Help Wanted - Filtered transclusion

[TW Tones]

Folks,

I can work out what is happening here, at least a second set of eyes would be appreciated

I have a filtered transclusion as follows

{{{ [<local-value>] ~[<global-config-value>] ~[<config-default>] }}}

Each of the variables therein are set using a $set widget (more details below)

Unfortunately the second result global-config-value is never the result if there is no local-value

The following is how I get the global-config-value and it works as below

<$set name=config-tiddler value={{{ [[$config-name$]addprefix[$:/config/]] }}}>
<$set name=global-config-value value={{{ [<config-tiddler>get[text]] }}}>


:global-config-value=<<global-config-value>><!--returns the correct value here but never responds to this value in the filtered transclusion.

Yet when I try and use the filtered transclusion above, specifically  ~[<global-config-value>]
It never seems to work.

I have tried to wikify the value first with no success

I have looked at this many times and cant see what is wrong.

Thanks in advance if you can help

Tones

[Eric Shulman]

On Sunday, November 8, 2020 at 4:25:07 PM UTC-8, TW Tones wrote:

I have a filtered transclusion as follows

{{{ [<local-value>] ~[<global-config-value>] ~[<config-default>] }}}

Each of the variables therein are set using a $set widget (more details below)

Unfortunately the second result global-config-value is never the result if there is no local-value

You have three runs, using an implied "OR", with the expectation that they are evaluated left-to-right, until a value is found.

I'm not 100% certain why the above syntax doesn't do that.  But you might try using else<...> instead:

{{{ [<local-value>else<global-config-value>else<config-default>] }}}

-e 

[TW Tones]

Eric,

Thanks for the suggestion But it has not solved it. It is almost as if when used in the filter else goes bad

This proves the values are being populated

:1 {{{ [<local-value>] }}}

:2 {{{ [<global-config-value>] }}}

:3 {{{ [<config-default>] }}}

But something is still going wrong as all three of these return the value in <<local-value>>

1: {{{ [<local-value>] }}} returns a value is set

4:{{{ [<local-value>else[other]]  }}}

5:{{{ [<local-value>] ~[[other]]  }}}

Weird

Tones

[Saq Imtiaz]

How are you setting

<local-value>

?

I suspect it never returns an empty list, and therefore the else clause is never triggered.

For example, the following will never trigger an else clause when used in a filter, as it will never return an empty list:

<$set name=config-tiddler value={{{ [[$config-name$]addprefix[$:/config/]] }}}>

Assuming that each filter run returns an empty list when it should not be used, you can also use the form:

{{{ [<local-value>] [<global-config-value>] [<config-default>] +[first[]] }}}

[TW Tones]

Saq,

Thanks fort the tip, yes I tried that. I will review again with a fresh look, but it is confusing me.

I am wondering if there is some sort of regression or bug here?

I suppose in the mean time if I can find an alternative, perhaps with list filters and not filtered transclusions it would be fine, however it does seem like a source of hours of frustration.

I will share back any learnings.

Without solving why the former did not work this is a working version.

\define get-config(name)
{{{ [all[current]get[$name$]] ~[[$:/config/$name$]get[text]] ~[[$:/config/$name$]get[config-values]split[ ]first[]] }}}<br>
\end
<<get-config test-config>>

However from experience if I wish to access the result in a list filter I will first need to wikify  

<<get-config test-config>>

Which makes the code messy.

Regards

Tones

[Saq Imtiaz]

You may have missed my point. I don't believe your first filter run ever returns an empty title list.

Try this:

{{{ [<local-value>!is[blank]] ~[<global-config-value>!is[blank]] ~[<config-default>] }}}

For a hint try this in Advanced Search -> Filters:

[<foo>]

It should tell you there is 1 match.

You can also test:

{{{ [<local-value>count[]] }}}

Your first filter run must return no titles in order for the else clause to be triggered.

If none of that works, please post the actual vs expected outcome of:

{{{ [<local-value>] [<global-config-value>] [<config-default>] }}}

[TW Tones]

Saq,

Thanks, I did understand your point, and expected <local-value> to be empty and could not make it so, Although '<<local-value>>' always returned '' when empty.

But as I read in the following example it appears to be blank? thus if !is[blank] no value will be returned and else is engaged.

Perhaps we can say an empty run is blank not empty?
Thus as you suggested !is[blank] changes blank to empty.

Thus in the case of [<varname>] an empty varname returns blank not empty.

I have decided to take another path, dynamically create a macro eg "\define setting() value"

This reply was Posted now, I forgot to post it yesterday.

Thanks for you help

Tones

[Saq Imtiaz]

The key thing to understand here is that unknown variables get assigned a value of "", i.e. a zero length string. The is[blank] operator checks specifically for zero length strings.

So <<missingvar>> won't show anything when wikified as you are rendering a zero length string, but the filter result is not an empty title list but rather has one member, a zero length string.