Expand let statements more

src/Nixfmt/Pretty.hs

@@ -188,6 +188,16 @@ absorbThen :: Expression -> Doc
 absorbThen (Term t) | isAbsorbable t = hardspace <> prettyTerm t <> hardspace
 absorbThen x                         = line <> nest 2 (group x) <> line
 
+-- What is allowed to come on the same line as `in`?
+-- Absorbable terms like sets
+-- if, with, let
+absorbIn :: Expression -> Doc
+absorbIn (Term t) | isAbsorbable t = hardspace <> prettyTerm t <> hardspace
+absorbIn x@(If _ _ _ _ _ _)        = group x
+absorbIn x@(With _ _ _ _)          = group x
+absorbIn x@(Let _ _ _ _)           = group x
+absorbIn x                         = line <> nest 2 (group x) <> line
+
 absorbElse :: Expression -> Doc
 absorbElse (If if_ cond then_ expr0 else_ expr1)
     = hardspace <> pretty if_ <> hardspace <> group cond <> hardspace
@@ -212,9 +222,9 @@ instance Pretty Expression where
 
     pretty (Let (Ann let_ letTrailing letLeading) binders
                 (Ann in_ inTrailing inLeading) expr)
-        = base $ group letPart <> line <> group inPart
-        where letPart = pretty let_ <> pretty letTrailing <> line <> letBody
-              inPart = pretty in_ <> hardspace <> pretty expr
+        = base $ group letPart <> line <> inPart
+        where letPart = pretty let_ <> pretty letTrailing <> hardline <> letBody
+              inPart = pretty in_ <> hardspace <> absorbIn expr
               letBody = nest 2 $
                   pretty letLeading
                   <> sepBy hardline binders

test/diff/apply/out.nix

@@ -14,8 +14,9 @@
               buildScript = "true";
               installMethod = "copy";
             });
-          in "${pkg}/lib/node_modules/${pname}/node_modules")
-        outputs.subPackages))
+          in
+            "${pkg}/lib/node_modules/${pname}/node_modules"
+        ) outputs.subPackages))
     }
   ''
   {

test/diff/comment/out.nix

@@ -71,7 +71,9 @@
 
     d = 1;
     #7
-  in d)
+  in
+    d
+  )
 
   ({
       a, # comment

test/diff/idioms_lib_2/out.nix

@@ -63,8 +63,11 @@ rec {
      final value.
   */
   pipe = val: functions:
-    let reverseApply = x: f: f x;
-    in builtins.foldl' reverseApply val functions;
+    let
+      reverseApply = x: f: f x;
+    in
+      builtins.foldl' reverseApply val functions
+  ;
 
   # note please don’t add a function like `compose = flip pipe`.
   # This would confuse users, because the order of the functions
@@ -175,7 +178,8 @@ rec {
   codeName = "Quokka";
 
   # Returns the current nixpkgs version suffix as string.
-  versionSuffix = let suffixFile = ../.version-suffix;
+  versionSuffix = let
+    suffixFile = ../.version-suffix;
   in if pathExists suffixFile then
     lib.strings.fileContents suffixFile
   else
@@ -352,12 +356,16 @@ rec {
      Type: String -> List ComparableVal -> List ComparableVal -> a -> a
   */
   checkListOfEnum = msg: valid: given:
-    let unexpected = lib.subtractLists valid given;
-    in lib.throwIfNot (unexpected == [ ]) "${msg}: ${
-      builtins.concatStringsSep ", " (builtins.map builtins.toString unexpected)
-    } unexpected; valid ones: ${
-      builtins.concatStringsSep ", " (builtins.map builtins.toString valid)
-    }";
+    let
+      unexpected = lib.subtractLists valid given;
+    in
+      lib.throwIfNot (unexpected == [ ]) "${msg}: ${
+        builtins.concatStringsSep ", "
+        (builtins.map builtins.toString unexpected)
+      } unexpected; valid ones: ${
+        builtins.concatStringsSep ", " (builtins.map builtins.toString valid)
+      }"
+  ;
 
   info = msg: builtins.trace "INFO: ${msg}";
 
@@ -422,7 +430,9 @@ rec {
             "14" = "E";
             "15" = "F";
           }.${toString d};
-    in lib.concatMapStrings toHexDigit (toBaseDigits 16 i);
+    in
+      lib.concatMapStrings toHexDigit (toBaseDigits 16 i)
+  ;
 
