Generating markdown tables in Haskell with Pandoc - haskell

Question

I am trying to create tables directly using the Pandoc AST. I am trying a couple of approaches. However, nothing seems to be working. Rather than getting a table output, I just get [TABLE]. I have tried both the Pandoc builder monad, as well as directly creating a Table using the primitive constructors. I am not sure what I am getting wrong here.
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE DuplicateRecordFields #-}
{-# LANGUAGE ScopedTypeVariables #-}
module Main where
import Lib
import Data.Text (Text)
import qualified Data.Text as T
----------------------------------------
-- Pandoc imports
import Text.Pandoc
import Text.Pandoc.Builder
import Text.Pandoc.Options
import Text.Pandoc.Writers.Markdown
testTable :: IO ()
testTable = do
let my_tab = simpleTable [plain "Column 1"] [[plain "hello there"], [plain "hello there 2"], [plain "hello there 2"]]
let tab2 = Table [] [AlignDefault] [0.0] [[Plain [Str "Column",Space,Str "1"]]] [[[Plain [Str "Hello",Space,Str "there"]]] ,[[Plain [Str "Hello",Space,Str "there",Space,Str "2"]]] ,[[Plain [Str "Hello",Space,Str "there",Space,Str "3"]]]]
let other_tab = simpleTable colHeaders [testRow, testRow]
let thing = setTitle "Test report" $ doc $ para "Hey there" <> my_tab <> para "paragraph after table" <> singleton tab2 <> other_tab
md' <- runIO (writeMarkdown def thing)
case md' of
Left _ -> print "Damn"
Right md -> writeFile "my.md" (T.unpack md)
-- https://www.gwern.net/haskell/goodreadsToMarkdown.hs
colHeaders :: [Blocks]
colHeaders = map singleton [ Plain [Str "Title"]
, Plain [Str "Author"]
]
testRow = map singleton [ Plain [Str "Col 1"]
, Plain [Str "Col 2"]
]
main :: IO ()
main = do
print "hello"
testTable
let headers = map (plain . text) ["foo", "bar"]
let rows = map (map (plain . text)) [["1", "2"], ["3", "4"]]
-- md' <- runIO (writeMarkdown def (doc (simpleTable headers rows)))
let caption' = text "Hello"
md' <- runIO (writeMarkdown def (doc (table caption' [(AlignLeft, 1.0), (AlignLeft, 1.0)] headers rows)))
case md' of
Left _ -> print "Damn"
Right md -> print md

Answer 1

Markdown, by default, does not support tables. Pandoc implements multiple ways to output tables, but this has to be enabled. The easiest way is to use the set of extensions that make up pandoc flavored Markdown.
Instead of writeMarkdown def thing, you can write
writeMarkdown (def{writerExtensions = pandocExtensions}) thing
Now your program produces tables using one of pandoc's table extensions.