From 3c15d0fd34e6fd8b2a2c2c9185f5554fc266efbc Mon Sep 17 00:00:00 2001
From: Jasper Van der Jeugt <m@jaspervdj.be>
Date: Tue, 28 Oct 2014 10:53:35 +0100
Subject: Improve rulesExtraDependencies usage

---
 src/Hakyll/Core/Rules.hs | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

(limited to 'src')

diff --git a/src/Hakyll/Core/Rules.hs b/src/Hakyll/Core/Rules.hs
index c248a9b..1b1e4ae 100644
--- a/src/Hakyll/Core/Rules.hs
+++ b/src/Hakyll/Core/Rules.hs
@@ -181,10 +181,32 @@ preprocess = Rules . liftIO
 --
 -- A useful utility for this purpose is 'makePatternDependency'.
 rulesExtraDependencies :: [Dependency] -> Rules a -> Rules a
-rulesExtraDependencies deps = Rules . censor addDependencies . unRules
+rulesExtraDependencies deps rules =
+    -- Note that we add the dependencies seemingly twice here. However, this is
+    -- done so that 'rulesExtraDependencies' works both if we have something
+    -- like:
+    --
+    -- > match "*.css" $ rulesExtraDependencies [foo] $ ...
+    --
+    -- and something like:
+    --
+    -- > rulesExtraDependencies [foo] $ match "*.css" $ ...
+    --
+    -- (1) takes care of the latter and (2) of the former.
+    Rules $ censor fixRuleSet $ do
+        x <- unRules rules
+        fixCompiler
+        return x
   where
-    -- Adds the dependencies to the compilers in the ruleset
-    addDependencies ruleSet = ruleSet
+    -- (1) Adds the dependencies to the compilers we are yet to create
+    fixCompiler = modify $ \s -> case rulesCompiler s of
+        Nothing -> s
+        Just c  -> s
+            { rulesCompiler = Just $ compilerTellDependencies deps >> c
+            }
+
+    -- (2) Adds the dependencies to the compilers that are already in the ruleset
+    fixRuleSet ruleSet = ruleSet
         { rulesCompilers =
             [ (i, compilerTellDependencies deps >> c)
             | (i, c) <- rulesCompilers ruleSet
-- 
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