   /* `toBaseDigits base i` converts the positive integer i to a list of its
      digits in the given base. For example:
@@ -440,6 +450,10 @@ rec {
           let
             r = i - ((i / base) * base);
             q = (i - r) / base;
-          in [ r ] ++ go q;
-    in assert (base >= 2); assert (i >= 0); lib.reverseList (go i);
+          in
+            [ r ] ++ go q
+      ;
+    in
+      assert (base >= 2); assert (i >= 0); lib.reverseList (go i)
+  ;
 }

test/diff/idioms_lib_3/out.nix

@@ -98,9 +98,11 @@ in rec {
         k: v: map (mkLine k) (if lib.isList v then v else [ v ])
       else
         k: v: [ (mkLine k v) ];
-    in attrs:
-    libStr.concatStrings
-    (lib.concatLists (libAttr.mapAttrsToList mkLines attrs));
+    in
+      attrs:
+      libStr.concatStrings
+      (lib.concatLists (libAttr.mapAttrsToList mkLines attrs))
+  ;
 
   # Generate an INI-style config file from an
   # attrset of sections to an attrset of key-value pairs.
@@ -143,7 +145,9 @@ in rec {
           [${mkSectionName sectName}]
         '' + toKeyValue { inherit mkKeyValue listsAsDuplicateKeys; } sectValues;
       # map input to ini sections
-    in mapAttrsToStringsSep "\n" mkSection attrsOfAttrs;
+    in
+      mapAttrsToStringsSep "\n" mkSection attrsOfAttrs
+  ;
 
   # Generate an INI-style config file from an attrset
   # specifying the global section (no header), and an
@@ -233,8 +237,11 @@ in rec {
 
       # generation for multiple ini values
       mkKeyValue = k: v:
-        let mkKeyValue = mkKeyValueDefault { } " = " k;
-        in concatStringsSep "\n" (map (kv: "	" + mkKeyValue kv) (lib.toList v));
+        let
+          mkKeyValue = mkKeyValueDefault { } " = " k;
+        in
+          concatStringsSep "\n" (map (kv: "	" + mkKeyValue kv) (lib.toList v))
+      ;
 
       # converts { a.b.c = 5; } to { "a.b".c = 5; } for toINI
       gitFlattenAttrs = let
@@ -248,11 +255,15 @@ in rec {
           } else {
             ${head path} = value;
           };
-      in attrs:
-      lib.foldl lib.recursiveUpdate { } (lib.flatten (recurse [ ] attrs));
+      in
+        attrs:
+        lib.foldl lib.recursiveUpdate { } (lib.flatten (recurse [ ] attrs))
+      ;
 
       toINI_ = toINI { inherit mkKeyValue mkSectionName; };
-    in toINI_ (gitFlattenAttrs attrs);
+    in
+      toINI_ (gitFlattenAttrs attrs)
+  ;
 
   # Generates JSON from an arbitrary (non-function) value.
   # For more information see the documentation of the builtin.
@@ -293,14 +304,17 @@ in rec {
           id;
       mapAny = with builtins;
         depth: v:
-        let evalNext = x: mapAny (depth + 1) (transform (depth + 1) x);
+        let
+          evalNext = x: mapAny (depth + 1) (transform (depth + 1) x);
         in if isAttrs v then
           mapAttrs (stepIntoAttr evalNext) v
         else if isList v then
           map evalNext v
         else
           transform (depth + 1) v;
-    in mapAny 0;
+    in
+      mapAny 0
+  ;
 
   # Pretty print a value, akin to `builtins.trace`.
   # Should probably be a builtin as well.
@@ -360,10 +374,12 @@ in rec {
               # The last line gets a special treatment: if it's empty, '' is on its own line at the "outer"
               # indentation level. Otherwise, '' is appended to the last line.
               lastLine = lib.last escapedLines;
-            in "''" + introSpace
-            + concatStringsSep introSpace (lib.init escapedLines)
-            + (if lastLine == "" then outroSpace else introSpace + lastLine)
-            + "''";
+            in
+              "''" + introSpace
+              + concatStringsSep introSpace (lib.init escapedLines)
+              + (if lastLine == "" then outroSpace else introSpace + lastLine)
+              + "''"
+            ;
           in if multiline && length lines > 1 then
             multilineResult
           else
@@ -410,7 +426,9 @@ in rec {
               };") v) + outroSpace + "}"
         else
           abort "generators.toPretty: should never happen (v = ${v})";
-    in go indent;
+    in
+      go indent
+  ;
 
