From 12a8058284853b743fd2d289f2a05a44c1675baf Mon Sep 17 00:00:00 2001
From: Adrian Cochrane <adrian@openwork.nz>
Date: Fri, 8 May 2020 20:17:03 +1200
Subject: [PATCH] Expand :is/:where lowering.

---
 src/Data/CSS/Style/Selector/LowerWhere.hs | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/src/Data/CSS/Style/Selector/LowerWhere.hs b/src/Data/CSS/Style/Selector/LowerWhere.hs
index fc3e024..5fb0882 100644
--- a/src/Data/CSS/Style/Selector/LowerWhere.hs
+++ b/src/Data/CSS/Style/Selector/LowerWhere.hs
@@ -6,12 +6,14 @@ module Data.CSS.Style.Selector.LowerWhere(
 import Data.CSS.Syntax.Selector
 import Data.CSS.Style.Common
 
-lowerSelector :: Selector -> Selector
-lowerSelector (Element sel) = Element $ lowerSelector' sel
-lowerSelector (Child sel x) = Child (lowerSelector sel) x
-lowerSelector (Descendant sel x) = Descendant (lowerSelector sel) x
-lowerSelector (Adjacent sel x) = Adjacent (lowerSelector sel) x
-lowerSelector (Sibling sel x) = Sibling (lowerSelector sel) x
+lowerSelector :: Selector -> [Selector]
+lowerSelector (Element [Psuedoclass c args])
+    | c `elem` ["is", "where"], (args', []) <- parseSelectors args = args'
+lowerSelector (Element sel) = [Element $ lowerSelector' sel]
+lowerSelector (Child sel x) = [Child sel' $ lowerSelector' x | sel' <- lowerSelector sel]
+lowerSelector (Descendant sel x) = [Descendant sel' $ lowerSelector' x | sel' <- lowerSelector sel]
+lowerSelector (Adjacent sel x) = [Adjacent sel' $ lowerSelector' x | sel' <- lowerSelector sel]
+lowerSelector (Sibling sel x) = [Sibling sel' $ lowerSelector' x | sel' <- lowerSelector sel]
 
 lowerSelector' :: [SimpleSelector] -> [SimpleSelector]
 lowerSelector' (Psuedoclass c args:sel)
@@ -25,8 +27,10 @@ data WhereLowerer s = WhereLowerer s
 instance RuleStore s => RuleStore (WhereLowerer s) where
     new = WhereLowerer new
     addStyleRule (WhereLowerer self) priority rule =
-        WhereLowerer $ addStyleRule self priority $ rule {
-            inner = StyleRule (lowerSelector sel) props psuedo
+        WhereLowerer $ foldl addStyleRule' self $ lowerSelector sel
+      where
+        addStyleRule' self' sel' = addStyleRule self' priority $ rule {
+            inner = StyleRule sel' props psuedo
         }
-      where StyleRule sel props psuedo = inner rule
+        StyleRule sel props psuedo = inner rule
     lookupRules (WhereLowerer self) el = lookupRules self el
-- 
2.30.2