You could take full control of the output by creating the desired block yourself.

E.g., instead of local cb = pandoc.CodeBlock() ff., you could write

return pandoc.RawBlock('markdown',
  string.format('``` math\n%s\n```\n', text)
)

So you'd basically be creating the Markdown yourself, which is
relatively safe in the case of code blocks (assuming that the math
doesn't contain ```, which would be very unusual).

HTH,
Albert


'Angel Joaniquet' via pandoc-discuss <pandoc-discuss-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org> writes:

> cross-posting of
> https://stackoverflow.com/questions/67109880/is-it-posible-to-enable-extensions-on-pandoc-filters#comment118648930_67109880
>
> The reason is that I want to have all in one file, to diminish the
> cognitive load
>
>
> El viernes, 16 de abril de 2021 a las 13:41:58 UTC+2, mb21 escribió:
>
>> cross-posting of
>> https://stackoverflow.com/questions/67109880/is-it-posible-to-enable-extensions-on-pandoc-filters
>>
>> Why do you prefer to set this in the filter instead of on the writer? I
>> don't think there's a way to do that... because the filter just outputs an
>> AST again, and what you're trying to change is happening in the writer...
>>
>> On Thursday, April 15, 2021 at 4:20:32 PM UTC+2 Angel Joaniquet wrote:
>>
>>> The lua split function is this
>>>
>>>
>>> ```lua
>>> function split(str,pat)
>>>    local tbl = {}
>>>    str:gsub(pat, function(x) tbl[#tbl+1]=x end)
>>>    return tbl
>>> end
>>> ```
>>>
>>> El jueves, 15 de abril de 2021 a las 16:08:23 UTC+2, Angel Joaniquet
>>> escribió:
>>>
>>>>
>>>> I'm trying to make a filter to transform some features of org-mode to
>>>> GitLab-markdown (not supported by Pandoc out of the box), in particular,
>>>> the math blocks.
>>>>
>>>> The filter should work when transforming to `markdown`, but instead of
>>>> giving the markdown format for the math blocks (enclosed by `$$...$$`), it
>>>> should write the blocks as
>>>>
>>>>     ```  math
>>>>     a + b = c
>>>>     ```
>>>>
>>>> The preces I have now is
>>>>
>>>> In org-mode, the math blocks are simply the latex code:
>>>>
>>>> ```
>>>> \begin{equation}
>>>> a + b = c
>>>> \end{equation}
>>>> ```
>>>>
>>>> this is parsed as a pandoc AST `RawBlock` with format `latex`. I then
>>>> remove the first (`\begin{equation}`) an last line (`\end{equation}`), and
>>>> construct a pandoc `CodeBlock` with atrributes `{"math"}`, so the
>>>> `CodeBlock` object displays in AST as
>>>>
>>>> ```
>>>> CodeBlock ("",["math"],[]) "a + b = c\n"
>>>> ```
>>>>
>>>> and then I let Pandoc create the markdown document, and the written
>>>> result is
>>>>
>>>>     ``` {.math}
>>>>     a + b = c
>>>>     ```
>>>>
>>>>
>>>>
>>>> **The question:**
>>>> I want the bare `math`, not `{.math}` written, without the use of CLI
>>>> options.
>>>>
>>>>
>>>> I am aware that this can be done setting the Writer extension
>>>> `fenced_code_attributes` to false (eg. `$pandoc -w
>>>> markdown-fenced_code_attributes ...`), but I would much prefer this done
>>>> inside the filter.
>>>>
>>>> Or is it possible to set the extensions inside the filter?
>>>>
>>>>
>>>> Here is my atempted lua-filter:
>>>>
>>>> ``` lua
>>>> function RawBlock(rb)
>>>>    if rb.format == "latex" then
>>>>       local text = rb.text
>>>>       split_text =  split(text, "[^\n]*")
>>>>       if split_text[1] == '\\begin{equation}'  and
>>>> split_text[#split_text-1] == '\\end{equation}' then
>>>>          table.remove(split_text, #split_text-1)
>>>>          table.remove(split_text, 1)
>>>>          text = table.concat(split_text, "\n")
>>>>          local cb = pandoc.CodeBlock()
>>>>          cb.attr = {"",{"math"}}
>>>>          cb.text = text
>>>>          return cb
>>>>       end
>>>>    end
>>>> end
>>>> ```
>>>>
>>>>
>>>> Kind regards,
>>>>
>>>> Angel
>>>>
>>>>
>>>>
>>>>
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--
Albert Krewinkel
GPG: 8eed e3e2 e8c5 6f18 81fe  e836 388d c0b2 1f63 1124

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