Trim instructions. TrimRd chunk might need TrimL. Trim tests.

2 files changed, 44 insertions, 6 deletions

diff --git a/src/Hakyll/Web/Template.hs b/src/Hakyll/Web/Template.hs
index 204878c..13d5d35 100644
--- a/src/Hakyll/Web/Template.hs
+++ b/src/Hakyll/Web/Template.hs
@@ -115,6 +115,29 @@
 -- That is, calling @$partial$@ is equivalent to just copying and pasting
 -- template code.
 --
+-- In the examples above you can see that outputs contain a lot of leftover
+-- whitespace that you may wish to remove. Using @'$-'@ or @'-$'@ instead of
+-- @'$'@ in a macro strips all whitespace to the left or right of that clause
+-- respectively. Given the context
+--
+-- > listField "counts" (field "count" (return . itemBody))
+-- >    (sequence [makeItem "3", makeItem "2", makeItem "1"])
+--
+-- and a template
+--
+-- > <p>
+-- >     $for(counts)-$
+-- >       $count$
+-- >       $-sep-$...
+-- >     $-endfor$
+-- > </p>
+--
+-- the resulting page would look like
+--
+-- > <p>
+-- >     3...2...1
+-- > </p>
+--
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE ScopedTypeVariables        #-}
 module Hakyll.Web.Template
@@ -209,10 +232,17 @@ applyTemplate' tes context x = go tes
 
     go = fmap concat . mapM applyElem
 
+    trimError = error $ "Hakyll.Web.Template.applyTemplate: template not " ++
+        "fully trimmed."
+
     ---------------------------------------------------------------------------
 
     applyElem :: TemplateElement -> Compiler String
 
+    applyElem TrimL = trimError
+
+    applyElem TrimR = trimError
+
     applyElem (Chunk c) = return c
 
     applyElem (Expr e) = applyExpr e >>= getString e
diff --git a/src/Hakyll/Web/Template/Trim.hs b/src/Hakyll/Web/Template/Trim.hs
index 4ea3438..bc7e691 100644
--- a/src/Hakyll/Web/Template/Trim.hs
+++ b/src/Hakyll/Web/Template/Trim.hs
@@ -1,5 +1,5 @@
 --------------------------------------------------------------------------------
--- | Module for trimming whitespace.
+-- | Module for trimming whitespace
 module Hakyll.Web.Template.Trim
     ( trim
     ) where
@@ -20,15 +20,22 @@ trim = cleanse . canonicalize
 
 
 --------------------------------------------------------------------------------
+-- | Apply the Trim nodes to the Chunks.
 cleanse :: [TemplateElement] -> [TemplateElement]
 cleanse = recurse cleanse . process
     where process [] = []
-          process (TrimR:Chunk str:ts) = Chunk (lstrip str):process ts
-          process (Chunk str:TrimL:ts) = Chunk (rstrip str):process ts
-          process (t:ts) = t:process ts
+          process (TrimR:Chunk str:ts) = let str' = dropWhile isSpace str
+                                         in if null str'
+                                                then process ts
+                                                -- Might need to TrimL.
+                                                else process $ Chunk str':ts
+
+          process (Chunk str:TrimL:ts) = let str' = dropWhileEnd isSpace str
+                                         in if null str'
+                                                then process ts
+                                                else Chunk str':process ts
 
-          lstrip = dropWhile isSpace
-          rstrip = dropWhileEnd isSpace
+          process (t:ts) = t:process ts
 
 --------------------------------------------------------------------------------
 -- | Enforce the invariant that:
@@ -75,6 +82,7 @@ dedupe = recurse dedupe . process
 
 
 --------------------------------------------------------------------------------
+-- | @'recurse' f t@ applies f to every '[TemplateElement]' in t.
 recurse :: ([TemplateElement] -> [TemplateElement])
         -> [TemplateElement]
         -> [TemplateElement]