On trello at https://trello.com/c/wlMdpHju/

Another example here.

@Gerardduenas Thanks for bumping this ticket. We'll talk about it at the team's next estimation meeting.

Parsoid API now has support for subst-ing of templates ( https://gerrit.wikimedia.org/r/#/c/208993/ ) which Flow could use for this purpose. We are yet to update our API docs.

Change 218574 had a related patch set uploaded (by Catrope):
Run pre-save transform on wikitext before saving it

https://gerrit.wikimedia.org/r/218574

And please check
to in header of a topic when creating or changing first subst transform , and then save

see subst:CONTENTLANG in https://ru.wikipedia.org/wiki/%D0%A2%D0%B5%D0%BC%D0%B0:Shhqnuw5kngudt55

Change 218574 merged by jenkins-bot:
Run pre-save transform on wikitext before saving it

https://gerrit.wikimedia.org/r/218574

• https://gerrit.wikimedia.org/r/218574 (branch master): WMF-deploy-2015-06-16_(1.26wmf10)

Checked on http://en.wikipedia.beta.wmflabs.org/wiki/.

• checked the example from the comment: https://ca.wikipedia.org/w/index.php?title=Topic:Sgp7ruir8pf4ejec&topic_showPostId=sgp7ruiucyaf2wtw#flow-post-sgp7ruiucyaf2wtw

{{subst:#ifeq:{{subst:CONTENTLANG}}|en||''Apologies for writing in English, please help translate this into your local language.''}}

results in

• checked couple of examples from https://www.mediawiki.org/wiki/Manual:Substitution: e.g. {{subst:UC:{{subst:CURRENTDAYNAME}}}} results in DIMECRES

However, I am not sure that the following is expected:

• {{subst:Discussió:ET1}} results in the error message <span class="error">Discussions cannot be embedded yet.</span>
• {{subst:Portada}} results in

{{Introducció de la portada}}
{| border="0" style="margin-top: 5px;"
| width="60%" valign="top" style="padding-right: 5px;" |
{{Metacaixa elements enciclopèdics a la portada|
|{{{1}}}=seleccionada
|Secció={{{1}}}
|Dependència={{{2}}}
}}{{Metacaixa elements sobre la Viquipèdia a la portada|
|{{{2}}}=seleccionada
|Secció={{{2}}}
|Dependència={{{1}}}
}}
| width="40%" valign="top" style="padding-left: 5px;" | {{Categories|una columna}}
|}
__NOTOC__ __NOEDITSECTION__

@DannyH When it comes to Wikipedia?
ru-wiki 1.26wmf10 (rMW3e9c6676ef83) 01:57, 17 06 2015 but
substitution not yet working https://ru.wikipedia.org/wiki/%D0%A2%D0%B5%D0%BC%D0%B0:Sjkk3xqrgi2u68rs

Unfortunately, Forrestbot was wrong (T103291: Forrestbot posted wrong release branch).

This is not in any release branches yet.

Also, it will not apply to topic titles like https://ru.wikipedia.org/wiki/%D0%A2%D0%B5%D0%BC%D0%B0:Shhqnuw5kngudt55 . Flow topic titles do not support wikitext.

In T68307#1376343, @Etonkovidova wrote:

However, I am not sure that the following is expected:

• {{subst:Discussió:ET1}} results in the error message <span class="error">Discussions cannot be embedded yet.</span>

This is expected. Subst-ing in a Flow board is not possible. Transcluding a discussion could make sense (but would require some careful consideration of the feature), but substing probably wouldn't.

• {{subst:Portada}} results in

This template probably just isn't intended to be subst-ed. But that template doesn't exist, and I don't get that result at either http://en.wikipedia.beta.wmflabs.org/wiki/Topic:Sjoxzoqv6drmilg8 or http://en.wikipedia.beta.wmflabs.org/w/index.php?title=Sandbox&oldid=229341