Improve layouting of RecordUpd, Fix minor issue for HsLet

src-literatetests/15-regressions.blt

@@ -367,9 +367,8 @@ runBrittany tabSize text = do
   let
     config' = staticDefaultConfig
     config  = config'
-      { _conf_layout  = (_conf_layout config') { _lconfig_indentAmount = coerce
+      { _conf_layout  =
-                                                 tabSize
+        (_conf_layout config') { _lconfig_indentAmount = coerce tabSize }
-                                               }
       , _conf_forward = forwardOptionsSyntaxExtsEnabled
       }
   parsePrintModule config text

src/Language/Haskell/Brittany/Internal/Layouters/Expr.hs

@@ -535,13 +535,15 @@ layoutExpr lexpr@(L _ expr) = do
         ifIndentLeftElse :: a -> a -> a
         ifIndentLeftElse x y =
           if indentPolicy == IndentPolicyLeft then x else y
-      -- this `docSetIndentLevel` might seem out of place, but is here due to
+      -- this `docSetBaseAndIndent` might seem out of place (especially the
-      -- ghc-exactprint's DP handling of "let" in particular.
+      -- Indent part; setBase is necessary due to the use of docLines below),
+      -- but is here due to ghc-exactprint's DP handling of "let" in
+      -- particular.
       -- Just pushing another indentation level is a straightforward approach
       -- to making brittany idempotent, even though the result is non-optimal
       -- if "let" is moved horizontally as part of the transformation, as the
       -- comments before the first let item are moved horizontally with it.
-      docSetIndentLevel $ case mBindDocs of
+      docSetBaseAndIndent $ case mBindDocs of
         Just [bindDoc] -> docAlt
           [ docSeq
               [ appSep $ docLit $ Text.pack "let"
@@ -733,6 +735,8 @@ layoutExpr lexpr@(L _ expr) = do
         , docLit $ Text.pack "}"
         ]
     RecordCon lname _ _ (HsRecFields fs@(_:_) Nothing) -> do
+      -- TODO: the layouter for RecordUpd is slightly more clever. Should
+      -- probably copy the approach from there.
       let nameDoc = docWrapNode lname $ docLit $ lrdrNameToText lname
       ((fd1l, fd1n, fd1e):fdr) <- fs `forM` \fieldl@(L _ (HsRecField (L _ (FieldOcc lnameF _)) fExpr pun)) -> do
         fExpDoc <- if pun
@@ -852,7 +856,7 @@ layoutExpr lexpr@(L _ expr) = do
             Unambiguous n _ -> (lfield, lrdrNameToText n, rFExpDoc)
             Ambiguous   n _ -> (lfield, lrdrNameToText n, rFExpDoc)
       docAltFilter
-        -- singleline
+        -- container { fieldA = blub, fieldB = blub }
         [ ( True
           , docSeq
             [ docNodeAnnKW lexpr Nothing $ appSep $ docForceSingleline rExprDoc
@@ -870,7 +874,10 @@ layoutExpr lexpr@(L _ expr) = do
             , docLit $ Text.pack "}"
             ]
           )
-        -- wild-indentation block
+        -- hanging single-line fields
+        -- container { fieldA = blub
+        --           , fieldB = blub
+        --           }
         , ( indentPolicy /= IndentPolicyLeft
           , docSeq
             [ docNodeAnnKW lexpr Nothing $ appSep rExprDoc
@@ -881,7 +888,7 @@ layoutExpr lexpr@(L _ expr) = do
                   , case rF1e of
                       Just x -> docWrapNodeRest rF1f $ docSeq
                                       [ appSep $ docLit $ Text.pack "="
-                                      , docForceSingleline $ x
+                                      , docForceSingleline x
                                       ]
                       Nothing -> docEmpty
                   ]
@@ -901,28 +908,45 @@ layoutExpr lexpr@(L _ expr) = do
                 in [line1] ++ lineR ++ [lineN]
             ]
           )
-        -- strict indentation block
+          -- non-hanging with expressions placed to the right of the names
+          -- container
+          -- { fieldA = blub
+          -- , fieldB = potentially
+          --     multiline
+          -- }
         , ( True
           , docSetParSpacing
           $ docAddBaseY BrIndentRegular
           $ docPar
               (docNodeAnnKW lexpr Nothing $ rExprDoc)
               (docNonBottomSpacing $ docLines $ let
+                expressionWrapper = if indentPolicy == IndentPolicyLeft
+                  then docForceParSpacing
+                  else docSetBaseY
                 line1 = docCols ColRecUpdate
                   [ appSep $ docLit $ Text.pack "{"
                   , docWrapNodePrior rF1f $ appSep $ docLit $ rF1n
                   , docWrapNodeRest rF1f $ case rF1e of
-                      Just x -> docSeq [ appSep $ docLit $ Text.pack "="
+                      Just x -> docAlt
-                                      , docAddBaseY BrIndentRegular $ x
+                        [ docSeq [ appSep $ docLit $ Text.pack "="
+                                 , expressionWrapper x
+                                 ]
+                        , docAddBaseY BrIndentRegular
+                        $ docPar (docLit $ Text.pack "=") x
                         ]
                       Nothing -> docEmpty
                   ]
-                lineR = rFr <&> \(lfield, fText, fDoc) -> docWrapNode lfield $ docCols ColRecUpdate
+                lineR = rFr <&> \(lfield, fText, fDoc) -> docWrapNode lfield
+                  $ docCols ColRecUpdate
                   [ docCommaSep
                   , appSep $ docLit $ fText
                   , case fDoc of
-                      Just x ->  docSeq [ appSep $ docLit $ Text.pack "="
+                      Just x -> docAlt
-                                        , docAddBaseY BrIndentRegular x
+                        [ docSeq [ appSep $ docLit $ Text.pack "="
+                                 , expressionWrapper x
+                                 ]
+                        , docAddBaseY BrIndentRegular
+                        $ docPar (docLit $ Text.pack "=") x
                         ]
                       Nothing -> docEmpty
                   ]
@@ -930,7 +954,8 @@ layoutExpr lexpr@(L _ expr) = do
                   [ docNodeAnnKW lexpr (Just AnnOpenC) docEmpty
                   , docLit $ Text.pack "}"
                   ]
-                in [line1] ++ lineR ++ [lineN])
+                in [line1] ++ lineR ++ [lineN]
+              )
           )
         ]
 #if MIN_VERSION_ghc(8,2,0) /* ghc-8.2 */