Re: Lua filter to convert Markdown comment

[Peter <pmatulis-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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This is really nice. Gratitude.

On Friday, 15 January 2021 at 04:19:51 UTC-5 BP wrote:

>
> Almost there. You need 
>
>
> `content = {pandoc.Str"Foo"}`
>
>
> since the content of a Header is a list of inline elements.
>
> As for multiple possible values Lua patterns are, as you seem to have 
> discovered, a bit challenged in that they don't support alternations. The 
> best solution is to use a table:
>
> ``````lua
> -- Localize `pandoc` to a shorter name to save space & type less!
> local p = pandoc
>
> -- This is your "substitution" table.
> local text4match = {
>   -- If you need styling do this:
>   foo = { p.Str"Foo", p.Space(), p.Str"and", p.Space(), 
> p.Emph(p.Str"more.") },
>   -- If you do not need styling you can do this:
>   bar = { p.Str"Bar and less." },
> }
>
> function RawBlock (elem)
>   local key = elem.text:match"%<%!%-%-%s*(%a+)%s*%-%-%>"
>   if key then
>     local text = text4match[key]
>     if text then
>       return p.Header(2, text)
>     end
>   end
>   -- No match, no text, ignore this elem
>   return nil
> end
> ``````
>
> HTH,
>
> /bpj
>
> -- 
> Better --help|less than helpless
>
> Den fre 15 jan. 2021 04:39Peter Matulis <pmat...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> skrev:
>
>> So I now have this:
>>
>> function RawBlock(el)
>>   if el.text:match("%<%!%-%- foo %-%-%>") then
>>     content = "foo"
>>     return pandoc.Header(2, content)
>>   end
>> end
>>
>> There are actually about a dozen such known Markdown comments (e.g. 
>> 'foo', 'bar').
>> Instead of creating multiple files I'd like to have just one that uses a 
>> regex and capture group:
>>
>>   if el.text:match("%<%!%-%- (%a+) %-%-%>") then
>>
>> I'm just unsure how to refer to the capture in a conditional statement
>> (i.e. "if 'foo' is captured then 'content' = "foo", elsif 'bar' is 
>> captured then 'content' = "bar").
>>
>>
>> On Thu, 14 Jan 2021 at 15:57, Peter Matulis <pmat...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>>
>>> Gratitude. This got me going.
>>>
>>> On Thu, 14 Jan 2021 at 13:52, John MacFarlane <j...-TVLZxgkOlNX2fBVCVOL8/A@public.gmane.org> wrote:
>>>
>>>>
>>>> What you want to do is match on a RawBlock element.
>>>> Something like
>>>>
>>>> function RawBlock(el)
>>>>   if el.text:match("<!--") then
>>>>     content = -- fill this in based on el.text
>>>>     return pandoc.Header(2, content)
>>>>   end
>>>> end
>>>>
>>>>
>>>> Peter Matulis <pmat...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes:
>>>>
>>>> > Hi. I'm new to Pandoc & Lua but my present issue is straightforward. 
>>>> I am
>>>> > converting a Markdown file to HTML with pandoc like this:
>>>> >
>>>> > pandoc -L filter.lua -f gfm -t html -o file.html file.md
>>>> >
>>>> > Where file.md contains a line with this MD comment (the MD file was
>>>> > obtained by converting from RST where I had to seed that file with an 
>>>> RST
>>>> > comment to use as a placeholder for what I'm doing here):
>>>> >
>>>> > <!-- blah -->
>>>> >
>>>> > I simply want to convert this into an actual (second-level) MD header:
>>>> >
>>>> > ## blah
>>>> >
>>>> > From what I've read, I would ideally specify an "element" that will be
>>>> > acted upon, but what is a comment considered? Anyway, I think I can 
>>>> specify
>>>> > `Pandoc` to mean "check the entire document", and that's what I've 
>>>> done
>>>> > here (I will eventually be iterating through multiple MD files so I 
>>>> should
>>>> > really not be doing it like this; please advise!):
>>>> >
>>>> > function Pandoc (value)
>>>> >   comment = "<!-- blah -->"
>>>> >   comment = comment:gsub("%<%!%-%- blah %-%-%>", "## blah")
>>>> >   return value
>>>> > end
>>>> >
>>>> > I've run the main logic through Lua on the terminal and it works:
>>>> >
>>>> > $ lua
>>>> > Lua 5.3.3  Copyright (C) 1994-2016 Lua.org, PUC-Rio
>>>> >> comment = "<!-- blah -->"
>>>> >> comment = comment:gsub("%<%!%-%- blah %-%-%>", "## blah")
>>>> >> print (comment)
>>>> > ## blah
>>>> >
>>>> > But I'm failing to integrate it with Pandoc (no change is registered 
>>>> in
>>>> > file.html). It's probably due to my misunderstanding of functions 
>>>> (not a
>>>> > programmer!).
>>>> >
>>>> > TIA.
>>>> >
>>>> > /pm
>>>> >
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>>>> .
>>>>
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