in the non-DENY case, it'll be safe, but if a topic is VIEW DENIED, its preferences have been evaluated, but the user should not know about it.

-- SvenDowideit - 23 Oct 2012

Hi guys, thanks for the comments. Sorry that I have been slow to respond - been quite busy. I am removing myself as a committed developer for now, because I don't think that this is a fully formed idea yet. Also because I will be on vacation for a few weeks. I don't like the idea of creating another single-purpose macro called 'VARIABLESTACK', and going along with Julian's idea ... maybe we can have an %EXPLAIN% macro which would hold this code. It could use a mechanism similar to %INCLUDE%'s includeHandlers

%EXPLAIN{what="Preferences" web="%WEB%" topic="%TOPIC%"
    action="showStackTopics"}%

%EXPLAIN{what="Preferences" web="%WEB%" topic="%TOPIC%"
    action="showAllSettings" macro="MY_MACRO"}%
--> returns a table containing all values for %<nop>MY_MACRO% at all levels, with an asterisk next to the one that gets priority

And perhaps we could have these requests handled by Foswiki::ExplainHandlers::Preferences.pm. I don't know what Julian's full 'explain' idea is, but it might be useful to expose things via a TML macro.

@SD - I don't think any security checks are needed as the macro is not revealing non-public information. I.e. %VARIABLESTACK% displayed on Gothams.WebHome will return

DefaultPreferences,Main.SitePreferences,Main.KipLubliner,Gothams.WebPreferences,Gothams.WebHome,ANON

But all this information can be determined by a careful study of PreferenceSettings (now that George has fixed the doc!).

-- KipLubliner - 26 Oct 2012

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