From 9867094bd27ed170315e7e02b788243d654c6bc1 Mon Sep 17 00:00:00 2001
From: samgd <sam@samgd.com>
Date: Sat, 23 Jul 2016 14:46:15 +0200
Subject: Expr trimming. '-' binds to '$'.

---
 src/Hakyll/Core/Util/Parser.hs      | 11 +++++++++--
 src/Hakyll/Web/Template/Internal.hs | 13 ++++++++-----
 tests/Hakyll/Web/Template/Tests.hs  |  7 +++++++
 3 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/src/Hakyll/Core/Util/Parser.hs b/src/Hakyll/Core/Util/Parser.hs
index e958b76..c4b2f8d 100644
--- a/src/Hakyll/Core/Util/Parser.hs
+++ b/src/Hakyll/Core/Util/Parser.hs
@@ -8,7 +8,7 @@ module Hakyll.Core.Util.Parser
 
 --------------------------------------------------------------------------------
 import           Control.Applicative ((<|>))
-import           Control.Monad       (mzero)
+import           Control.Monad       (guard, mzero, void)
 import qualified Text.Parsec         as P
 import           Text.Parsec.String  (Parser)
 
@@ -16,7 +16,14 @@ import           Text.Parsec.String  (Parser)
 --------------------------------------------------------------------------------
 metadataKey :: Parser String
 metadataKey = do
-    i <- (:) <$> P.letter <*> (P.many $ P.alphaNum <|> P.oneOf "_-.")
+    -- Ensure trailing '-' binds to '$' if present.
+    let hyphon = P.try $ do
+            void $ P.char '-'
+            x <- P.lookAhead P.anyChar
+            guard $ x /= '$'
+            pure '-'
+
+    i <- (:) <$> P.letter <*> P.many (P.alphaNum <|> P.oneOf "_." <|> hyphon)
     if i `elem` reservedKeys then mzero else return i
 
 
diff --git a/src/Hakyll/Web/Template/Internal.hs b/src/Hakyll/Web/Template/Internal.hs
index 6ccad74..fce163f 100644
--- a/src/Hakyll/Web/Template/Internal.hs
+++ b/src/Hakyll/Web/Template/Internal.hs
@@ -143,7 +143,7 @@ template = mconcat <$> P.many (P.choice [ lift chunk
                                         , conditional
                                         , for
                                         , partial
-                                        , lift expr
+                                        , expr
                                         ])
     where lift = fmap (Template . (:[]))
 
@@ -154,12 +154,15 @@ chunk = Chunk <$> P.many1 (P.noneOf "$")
 
 
 --------------------------------------------------------------------------------
-expr :: P.Parser TemplateElement
+expr :: P.Parser Template
 expr = P.try $ do
-    void $ P.char '$'
+    trimLExpr <- trimOpen
     e <- expr'
-    void $ P.char '$'
-    return $ Expr e
+    trimRExpr <- trimClose
+    return $ Template $ mconcat [ [TrimL | trimLExpr]
+                                , [Expr e]
+                                , [TrimR | trimRExpr]
+                                ]
 
 
 --------------------------------------------------------------------------------
diff --git a/tests/Hakyll/Web/Template/Tests.hs b/tests/Hakyll/Web/Template/Tests.hs
index 1ace2d4..a7b31a7 100644
--- a/tests/Hakyll/Web/Template/Tests.hs
+++ b/tests/Hakyll/Web/Template/Tests.hs
@@ -75,6 +75,13 @@ tests = testGroup "Hakyll.Core.Template.Tests" $ concat
             , TrimR
             ]
             @=? readTemplate "$-partial(\"path\")-$"
+        -- 'Expr' trim check.
+        , Template
+            [ TrimL
+            , Expr (Ident (TemplateKey "foo"))
+            , TrimR
+            ]
+            @=? readTemplate "$-foo-$"
         ]
     ]
 
-- 
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