From b54212c7e2b8a84f95815e93a13223e1525c4f85 Mon Sep 17 00:00:00 2001
From: Norman Liu <57917002+dreamsmasher@users.noreply.github.com>
Date: Thu, 11 Mar 2021 16:38:21 -0500
Subject: Add `renderPandocWithTransform` and `renderPandocWithTransformM`

* added function that allows for pre-pandoc transformations

* modified haddock docstring

* refactoring to avoid importing the kleisli fish

* Renamed `applyPandoc` to `renderPandocWithTransformM`, added non-monadic
variant. Exported previous new functions that I forgot to export.
---
 lib/Hakyll/Web/Pandoc.hs | 33 ++++++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/lib/Hakyll/Web/Pandoc.hs b/lib/Hakyll/Web/Pandoc.hs
index 5f04de4..372465b 100644
--- a/lib/Hakyll/Web/Pandoc.hs
+++ b/lib/Hakyll/Web/Pandoc.hs
@@ -8,6 +8,8 @@ module Hakyll.Web.Pandoc
     , writePandocWith
     , renderPandoc
     , renderPandocWith
+    , renderPandocWithTransform
+    , renderPandocWithTransformM
 
       -- * Derived compilers
     , pandocCompiler
@@ -103,6 +105,32 @@ renderPandocWith ropt wopt item =
     writePandocWith wopt <$> readPandocWith ropt item
 
 
+--------------------------------------------------------------------------------
+-- | An extension of `renderPandocWith`, which allows you to specify a custom
+-- Pandoc transformation on the input `Item`.
+-- Useful if you want to do your own transformations before running 
+-- custom Pandoc transformations, e.g. using a `funcField` to transform raw content.
+renderPandocWithTransform :: ReaderOptions -> WriterOptions
+                    -> (Pandoc -> Pandoc)
+                    -> Item String
+                    -> Compiler (Item String)
+renderPandocWithTransform ropt wopt f = 
+    renderPandocWithTransformM ropt wopt (return . f) 
+
+
+--------------------------------------------------------------------------------
+-- | Similar to `renderPandocWithTransform`, but the Pandoc transformation is
+-- monadic. This is useful when you want the pandoc
+-- transformation to use the `Compiler` information such as routes,
+-- metadata, etc. along with your own transformations beforehand.
+renderPandocWithTransformM :: ReaderOptions -> WriterOptions
+                    -> (Pandoc -> Compiler Pandoc)
+                    -> Item String
+                    -> Compiler (Item String)
+renderPandocWithTransformM ropt wopt f i = 
+    writePandocWith wopt <$> (traverse f =<< readPandocWith ropt i) 
+
+
 --------------------------------------------------------------------------------
 -- | Read a page render using pandoc
 pandocCompiler :: Compiler (Item String)
@@ -137,9 +165,8 @@ pandocCompilerWithTransform ropt wopt f =
 pandocCompilerWithTransformM :: ReaderOptions -> WriterOptions
                     -> (Pandoc -> Compiler Pandoc)
                     -> Compiler (Item String)
-pandocCompilerWithTransformM ropt wopt f =
-    writePandocWith wopt <$>
-        (traverse f =<< readPandocWith ropt =<< getResourceBody)
+pandocCompilerWithTransformM ropt wopt f = 
+    getResourceBody >>= renderPandocWithTransformM ropt wopt f
 
 
 --------------------------------------------------------------------------------
-- 
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