Expand attrset function parameters less

Keep up to two arguments compact, which benefits a lot of small functions
operating on key-value pairs.

src/Nixfmt/Pretty.hs

@@ -262,41 +262,46 @@ instance Pretty Term where
     pretty l@List{} = group $ prettyTerm l
     pretty x        = prettyTerm x
 
+-- Does not move around comments, nor does it inject a trailing comma
 instance Pretty ParamAttr where
-    -- Simple parameter, move comment around
-    -- Move comments around when switching from leading comma to trailing comma style:
-    -- `, name # foo` → `name, #foo`
-    pretty (ParamAttr (Ann trivia name (Just comment')) Nothing (Just (Ann trivia' comma Nothing)))
-            = pretty (ParamAttr (Ann trivia name Nothing) Nothing (Just (Ann trivia' comma (Just comment'))))
-
-    -- Simple parameter, move comment around and add trailing comma
-    -- Same as above, but also add trailing comma
-    pretty (ParamAttr (Ann trivia name (Just comment')) Nothing Nothing)
-            = pretty (ParamAttr (Ann trivia name Nothing) Nothing (Just (Ann [] TComma (Just comment'))))
-
-    -- Simple parameter
-    -- Still need to handle missing trailing comma here, because the special cases above are not exhaustive
+    -- Simple parameter (no default)
     pretty (ParamAttr name Nothing maybeComma)
-        = pretty name <> (fromMaybe (text ",") (fmap pretty maybeComma))
+        = pretty name <> pretty maybeComma
 
     -- With ? default
     pretty (ParamAttr name (Just (qmark, def)) maybeComma)
         = group (pretty name <> hardspace <> pretty qmark
             <> absorb softline mempty (Just 2) def)
-            <> (fromMaybe (text ",") (fmap pretty maybeComma))
+            <> pretty maybeComma
 
     -- `...`
     pretty (ParamEllipsis ellipsis)
         = pretty ellipsis
 
+-- Move comments around and inject trailing commas everywhere
+moveParamAttrComment :: ParamAttr -> ParamAttr
+-- Simple parameter, move comment around
+-- Move comments around when switching from leading comma to trailing comma style:
+-- `, name # foo` → `name, #foo`
+moveParamAttrComment (ParamAttr (Ann trivia name (Just comment')) Nothing (Just (Ann trivia' comma Nothing)))
+    = ParamAttr (Ann trivia name Nothing) Nothing (Just (Ann trivia' comma (Just comment')))
+-- Simple parameter, move comment around and add trailing comma
+-- Same as above, but also add trailing comma
+moveParamAttrComment (ParamAttr (Ann trivia name (Just comment')) Nothing Nothing)
+    = ParamAttr (Ann trivia name Nothing) Nothing (Just (Ann [] TComma (Just comment')))
+-- Other cases, just inject a trailing comma
+moveParamAttrComment (ParamAttr name def Nothing)
+    = ParamAttr name def (Just (Ann [] TComma Nothing))
+moveParamAttrComment x = x
+
 -- When a `, name` entry has some line comments before it, they are actually attached to the comment
 -- of the preceding item. Move them to the next one
-moveParamComments :: [ParamAttr] -> [ParamAttr]
-moveParamComments
+moveParamsComments :: [ParamAttr] -> [ParamAttr]
+moveParamsComments
     ((ParamAttr name maybeDefault (Just (Ann trivia comma Nothing))) : (ParamAttr (Ann [] name' Nothing) maybeDefault' maybeComma') : xs)
-    = (ParamAttr name maybeDefault (Just (Ann [] comma Nothing))) : moveParamComments ((ParamAttr (Ann trivia name' Nothing) maybeDefault' maybeComma') : xs)
-moveParamComments (x : xs) = x : moveParamComments xs
-moveParamComments [] = []
+    = (ParamAttr name maybeDefault (Just (Ann [] comma Nothing))) : moveParamsComments ((ParamAttr (Ann trivia name' Nothing) maybeDefault' maybeComma') : xs)
+moveParamsComments (x : xs) = x : moveParamsComments xs
+moveParamsComments [] = []
 
 instance Pretty Parameter where
     -- param:
@@ -307,10 +312,28 @@ instance Pretty Parameter where
         = group $ pretty bopen <> hardspace <> pretty bclose
 
     -- { stuff }:
-    pretty (SetParameter bopen attrs bclose)
-        = groupWithStart bopen $ hardline
-                  <> nest 2 (((sepBy hardline) . moveParamComments) attrs) <> hardline
-                  <> pretty bclose
+    pretty (SetParameter bopen attrs bclose) =
+        groupWithStart bopen $
+            (surroundWith sep $ nest 2 (sepBy sep $ handleTrailingComma $ map moveParamAttrComment $ moveParamsComments $ attrs))
+            <> pretty bclose
+        where
+        -- pretty all ParamAttrs, but make the trailing comma of the last element specially
+        handleTrailingComma :: [ParamAttr] -> [Doc]
+        handleTrailingComma [] = []
+        -- That's the case we're interested in
+        handleTrailingComma [(ParamAttr name maybeDefault (Just (Ann [] TComma Nothing)))]
+            = [pretty (ParamAttr name maybeDefault Nothing) <> trailing ","]
+        handleTrailingComma (x:xs) = pretty x : handleTrailingComma xs
+
+        sep = case attrs of
+            [] -> line
+            [ParamEllipsis _] -> line
+            -- Attributes must be without default
+            [ParamAttr _ Nothing _] -> line
+            [ParamAttr _ Nothing _, ParamEllipsis _] -> line
+            [ParamAttr _ Nothing _, ParamAttr _ Nothing _] -> line
+            [ParamAttr _ Nothing _, ParamAttr _ Nothing _, ParamEllipsis _] -> line
+            _ -> hardline
 
