haskell - How to use Pandoc filter within Hakyll? -

i sorry ask such question. new haskell. searched internet whole day didn't find example.

i have pandoc filter written in python (tikzcd.py). want use filter process blog posts.

i guess need use unixfilter or pandoccompilewithtransform knowledge haskell not enough find solution myself.

so, provide me example?

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@michael gives solution using pandoccompilewithtransformm , unixfilter. works. there problem.

when using filter command line,

pandoc -t json -readeroptions input.markdown | ./filter.py | pandoc -f json -writeroptions -o output.html 

or equivalently

pandoc --filter ./filter.py -readeroptions -writeroptions -o html 

this command shorter doesn't show procedures.

but pandoccompilertransformm, like

pandoc -t html -readeroptions -writeroptions input.mardown | pandoc -t json | ./filter.py | pandoc -f json -writeroptions -o output.html 

the difference text passed filter.py different: 1 contents directly produced markdown, while other texts produced html produced markdown. know, convert , forth produce unexpected problem. think there may better solution.

ps. i've stared learn haskell. hope solve problem myself someday. thank you!

in end think use both. using https://github.com/listx/listx_blog/blob/master/blog.hs model, following have same shape transformer has in it. transformer used on lines 69-80 'posts' -- third argument pandoccompilerwithtransformm, (pandoc -> compiler pandoc) here need add absolute path python filter -- or name if it's in $path -- , reader , writer options (e.g. defaulthakyllreaderoptions , defaulthakyllwriteroptions)

import text.pandoc import hakyll  type script = string   transformer   :: script         -- e.g. "/absolute/path/filter.py"   -> readeroptions  -- e.g.  defaulthakyllreaderoptions   -> writeroptions  -- e.g.  defaulthakyllwriteroptions   -> (pandoc -> compiler pandoc) transformer script reader_opts writer_opts pandoc =      let input_json = writejson writer_opts pandoc        output_json <- unixfilter script [] input_json        return $            -- either (error.show) id $  -- line needs uncommented atm.           readjson reader_opts output_json  

similarly, (transformer "/usr/local/bin/myfilter.py" defaulthakyllreaderoptions defaulthakyllwriteroptions) might used (return . pandoctransform) used, on line 125 of example gist

---

for debugging might outsource unixfilter:

transform :: script -> string -> compiler string transform script md = json0 <- unixfilter pandoc input_args md                          json1 <- unixfilter script [] json0                          unixfilter pandoc output_args json1     pandoc = "pandoc"    input_args = words "-f markdown -t json" -- add others    output_args = words "-f json -t html"    -- add others 

the 3 lines of do block equivalent of stages of unix piping in pandoc -t json | filter.py | pandoc -f json whatever additional arguments.

---

i think maybe right there layer of pandoc , forth here. pandoccompilerwithtransform(m) functions direct pandoc-> pandoc function - applied pandoc hakyll comes with. think should dispense , use pandoc libraries directly. use of unixcompile might this.

transformxlvi :: script -> readeroptions -> writeroptions -> string  -> compiler html transformxlvi script ropts wopts = fmap fromjson . unixfilter script [] . tojson         tojson   = writejson wopts      --           . either (error . show) id -- pandoc > 1.14                . readmarkdown ropts      fromjson = writehtml wopts     --           . either (error . show) id                . readjson ropts  

i hope principles emerging these variations! should pretty same preceding transform; using pandoc library in place of calls pandoc executable.