fix: csv: fix regression in parsing rules containing & (#2352)

hledger-lib/Hledger/Read/RulesReader.hs

@@ -723,7 +723,7 @@ regexp end = do
        Left x -> Fail.fail $ "CSV parser: " ++ x
        Right x -> return x
   where
-    double_ampersand = lookAhead . void $ char '&' >> char '&'
+    double_ampersand = lookAhead . void $ string "&&"
 
 -- -- A match operator, indicating the type of match to perform.
 -- -- Currently just ~ meaning case insensitive infix regex match.
@@ -1596,9 +1596,14 @@ tests_RulesReader = testGroup "RulesReader" [
    --    parseWithState' defrules matcherp "%description ~ A A\n" @?= (Right $ FieldMatcher "%description" "A A")
    ]
 
+
   ,testGroup "regexp" [
     testCase "regexp.ends-before-&&" $
-      parseWithState' defrules (regexp empty) "A A && xxx" @?= (Right $ toRegexCI' "A A")
+      parseWithState' defrules (regexp eof) "A A && xxx" @?= (Right $ toRegexCI' "A A")
+   ,testCase "regexp contains &" $
+      parseWithState' defrules (regexp eof) "A & B" @?= (Right $ toRegexCI' "A & B")
+   ,testCase "regexp contains escaped &" $
+      parseWithState' defrules (regexp eof) "A \\& B" @?= (Right $ toRegexCI' "A \\& B")
    ]
 
   , let matchers = [RecordMatcher Or (toRegexCI' "A"), RecordMatcher And (toRegexCI' "B")]

hledger/test/csv.test

@@ -1203,6 +1203,33 @@ $  ./csvtest.sh
 
 >=0
 
+# ** 62. Matchers can contain '&', either escaped or unescaped  (#2352)
+<
+2025-01-01,STOP & SHOP,100
+2025-01-01,H & M,100
+
+RULES
+fields date,description,amount
+
+if
+%description STOP & SHOP
+    account1 expenses:food
+
+if
+%description H \& M
+    account1 expenses:clothing
+
+$  ./csvtest.sh
+2025-01-01 STOP & SHOP
+    expenses:food              100
+    income:unknown            -100
+
+2025-01-01 H & M
+    expenses:clothing             100
+    income:unknown               -100
+
+>=
+
 # ** .
 #<
 #$  ./csvtest.sh