   # PLIST handling
   toPlist = { }:
@@ -462,29 +480,33 @@ in rec {
           (literal ind "</dict>")
         ];
 
-      attr = let attrFilter = name: value: name != "_module" && value != null;
-      in ind: x:
-      libStr.concatStringsSep "\n" (lib.flatten (lib.mapAttrsToList
-        (name: value:
-          lib.optionals (attrFilter name value) [
-            (key "	${ind}" name)
-            (expr "	${ind}" value)
-          ]) x));
+      attr = let
+        attrFilter = name: value: name != "_module" && value != null;
+      in
+        ind: x:
+        libStr.concatStringsSep "\n" (lib.flatten (lib.mapAttrsToList
+          (name: value:
+            lib.optionals (attrFilter name value) [
+              (key "	${ind}" name)
+              (expr "	${ind}" value)
+            ]) x))
+      ;
 
     in ''
       <?xml version="1.0" encoding="UTF-8"?>
       <!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
       <plist version="1.0">
       ${expr "" v}
-      </plist>'';
+      </plist>'' ;
 
   # Translate a simple Nix expression to Dhall notation.
   # Note that integers are translated to Integer and never
   # the Natural type.
   toDhall = { }@args:
     v:
     with builtins;
-    let concatItems = lib.strings.concatStringsSep ", ";
+    let
+      concatItems = lib.strings.concatStringsSep ", ";
     in if isAttrs v then
       "{ ${
         concatItems (lib.attrsets.mapAttrsToList

test/diff/idioms_nixos_1/out.nix

@@ -359,11 +359,14 @@ in {
       assertions = if config.boot.kernelPackages.kernel ? features then
         [ ]
       else
-        let cfg = config.boot.kernelPackages.kernel.config;
-        in map (attrs: {
-          assertion = attrs.assertion cfg;
-          inherit (attrs) message;
-        }) config.system.requiredKernelConfig;
+        let
+          cfg = config.boot.kernelPackages.kernel.config;
+        in
+          map (attrs: {
+            assertion = attrs.assertion cfg;
+            inherit (attrs) message;
+          }) config.system.requiredKernelConfig
+      ;
 
     })
 

test/diff/idioms_pkgs_3/out.nix

@@ -359,11 +359,14 @@ in {
       assertions = if config.boot.kernelPackages.kernel ? features then
         [ ]
       else
-        let cfg = config.boot.kernelPackages.kernel.config;
-        in map (attrs: {
-          assertion = attrs.assertion cfg;
-          inherit (attrs) message;
-        }) config.system.requiredKernelConfig;
+        let
+          cfg = config.boot.kernelPackages.kernel.config;
+        in
+          map (attrs: {
+            assertion = attrs.assertion cfg;
+            inherit (attrs) message;
+          }) config.system.requiredKernelConfig
+      ;
 
     })
 

test/diff/lambda/out.nix

@@ -39,7 +39,9 @@
       ...
     }:
     let
-    in pkgs)
+    in
+      pkgs
+  )
 
   (a:
     {

test/diff/let_in/out.nix

@@ -3,39 +3,61 @@ let
   a = let
     b = 2;
     c = 3;
-  in d;
-  a = let c = 1; in f;
+  in
+    d
+  ;
+  a = let
+    c = 1;
+  in
+    f
+  ;
 
   a = let
     c = 1;
     # e
-  in f;
-  a = let c = 1; # d
-  in f;
+  in
+    f
+  ;
+  a = let
+    c = 1; # d
+  in
+    f
+  ;
 
   a = let
     c = 1; # d
     # e
-  in f;
+  in
+    f
+  ;
   a = let # b
     c = 1;
-  in f;
+  in
+    f
+  ;
   a = let # b
     c = 1;
     # e
-  in f;
+  in
+    f
+  ;
   a = let # b
     c = 1; # d
-  in f;
+  in
+    f
+  ;
   a = let # b
     c = 1; # d
     # e
-  in f;
+  in
+    f
+  ;
 
   a = let
   in [
     1
     2
-  ];
+  ] ;
 
-in a
+in
+  a