From 9e07d1ba364ca401cc1c6f5704023b1df1006779 Mon Sep 17 00:00:00 2001
From: Jasper Van der Jeugt <jaspervdj@gmail.com>
Date: Wed, 9 Feb 2011 13:27:45 +0100
Subject: Template syntax: $foo → $foo$
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---
 src/Hakyll/Web/Template.hs          | 19 ++++++++++++-------
 src/Hakyll/Web/Template/Internal.hs |  6 +++---
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/src/Hakyll/Web/Template.hs b/src/Hakyll/Web/Template.hs
index b4f2ea5..06fa8d4 100644
--- a/src/Hakyll/Web/Template.hs
+++ b/src/Hakyll/Web/Template.hs
@@ -21,17 +21,22 @@ readTemplate = Template . readTemplate'
     readTemplate' [] = []
     readTemplate' string
         | "$$" `isPrefixOf` string =
-            let (key, rest) = readIdentifier $ drop 2 string
-            in Escaped key : readTemplate' rest
+            Escaped : readTemplate' (drop 2 string)
         | "$" `isPrefixOf` string =
-            let (key, rest) = readIdentifier $ drop 1 string
-            in Identifier key : readTemplate' rest
+            case readIdentifier (drop 1 string) of
+                Just (key, rest) -> Identifier key : readTemplate' rest
+                Nothing          -> Chunk "$" : readTemplate' (drop 1 string)
         | otherwise =
             let (chunk, rest) = break (== '$') string
             in Chunk chunk : readTemplate' rest
 
-    -- Parse an identifier into (identifier, rest)
-    readIdentifier = span isAlphaNum
+    -- Parse an identifier into (identifier, rest) if it's valid, and return
+    -- Nothing otherwise
+    readIdentifier string =
+        let (identifier, rest) = span isAlphaNum string
+        in if not (null identifier) && "$" `isPrefixOf` rest
+            then Just (identifier, drop 1 rest)
+            else Nothing
 
 -- | Substitutes @$identifiers@ in the given @Template@ by values from the given
 --   "Page". When a key is not found, it is left as it is. You can specify
@@ -44,7 +49,7 @@ applyTemplate template page =
     substitute (Chunk chunk) = chunk
     substitute (Identifier key) =
         fromMaybe ('$' : key) $ M.lookup key $ toMap page
-    substitute (Escaped key) = '$' : key
+    substitute (Escaped) = "$"
 
 -- | Apply a page as it's own template. This is often very useful to fill in
 -- certain keys like @$root@ and @$url@.
diff --git a/src/Hakyll/Web/Template/Internal.hs b/src/Hakyll/Web/Template/Internal.hs
index 096c928..d0f6472 100644
--- a/src/Hakyll/Web/Template/Internal.hs
+++ b/src/Hakyll/Web/Template/Internal.hs
@@ -29,17 +29,17 @@ instance Writable Template where
 data TemplateElement
     = Chunk String
     | Identifier String
-    | Escaped String
+    | Escaped
     deriving (Show, Eq, Typeable)
 
 instance Binary TemplateElement where
     put (Chunk string)    = putWord8 0 >> put string
     put (Identifier key)  = putWord8 1 >> put key
-    put (Escaped key) = putWord8 2 >> put key
+    put (Escaped) = putWord8 2
 
     get = getWord8 >>= \tag -> case tag of
             0 -> Chunk      <$> get
             1 -> Identifier <$> get
-            2 -> Escaped    <$> get
+            2 -> return Escaped
             _ -> error $  "Hakyll.Web.Template.Internal: "
                        ++ "Error reading cached template"
-- 
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