     pretty (ContextParameter param1 at param2)
         = pretty param1 <> pretty at <> pretty param2

test/diff/apply/out.nix

@@ -187,9 +187,7 @@
   # https://github.com/kamadorueda/alejandra/issues/372#issuecomment-1435083516
   {
     outputs =
-      {
-        utils,
-      }:
+      { utils }:
       # For each supported platform,
       utils.lib.eachDefaultSystem (system: { })
     ;

test/diff/idioms_lib_2/out.nix

@@ -1,6 +1,4 @@
-{
-  lib,
-}:
+{ lib }:
 
 rec {
 

test/diff/idioms_lib_3/out.nix

@@ -12,9 +12,7 @@
 #
 # Tests can be found in ./tests/misc.nix
 # Documentation in the manual, #sec-generators
-{
-  lib,
-}:
+{ lib }:
 with (lib).trivial;
 let
   libStr = lib.strings;
@@ -216,10 +214,7 @@ rec {
       # allow lists as values for duplicate keys
       listsAsDuplicateKeys ? false,
     }:
-    {
-      globalSection,
-      sections,
-    }:
+    { globalSection, sections }:
     (
       if globalSection == { } then
         ""

test/diff/idioms_lib_4/out.nix

@@ -14,9 +14,7 @@
 # e.g. exhaustive cases. Its more a sanity check to make sure nobody defines
 # systems that overlap with existing ones and won't notice something amiss.
 #
-{
-  lib,
-}:
+{ lib }:
 with lib.lists;
 with lib.types;
 with lib.attrsets;

test/diff/idioms_lib_5/out.nix

@@ -276,10 +276,7 @@ let
   ;
 
   handleEvalIssue =
-    {
-      meta,
-      attrs,
-    }:
+    { meta, attrs }:
     {
       reason,
       errormsg ? "",
@@ -303,10 +300,7 @@ let
   ;
 
   handleEvalWarning =
-    {
-      meta,
-      attrs,
-    }:
+    { meta, attrs }:
     {
       reason,
       errormsg ? "",
@@ -626,10 +620,7 @@ let
   ;
 
   assertValidity =
-    {
-      meta,
-      attrs,
-    }:
+    { meta, attrs }:
     let
       validity = checkValidity attrs;
     in

test/diff/idioms_nixos_2/out.nix

@@ -17,10 +17,7 @@ let
 
   phpPackage = cfg.phpPackage.buildEnv {
     extensions =
-      {
-        enabled,
-        all,
-      }:
+      { enabled, all }:
       (
         with all;
         # disable default openssl extension
@@ -995,13 +992,7 @@ in
               '';
               occInstallCmd =
                 let
-                  mkExport =
-                    {
-                      arg,
-                      value,
-                    }:
-                    "export ${arg}=${value}"
-                  ;
+                  mkExport = { arg, value }: "export ${arg}=${value}";
                   dbpass = {
                     arg = "DBPASS";
                     value =

test/diff/key_value/out.nix

@@ -56,13 +56,7 @@ rec {
       c = 2;
     };
   n = pkgs: { };
-  o =
-    {
-      pkgs,
-      ...
-    }:
-    { }
-  ;
+  o = { pkgs, ... }: { };
 
   a
     # b

test/diff/lambda/out.nix

@@ -45,43 +45,30 @@
   )
 
   (
-    {
-      pkgs,
-      ...
-    }:
+    { pkgs, ... }:
     {
       # Stuff
     }
   )
 
   (
-    {
-      pkgs,
-      ...
-    }:
+    { pkgs, ... }:
     let
     in
     pkgs
   )
 
   (
     a:
-    {
-      b,
-      ...
-    }:
+    { b, ... }:
     c: {
       # Stuff
     }
   )
 
   (
     a:
-    {
-      b,
-      c,
-      ...
-    }:
+    { b, c, ... }:
     d: {
       # Stuff
     }

test/diff/pattern/out.nix

@@ -62,46 +62,14 @@
     _
   )
   ({ }: _)
-  (
-    {
-      a,
-    }:
-    _
-  )
+  ({ a }: _)
   ({ }: _)
-  (
-    {
-      ...
-    }:
-    _
-  )
-  (
-    {
-      ...
-    }:
-    _
-  )
-  (
-    {
-      ...
-    }:
-    _
-  )
-  (
-    {
-      ...
-    }:
-    _
-  )
+  ({ ... }: _)
+  ({ ... }: _)
+  ({ ... }: _)
+  ({ ... }: _)
 
-  (
-    {
-      b,
-      e,
-      ...
-    }:
-    _
-  )
+  ({ b, e, ... }: _)
   (
     {
       b,