Extend single-line list formatting beyond function arguments

Previously, single-line list formatting was limited to lists within function arguments. This change extends the behavior to all lists, applying the same rules:
- Lists with >6 items always: expand
- Lists with >1 items and at least one non-simple item: expand
- Otherwise: try to fit on one line

Author: dyegoaurelio

src/Nixfmt/Pretty.hs

@@ -110,8 +110,8 @@ instance (Pretty a) => Pretty (Item a) where
   pretty (Item x) = group x
 
 -- For lists, attribute sets and let bindings
-prettyItems :: (Pretty a) => Items a -> Doc
-prettyItems (Items items) = go items
+prettyItemsWith :: (Pretty a) => Doc -> Items a -> Doc
+prettyItemsWith separator (Items items) = go items
   where
     go [] = mempty
     go [item] = pretty item
@@ -120,9 +120,9 @@ prettyItems (Items items) = go items
       pretty (LanguageAnnotation lang)
         <> hardspace
         <> group stringItem
-        <> if null rest then mempty else hardline <> go rest
+        <> if null rest then mempty else separator <> go rest
     go (item : rest) =
-      pretty item <> if null rest then mempty else hardline <> go rest
+      pretty item <> if null rest then mempty else separator <> go rest
 
 instance Pretty Trivia where
   pretty [] = mempty
@@ -197,7 +197,7 @@ prettySet _ (krec, paropen@(LoneAnn _), Items [], parclose@Ann{preTrivia = []})
 -- Singleton sets are allowed to fit onto one line,
 -- but apart from that always expand.
 prettySet wide (krec, paropen@Ann{trailComment = post}, binders, parclose) =
-  let !surrounded = surroundWith sep (nest $ pretty post <> prettyItems binders)
+  let !surrounded = surroundWith sep (nest $ pretty post <> prettyItemsWith hardline binders)
   in pretty (fmap (,hardspace) krec)
       <> pretty (paropen{trailComment = Nothing})
       <> surrounded
@@ -242,14 +242,16 @@ prettyTerm (List paropen@Ann{trailComment = Nothing} (Items []) parclose@Ann{pre
     -- If the brackets are on different lines, keep them like that
     sep = if sourceLine paropen /= sourceLine parclose then hardline else hardspace
 -- General list
--- Always expand if len > 1
 prettyTerm (List paropen@Ann{trailComment = post} items parclose) =
   pretty (paropen{trailComment = Nothing})
-    <> surroundWith sur (nest $ pretty post <> prettyItems items)
+    <> surroundWith sur (nest $ pretty post <> prettyItemsWith sur items)
     <> pretty parclose
   where
-    -- If the brackets are on different lines, keep them like that
-    sur = if sourceLine paropen /= sourceLine parclose then hardline else line
+    sur
+      | sourceLine paropen /= sourceLine parclose = hardline -- If the brackets are on different lines, keep them like that
+      | length (unItems items) > 6 = hardline -- More than 6 items: always expand
+      | length (unItems items) > 1 && not (all (isSimple . Term) items) = hardline -- More than 1 item containing non-simple items: expand
+      | otherwise = line -- Otherwise, try to fit onto one line
 prettyTerm (Set krec paropen items parclose) = prettySet False (krec, paropen, items, parclose)
 -- Parentheses
 prettyTerm (Parenthesized paropen expr parclose@Ann{preTrivia = closePre}) =
@@ -412,36 +414,19 @@ prettyApp indentFunction pre hasPost f a =
       -- This is very hacky, but selections shouldn't be in a priority group,
       -- because if they get expanded before anything else,
       -- only the `.`-and-after part gets to a new line, which looks very odd
-      absorbApp (Application f' a'@(Term Selection{})) = group' Transparent (absorbApp f') <> line <> nest (group' RegularG $ absorbInner a')
+      absorbApp (Application f' a'@(Term Selection{})) = group' Transparent (absorbApp f') <> line <> nest (group' RegularG $ pretty a')
       -- If two consecutive arguments are lists, treat them specially: Don't priority expand, and also
       -- if one does not fit onto the line then put both on a new line each.
       -- Note that this does not handle the case where the two last arguments are lists, as the last argument
       -- is handled elsewhere and cannot be pattern-matched here.
       absorbApp (Application (Application f' l1@(Term List{})) l2@(Term List{})) =
-        group' Transparent (group' Transparent (absorbApp f') <> nest (group' RegularG $ line <> group (absorbInner l1) <> line <> group (absorbInner l2)))
-      absorbApp (Application f' a') = group' Transparent (absorbApp f') <> line <> nest (group' Priority $ absorbInner a')
+        group' Transparent (group' Transparent (absorbApp f') <> nest (group' RegularG $ line <> group (pretty l1) <> line <> group (pretty l2)))
+      absorbApp (Application f' a') = group' Transparent (absorbApp f') <> line <> nest (group' Priority $ pretty a')
       -- First argument
       absorbApp expr
         | indentFunction && null comment' = nest $ group' RegularG $ line' <> pretty expr
         | otherwise = pretty expr
 
