Nevermind, this definitely seems to be the right approach (single 
parameter).  I guess I was just misreading the documentation, the section I 
was looking at was describing how to create one of these objects I think.

Regardless, the lua filtering is super cool :)

On Wednesday, January 9, 2019 at 7:49:45 PM UTC-8, sjm...-HmMyXyqgL2CVc3sceRu5cw@public.gmane.org wrote:
>
> Thank you John, this is indeed much simpler than I was making it.
>
> Comparing with some of the example filters, when overriding these I should 
> basically always be doing `SomePandocThing(el)` where there's just one `el` 
> parameter?
>
> Thanks again!
>
> On Wednesday, January 9, 2019 at 12:08:33 PM UTC-8, John MacFarlane wrote:
>>
>>
>> Try this: 
>>
>> function Header(el) 
>>   if FORMAT == "beamer" then 
>>     table.insert(el.classes, "fragile") 
>>     return el 
>>   end 
>> end 
>>
>> sjm...-HmMyXyqgL2CVc3sceRu5cw@public.gmane.org writes: 
>>
>> > Hello, 
>> > 
>> > I am trying to create a very simple lua filter for beamer presentations 
>> > that will always make sure that 'fragile' is added to a frame (to 
>> satisfy 
>> > minted, which i use for inline teletype text and code blocks). I think 
>> I 
>> > can figure out the lua specifics of figuring out how to first check the 
>> > list for `fragile` and if not found then add it, but where I'm stuck is 
>> > more basic.  I can't figure out what my signature should even be here. 
>> > 
>> > if FORMAT == "beamer" or FORMAT == "latex" then 
>> >     function Header(level, content, attr) 
>> >         return pandoc.Header(level, content, attr) 
>> >         -- return pandoc.RawBlock('latex', 'hahahaha') -- works hehehe 
>> >     end 
>> > end 
>> > 
>> > 
>> > I wanted to just shadow it.  So with a simple test file `test.md` 
>> > 
>> > # Section 1 
>> > 
>> > ## This is Stuff {.fragile} 
>> > 
>> > - Look at this list 
>> > - Is it not nice? 
>> > 
>> > Yes it is. 
>> > 
>> > ## More Stuff {.allowframebreaks} 
>> > 
>> > 1. An ordered listing. 
>> > 2. Is even more nice. 
>> > 3. Depending on the context 
>> > 
>> > Running my simple filter gives 
>> > 
>> > pandoc -t beamer --lua-filter fragile_headers.lua test.md 
>> > Error running filter fragile_headers.lua: 
>> > [string "--[[..."]:208: Constructor for Header failed: [string 
>> "--[[..."]: 
>> > 239: attempt to index a nil value (local 'x') 
>> > 
>> > stack traceback: 
>> >         [C]: in function 'error' 
>> >         [string "--[[..."]:208: in function <[string "--[[..."]:203> 
>> >         (...tail calls...) 
>> > 
>> > 
>> > I was going off of what I thought the signature was for Header in the 
>> docs 
>> > here: https://pandoc.org/lua-filters.html#blocks 
>> > 
>> > But it seems like `attr` is optional? 
>> > 
>> > I couldn't find any Header examples in the repo, and I'm really lost. 
>>  I 
>> > feel like this is way easier than I'm making it, but what I wanted to 
>> do 
>> > was just append "fragile" in there.  Then add in features like checking 
>> if 
>> > `level` is equal to 2, and don't add it if it's already there.  But I 
>> don't 
>> > know how to get started.  Is the `function Header` signature even 
>> correct? 
>> > 
>> > Thanks for any thoughts for somebody who has spent an embarrassing 
>> amount 
>> > of time trying to figure this out. 
>> > 
>> > -- 
>> > You received this message because you are subscribed to the Google 
>> Groups "pandoc-discuss" group. 
>> > To unsubscribe from this group and stop receiving emails from it, send 
>> an email to pandoc-discus...-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org 
>> > To post to this group, send email to pandoc-...-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org 
>> > To view this discussion on the web visit 
>> https://groups.google.com/d/msgid/pandoc-discuss/b82d1c59-8f03-49df-ae3d-28bb92c63e57%40googlegroups.com. 
>>
>> > For more options, visit https://groups.google.com/d/optout. 
>>
>

-- 
You received this message because you are subscribed to the Google Groups "pandoc-discuss" group.
To unsubscribe from this group and stop receiving emails from it, send an email to pandoc-discuss+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To post to this group, send email to pandoc-discuss-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To view this discussion on the web visit https://groups.google.com/d/msgid/pandoc-discuss/5f29ee8e-3481-446d-8a95-f488cedf2fae%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.