How to write tests for a lua filter

[RudolfVonKrugstein]

Hi,

I am trying to write tests using busted for a lua filter for pandoc, and I am unable to get the tests and using the filter by pandoc to work at the same time.
I think I can break it down to something documented here not working:

When I do:

function CodeBlock(el)
  print("code block")
  return el
end

It works, by which I mean: I can see the output "code block" when compiling a markdown with a code block using this filter.
But when I do:

return {
	CodeBlock = function(el)
		print("code block")
		return CodeBlock(el)
	end,
}

pandoc does not pick up on CodeBlock (I cannot see the output).

But, my problem is that I cannot get the first version to work for testing with busted because I am unable to import the module as a simple require does not work.

My pandoc version:

> pandoc --version
pandoc 3.1.11.1
Features: +server +lua
Scripting engine: Lua 5.4
User data directory: /home/nathan/.local/share/pandoc
Copyright (C) 2006-2023 John MacFarlane. Web: https://pandoc.org
This is free software; see the source for copying conditions. There is no
warranty, not even for merchantability or fitness for a particular purpose.

Thanks for any help!

[jgm]

Do you want return pandoc.CodeBlock(el) ?

[RudolfVonKrugstein]

But if I just write

return {
	{
		CodeBlock = function(el)
			print("code block")
			return el
		end,
	},
}

it works! Is the documentation here incorrect?

[jgm]

Check the documentation for pandoc.CodeBlock. The argument is presumably supposed to be some text, not a pandoc element.

[RudolfVonKrugstein]

Sorry, I don't seem to be clear.

If I write:

return {
	CodeBlock = function(el)
		print("code block")
		-- some other code
	end,
}

the function never gets called, even so I do have CodeBlocks in my document.

But if I write:

return {
	{
		CodeBlock = function(el)
			print("code block")
			-- some other code
		end,
	},
}

or

function CodeBlock(el)
  print("code block")
  -- some other code
end

The function does get called.
But according to this, all examples (including the first one) should work.

[jgm]

The first one will work in pandoc 3.5 but not earlier versions.

[RudolfVonKrugstein]

ah ok, thank your for the help!

[tarleb]

As an answer to the general question of how to test filters: I asked myself the same thing, and ended up writing perevir for that. It's work in progress, but it's already serving me well.

[RudolfVonKrugstein]

Uh, thanks!