-      -- Render the inner arguments of a function call
-      absorbInner :: Expression -> Doc
-      -- If lists have only simple items, try to render them single-line instead of expanding
-      -- This is just a copy of the list rendering code, but with `sepBy line` instead of `sepBy hardline`
-      absorbInner (Term (List paropen@Ann{trailComment = post'} items parclose))
-        | length (unItems items) <= 6 && all (isSimple . Term) items =
-            pretty (paropen{trailComment = Nothing})
-              <> surroundWith sur (nest $ pretty post' <> sepBy line (unItems items))
-              <> pretty parclose
-        where
-          -- If the brackets are on different lines, keep them like that
-          sur
-            | sourceLine paropen /= sourceLine parclose = hardline
-            | null $ unItems items = hardspace
-            | otherwise = line
-      absorbInner expr = pretty expr
-
       -- Render the last argument of a function call
       absorbLast :: Expression -> Doc
       absorbLast (Term t)
@@ -512,9 +497,9 @@ prettyApp indentFunction pre hasPost f a =
           group' RegularG $
             (pre <> group' Transparent (absorbApp fWithoutCommandAndWithoutArg))
               <> line
-              <> nest (group (absorbInner l1))
+              <> nest (group (pretty l1))
               <> line
-              <> nest (group (absorbInner l2))
+              <> nest (group (pretty l2))
               <> post
         _ ->
           renderSimple
@@ -696,7 +681,7 @@ instance Pretty Expression where
       convertTrailing (Just (TrailingComment t)) = [LineComment (" " <> t)]
 
       letPart = group $ pretty let_ <> hardline <> letBody
-      letBody = nest $ prettyItems binders
+      letBody = nest $ prettyItemsWith hardline binders
       inPart =
         group $
           pretty in_

test/correct-indent-4.nix

@@ -466,12 +466,7 @@ rec {
         }:
         assert isInt depthLimit;
         let
-            specialAttrs = [
-                "__functor"
-                "__functionArgs"
-                "__toString"
-                "__pretty"
-            ];
+            specialAttrs = [ "__functor" "__functionArgs" "__toString" "__pretty" ];
             stepIntoAttr = evalNext: name: if elem name specialAttrs then id else evalNext;
             transform =
                 depth:
@@ -543,11 +538,7 @@ rec {
                 else if isString v then
                     let
                         lines = filter (v: !isList v) (split "\n" v);
-                        escapeSingleline = escape [
-                            "\\"
-                            "\""
-                            "\${"
-                        ];
+                        escapeSingleline = escape [ "\\" "\"" "\${" ];
                         escapeMultiline = replaceStrings [ "\${" "''" ] [ "''\${" "'''" ];
                         singlelineResult =
                             "\"" + concatStringsSep "\\n" (map escapeSingleline lines) + "\"";

test/diff/apply/out-pure.nix

@@ -155,11 +155,7 @@
       utils.lib.eachDefaultSystem (system: { });
   }
   {
-    escapeSingleline = libStr.escape [
-      "\\"
-      ''"''
-      "\${"
-    ];
+    escapeSingleline = libStr.escape [ "\\" ''"'' "\${" ];
     escapeMultiline = libStr.replaceStrings [ "\${" "''" ] [ "''\${" "'''" ];
     test =
       foo

test/diff/apply_with_lists/out-pure.nix

@@ -2,10 +2,7 @@
 
 [
   (f [ ] [ rhs lhs ])
-  (lib.mkMerge [
-    false
-    false
-  ])
+  (lib.mkMerge [ false false ])
   (replaceStrings
     [ "\${" "''" ]
     #force multiline
@@ -46,30 +43,12 @@
     [ "services" "xserver" "displayManager" "sddm" "enable" ]
     [ "services" "displayManager" "sddm" "enable" ]
   )
-  (map (
-    buildAllowCommand "allow" [
-      "snapshot"
-      "mount"
-      "destroy"
-    ]
-  ))
-  (map
-    (
-      x:
-      "${x} ${
-        escapeShellArgs [
-          stateDir
-          workDir
-          logsDir
-        ]
-      }"
-    )
-    [
-      "+${unconfigureRunner}" # runs as root
-      configureRunner
-      setupWorkDir
-    ]
-  )
+  (map (buildAllowCommand "allow" [ "snapshot" "mount" "destroy" ]))
+  (map (x: "${x} ${escapeShellArgs [ stateDir workDir logsDir ]}") [
+    "+${unconfigureRunner}" # runs as root
+    configureRunner
+    setupWorkDir
+  ])
   (lib.checkListOfEnum "${pname}: theme accent"
     [ "Blue" "Flamingo" "Green" ]
     [ accent ]
@@ -82,17 +61,11 @@
     [ coq.coq-version ssreflect.version ]
     [
       {
-        cases = [
-          (lib.versions.range "8.15" "8.20")
-          lib.pred.true
-        ];
+        cases = [ (lib.versions.range "8.15" "8.20") lib.pred.true ];
         out = "2.0.4";
       }
       {
-        cases = [
-          "8.5"
-          lib.pred.true
-        ];
+        cases = [ "8.5" lib.pred.true ];
         out = "20170512";
       }
     ]

test/diff/apply_with_lists/out.nix

@@ -2,10 +2,7 @@
 
 [
   (f [ ] [ rhs lhs ])
-  (lib.mkMerge [
-    false
-    false
-  ])
+  (lib.mkMerge [ false false ])
   (replaceStrings
     [ "\${" "''" ]
     #force multiline
@@ -52,30 +49,12 @@
     ]
     [ "services" "displayManager" "sddm" "enable" ]
   )
-  (map (
-    buildAllowCommand "allow" [
-      "snapshot"
-      "mount"
-      "destroy"
-    ]
-  ))
-  (map
-    (
-      x:
-      "${x} ${
-        escapeShellArgs [
-          stateDir
-          workDir
-          logsDir
-        ]
-      }"
-    )
-    [
-      "+${unconfigureRunner}" # runs as root
-      configureRunner
-      setupWorkDir
-    ]
-  )
+  (map (buildAllowCommand "allow" [ "snapshot" "mount" "destroy" ]))
+  (map (x: "${x} ${escapeShellArgs [ stateDir workDir logsDir ]}") [
+    "+${unconfigureRunner}" # runs as root
+    configureRunner
+    setupWorkDir
+  ])
   (lib.checkListOfEnum "${pname}: theme accent"
     [
       "Blue"