Update OpApp layouting options

- Allow par-spacing for single-operator 1+n-line layout
- Tweak when to flatten operators, i.e. when to allow a flat one-line-each
  layout for the operator sequence "$ $ $ + +".

data/10-structured/expression-special.blt

@@ -2,11 +2,8 @@
 
 
 #test monad-comprehension-case-of
-func =
+func = foooooo
-  foooooo
+  $ [ case foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo of
-    $ [ case
-          foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
-        of
         _ -> True
     ]
 

data/10-structured/op-precedence.blt

@@ -164,14 +164,16 @@ doop =
 #expected
 -- brittany { lconfig_fixityBasedAddAlignParens: True }
 doop =
-  (  some long invocation == loooooooooongman + (third nested expression) - 4
+  (  (  some long invocation == loooooooooongman + (third nested expression) - 4
      && {- meow -} 5 - 6 > 7 `mod` loooooooooongwoman
+     )
   || ill just invoke a function with these args
   || (  foo
-     && dooasdoiaosdoi ** oaisdoioasido
+     && (  dooasdoiaosdoi ** oaisdoioasido
         <= asduiuaisduiasdu + asdahjsd + ahsjdhjhasd
         )
      )
+  )
 
 #golden multiline mixed op expression 1
 -- brittany { lconfig_fixityBasedAddAlignParens: True }

data/15-regressions.blt

@@ -319,8 +319,7 @@ parserCompactLocation =
   ]
 
 #test opapp-specialcasing-1
-func =
+func = fooooooooooooooooooooooooooooooooo
-  fooooooooooooooooooooooooooooooooo
   $ foooooooooooooooooooooooooooooooo foooooooooooooooooooooooooooooooo
                                       foooooooooooooooooooooooooooooooo
 

source/library/Language/Haskell/Brittany/Internal/ToBriDoc/OpTree.hs

@@ -222,6 +222,7 @@ layoutOpTree allowSinglelinePar = \case
     -> ToBriDocM BriDocNumbered
   coreAlternative hasParen locO locC fixity docL sharedOps sharedOpsFlat lastWrap
     = do
+      indentPolicy <- askLayoutConf _lconfig_indentPolicy
       let wrapParenIfSl x inner = if x then wrapParenSl inner else docSetParSpacing inner
           wrapParenSl inner = docAlt
             [ docSeq
@@ -253,6 +254,8 @@ layoutOpTree allowSinglelinePar = \case
             Nothing                -> False
             Just (Fixity _ prec _) -> prec > 0
 
+      let isSingleOp = length sharedOps == 1 && length sharedOpsFlat == 1
+
       runFilteredAlternative $ do
         -- > one + two + three
         -- or
@@ -262,7 +265,7 @@ layoutOpTree allowSinglelinePar = \case
           $ wrapParenIfSl hasParen
           $ docSetParSpacing
           $ docSeq
-          ([docForceSingleline docL] ++ case splitFirstLast sharedOps of
+          ([docForceSingleline docL] ++ case splitFirstLast sharedOpsFlat of
             FirstLastEmpty -> []
             FirstLastSingleton (od, ed) ->
               [docSeparator, docForceSingleline od, docSeparator, lastWrap ed]
@@ -289,11 +292,29 @@ layoutOpTree allowSinglelinePar = \case
           )
         -- this case rather leads to some unfortunate layouting than to anything
         -- useful; disabling for now. (it interfers with cols stuff.)
-        addAlternativeCond (not hasParen) $ docPar
+        -- one
+        -- + two
+        -- + three
+        addAlternativeCond (not hasParen && not isSingleOp) $ docPar
           (docHandleComms locO $ docForceSingleline $ docL)
           (docFlushCommsPost False locC $ docLines $ sharedOps <&> \(od, ed) ->
             docCols ColOpPrefix [appSep od, docForceSingleline ed]
           )
+        let singlelineUnlessFree = case indentPolicy of
+              IndentPolicyLeft     -> docForceSingleline
+              IndentPolicyMultiple -> docForceSingleline
+              IndentPolicyFree     -> id
+        let curIsPrec0 = case fixity of
+              Nothing -> False
+              Just (Fixity _ prec _) -> prec == 0
+        case sharedOps of
+          [(od, ed)] | curIsPrec0 ->
+            addAlternativeCond (not hasParen && isSingleOp)
+              $ docSetParSpacing
+              $ docPar
+                (docHandleComms locO $ docForceSingleline $ docL)
+                (docSeq [od, docSeparator, singlelineUnlessFree ed])
+          _ -> pure ()
         -- > ( one
         -- > + two
         -- > + three