Return link if exists otherwise external link

[Mat]

In the readme of a plugin I want to link to a tiddler that is not part of the plugin. 

If that tiddler exists in the wiki, then the link should be a regular tiddlylink.

If the tiddler is missing then it should be an external url to where that tiddler can be found.

The following works, calling it with

<<linkOrExt "https://mywiki#mytiddler">> 

\define link() {{{ [<__url__>split[#]rest[]decodeuri[]join[ ]] }}}

\define linkOrExt(url)

<$list filter="""$url$ +[split[#]rest[]decodeuri[]join[ ]is[missing]]""" emptyMessage=<<link>>> <a href="""$url$""" rel="noopener noreferrer" target="_blank">{{!!title}}</a>

</$list>

\end

...but I am hoping for something more elegant that doesn't need the extra macro. And it seems silly I have to do the splitting twice. Maybe something with then or else can be used but I can't fully wrap my head around these operators. (I wish the else op could somehow enclose a full expression directly in the filter: "...else<this separate filter>" )

Note: Trying to avoid the extra macro by doing:

emptyMessage={{{ [<__url__>split[#]rest[]decodeuri[]join[ ]] }}}

...returns a textified title, but it needs to be a link.

Ideas anyone?

<:-)

[Saq Imtiaz]

Quick thought:

 (I wish the else op could somehow enclose a full expression directly in the filter: "...else<this separate filter>" )

 

Use a filter run prefix.

[... my first filter run..] :else[.. my other filter run...]

[Mat]

Saq Imtiaz wrote:

Use a filter run prefix.

Appreciated. That'll be useful in other cases but it turns out it was not relevant for this issue.

----------------

But formulating the problem that emptyMessage was not linkified did spark some thoughts so the current status is decent enough:

\define linkOrExt(url)

<$vars

   link={{{ $url$ +[split[#]rest[]decodeuri[]join[ ]] }}}

   lbrack="[["  rbrack="]]">

<$list

   filter="""[<link>is[missing]]"""

   emptyMessage={{{ [<link>addprefix<lbrack>addsuffix<rbrack>] }}} >

  <a href="""$url$""" rel="noopener noreferrer" target="_blank">{{!!title}}</a>

</$list>

</$vars>

\end

Decent enough.

Thank you.

<:-)

[Saq Imtiaz]

You could also try something like this (untested):

\define linkOrExt(url)

<$list filter="""$url$ +[split[#]rest[]decodeuri[]join[ ]!is[missing]]""" emptyMessage="""<a href=<<__url__>> rel="noopener noreferrer" target="_blank">{{!!title}}</a>"""> {{{ [<__url__>split[#]rest[]decodeuri[]join[ ]] }}} </$list>

\end

[Mat]

@Saq  - thanks, I actually tried that, but the problem is that emptyMessage doesn't know what {{!!title}} is, so to say. (It would be desirable that it did!)

<:-)

[Saq Imtiaz]

Hi Mat, are you sure about that? 

@Saq  - thanks, I actually tried that, but the problem is that emptyMessage doesn't know what {{!!title}} is, so to say. (It would be desirable that it did!)

 

{{!!title}} in emptyMessage will correspond to the title of the the currentTiddler variable outside the ListWidget. 

Perhaps explain what it is you expect when using {{!!title}} in emptyMessage.

 

[Mat]

>{{!!title}} in emptyMessage will correspond to the title of the the currentTiddler variable outside the ListWidget. 

>Perhaps explain what it is you expect when using {{!!title}} in emptyMessage.

Thanks for following up! Exactly, {{!!title}} would get the title outside the listwidget. What I want is for e.g the url "https://mywiki#mytiddler" to output [[mytiddler]] if it exists as tiddler, otherwise <a href="...">mytiddler</a> . The macrocall will (typically) appear in plugin readme tiddlers.

Does this make sense or do I misunderstand something? Thank you.

<:-)

[Saq Imtiaz]

That makes sense and yes it isn't how emptyMessage works, as the variable is only set by the ListWidget when the filter has a result.

 I had assumed from your code that you wanted {{!!title}} in the emptyMessage to mean you wanted the title of the currentTiddler as set outside the list widget.

I think constructing the title in a variable as you have done is the right way to approach this for readable code.

[Mohammad Rahmani]

Mat,

 How the URL shall be given as an encoded uri?

Best wishes

Mohammad

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[Mat]

Mohammad wrote:

 How the URL shall be given as an encoded uri?

See https://link-or-ext.tiddlyhost.com/

The macro is called like this

<<link-or-ext "https://tiddlywiki.com/#Working%20with%20TiddlyWiki">>

i.e the URL is just copy-pasted from some wiki. 

By the way, you who also create a lot of community stuff, might benefit from this. Its curren main "problem" is discussed here.

<:-)

[Mohammad Rahmani]

Thank you Mat! 

Nice addition!

Best wishes

Mohammad

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