Allow nice and fancy algorithms to add modules according to whether e…

…xisting modules in target field are separated by spaces instead of commas

Add tests which verify correct behaviour

cabal-add.cabal

@@ -89,8 +89,10 @@ test-suite cabal-add-tests
 
 test-suite cabal-add-unit-tests
   type:                 exitcode-stdio-1.0
-  hs-source-dirs:       tests/
   main-is:              UnitTests.hs
+  hs-source-dirs:       tests/
+  default-language:   GHC2021
+  ghc-options:        -Wall
   build-depends:
         base <5,
         bytestring,

src/Distribution/Client/Add.hs

@@ -409,11 +409,15 @@ isFieldWithName name = \case
   Field (Name _ fieldName) _ -> name == fieldName
   _ -> False
 
-detectLeadingComma :: ByteString -> Maybe ByteString
-detectLeadingComma xs = case B.uncons xs of
+detectLeadingSeparator :: ByteString -> Maybe ByteString
+detectLeadingSeparator xs = case B.uncons xs of
   Just (',', ys) -> Just $ B.cons ',' $ B.takeWhile (== ' ') ys
+  Just (' ', ys) -> Just $ B.takeWhile (== ' ') ys
   _ -> Nothing
 
+isCommaSeparated :: ByteString -> Bool
+isCommaSeparated xs = ',' `B.elem` xs
+
 dropRepeatingSpaces :: ByteString -> ByteString
 dropRepeatingSpaces xs = case B.uncons xs of
   Just (' ', ys) -> B.cons ' ' (B.dropWhile (== ' ') ys)
@@ -437,14 +441,14 @@ fancyAlgorithm Config {cnfFields, cnfComponent, cnfOrigContents, cnfAdditions, c
         _ -> Nothing
       fillerPred c = isSpaceChar8 c || c == ','
 
-  let (B.takeWhileEnd fillerPred -> pref, B.takeWhile fillerPred -> suff) =
-        splitAtPosition firstDepPos cnfOrigContents
+  let (rawPref, rawSuff) = splitAtPosition firstDepPos cnfOrigContents
+      (B.takeWhileEnd fillerPred -> pref, B.takeWhile fillerPred -> suff) = (rawPref, rawSuff)
       prefSuff = pref <> suff
-
+      noCommaSeparation = not (isCommaSeparated rawSuff) && (cnfTargetField /= BuildDepends)
       (afterLast, inBetween, beforeFirst) = case secondDepPos of
         Nothing ->
-          ( if B.any (== ',') prefSuff then pref' else "," <> pref'
-          , if B.any (== ',') prefSuff then prefSuff' else "," <> prefSuff'
+          ( if B.any (== ',') prefSuff || noCommaSeparation then pref' else "," <> pref'
+          , if B.any (== ',') prefSuff || noCommaSeparation then prefSuff' else "," <> prefSuff'
           , suff
           )
           where
@@ -478,13 +482,14 @@ niceAlgorithm Config {cnfFields, cnfComponent, cnfOrigContents, cnfAdditions, cn
 
   let (before, after) = splitAtPosition pos cnfOrigContents
       (_, targetHeader) = splitAtPosition (getFieldNameAnn targetField) before
+      leadingSeparatorStyle = detectLeadingSeparator after
       filler = dropRepeatingSpaces $ B.drop 1 $ B.dropWhile (/= ':') targetHeader
-      leadingCommaStyle = detectLeadingComma after
-      filler' = maybe ("," <> filler) (filler <>) leadingCommaStyle
+      defaultSep = if isCommaSeparated after || cnfTargetField == BuildDepends then "," else ""
+      filler' = maybe (defaultSep <> filler) (filler <>) leadingSeparatorStyle
       newFieldContents =
-        fromMaybe "" leadingCommaStyle
+        fromMaybe "" leadingSeparatorStyle
           <> B.intercalate filler' (NE.toList cnfAdditions)
-          <> (if isJust leadingCommaStyle then filler else filler')
+          <> (if isJust leadingSeparatorStyle then filler else filler')
   pure $
     before <> newFieldContents <> after