Conditional $if statements

[badlydrawnrob]

A Google Ai summary said $if(body-id == "home")$ was valid but I'm getting the following error:

Error compiling template "./source/pandoc/template.html" (line 57, column 18):
unexpected " "
expecting ".", "/" or ")"

So I'm assuming that's not valid at all. It would be handy if I don't need another YAML value though. Any ideas?

[rnwst]

I don't think this is currently possible to do in templates. There is already a feature request for this functionality: jgm/doctemplates/issues/29

[jgm]

AI is making it up. Your authoritative source is the documentation:
https://pandoc.org/MANUAL.html#templates

[jgm]

So I'm assuming that's not valid at all. It would be handy if I don't need another YAML value though. Any ideas?

Somewhat complex, but you could query your metadata and construct a new variable based on that using --variable. Should be possible all on one command line. With bash you can do something like this, where test.md is the file you're processing:

pandoc $([[ "$(pandoc --template <(echo '$meta-json$') test.md | jq -r '.["body-id"]')" = "home" ]] && echo "--variable-json=foo=true" || echo "--variable-json=foo=false")

This will set the template variable foo to true if body-id == home.

[iandol]

See also #3697 -- the discussion there ventures into the idea of allowing a templating language so that e.g. lua templates are optionally saved, and pandoc's lua engine preparses these before pandoc uses them...

[badlydrawnrob]

@jgm Ah. I've used JQ before. I generally stick to code that's simple enough to remember and adjust later; my terminal skills are light! (presumably you'd wrap template content with $if(foo)).

I'll just add it as a YAML tag for now. I only need it for a single page, so a simple scripting option like mustache (as in other issue) would definitely be welcomed with equality etc. I do think it's wise to limit features of Pandoc though, I already find the documentation tricky to pinpoint what I want sometimes.

I'm purposefully using Pandoc for a simple website as it's easier to use than, say, https://www.11ty.dev/ or Zola. I just need a way to loop through the compiled files and output a list of posts (I'm sure there's a bash command for that). So yeah, templating for those reasons.

[jgm]

Actually jq isn't even necessary. This is simpler:

 pandoc $([[ "$(pandoc --template <(echo '$body-id$') test.md)" = "home" ]] && echo "--variable-json=foo=true" || echo "--variable-json=foo=false")

[badlydrawnrob]

If no VAL is specified, the key will be given the value true (documentation)

Even simpler is just --variable=call-to-action! Avoids me having to declare it in the YAML.

[badlydrawnrob]

One other thing I am struggling with is how to use $npm-package-version to cache-bust .css?v= and neither (a) --version-json css-version=$(npm pkg get version) or (b) --variable-json css-version=$(echo $npm_package_version) works ...

(a) errors

-- href="$css$?v=$css-version$" in the template
Error compiling template "./source/pandoc/template.html" (line 57, column 18):
unexpected " "

(b) errors

Could not parse '2.5.0' as JSON:
Trailing garbage

[jgm]

(a) should work. An error compiling the template has nothing to do with the variable. Check your template syntax? (specifically the space at "./source/pandoc/template.html" (line 57, column 18))

href="$css$?v=$css-version$"

should be fine but maybe there's a problem elsewhere?
Also, try using quotes:

--variable-json css-version="$(npm pkg get version)"

[badlydrawnrob]

@jgm Great thanks!

It was the second option that solved it ... but for npm script you have to escape those quotes. It's funny how concatenation works here, as that command returns a "2.5.0" version string anyway:

--variable-json css-version=\"$(npm pkg get version)\"

I was changing that version manually before, like a mug 😉