feat: no space in empty containers

[kamadorueda]

diff --git a/doc/default.nix b/doc/default.nix
index 53e101994..c485d486e 100644
--- a/doc/default.nix
+++ b/doc/default.nix
@@ -1,6 +1,6 @@
 {
-  pkgs ? (import ./.. { }),
-  nixpkgs ? { },
+  pkgs ? (import ./.. {}),
+  nixpkgs ? {},
 }:
 let
   lib = pkgs.lib;
diff --git a/doc/doc-support/default.nix b/doc/doc-support/default.nix
index ce7c3359b..4a7cf537e 100644
--- a/doc/doc-support/default.nix
+++ b/doc/doc-support/default.nix
@@ -1,6 +1,6 @@
 {
-  pkgs ? (import ../.. { }),
-  nixpkgs ? { },
+  pkgs ? (import ../.. {}),
+  nixpkgs ? {},
 }:
 let
   locationsXml = import ./lib-function-locations.nix { inherit pkgs nixpkgs; };
@@ -27,7 +27,7 @@ let
     </xsl:stylesheet>
   '';
 in
-pkgs.runCommand "doc-support" { }
+pkgs.runCommand "doc-support" {}
 ''
   mkdir result
   (
diff --git a/doc/doc-support/lib-function-docs.nix b/doc/doc-support/lib-function-docs.nix
index c634611dc..2c84abfc3 100644
--- a/doc/doc-support/lib-function-docs.nix
+++ b/doc/doc-support/lib-function-docs.nix
@@ -2,7 +2,7 @@
 # another library function file to this list, the include list in the
 # file `doc/functions/library.xml` must also be updated.
 {
-  pkgs ? import ./.. { },
+  pkgs ? import ./.. {},
   locationsXml,
 }:
 with pkgs;
@@ -10,7 +10,7 @@ stdenv.mkDerivation {
   name = "nixpkgs-lib-docs";
   src = ./../../lib;
 
-  buildInputs = [ nixdoc ];
+  buildInputs = [nixdoc];
   installPhase = ''
     function docgen {
       nixdoc -c "$1" -d "$2" -f "../lib/$1.nix"  > "$out/$1.xml"
diff --git a/doc/doc-support/lib-function-locations.nix b/doc/doc-support/lib-function-locations.nix
index 815a8f3a7..5528d1ef9 100644
--- a/doc/doc-support/lib-function-locations.nix
+++ b/doc/doc-support/lib-function-locations.nix
@@ -1,6 +1,6 @@
 {
-  pkgs ? (import ./.. { }),
-  nixpkgs ? { },
+  pkgs ? (import ./.. {}),
+  nixpkgs ? {},
 }:
 let
   revision = pkgs.lib.trivial.revisionWithDefault (nixpkgs.revision or "master");
@@ -76,8 +76,8 @@ let
 
   relativeLocs = (builtins.map fnLocationRelative liblocations);
   sanitizeId = builtins.replaceStrings
-  [ "'" ]
-  [ "-prime" ];
+  ["'"]
+  ["-prime"];
 
   urlPrefix = "https://github.com/NixOS/nixpkgs/blob/${revision}";
   xmlstrings = (
diff --git a/doc/shell.nix b/doc/shell.nix
index 5fa2b4424..eef0a2b03 100644
--- a/doc/shell.nix
+++ b/doc/shell.nix
@@ -1,3 +1,3 @@
-{ pkgs ? import ../. { } }:
-(import ./default.nix { }).overrideAttrs
-(x: { buildInputs = (x.buildInputs or [ ]) ++ [ pkgs.xmloscopy pkgs.ruby ]; })
+{ pkgs ? import ../. {} }:
+(import ./default.nix {}).overrideAttrs
+(x: { buildInputs = (x.buildInputs or []) ++ [pkgs.xmloscopy pkgs.ruby]; })
diff --git a/lib/asserts.nix b/lib/asserts.nix
index 223e9dc7c..b6b7f4f8b 100644
--- a/lib/asserts.nix
+++ b/lib/asserts.nix
@@ -37,8 +37,8 @@ rec {
     assertMsg
     (lib.elem val xs)
     "${name} must be one of ${
-      lib.generators.toPretty { } xs
+      lib.generators.toPretty {} xs
     }, but is: ${
-      lib.generators.toPretty { } val
+      lib.generators.toPretty {} val
     }";
 }
diff --git a/lib/attrsets.nix b/lib/attrsets.nix
index 65fe860a1..7725a2b56 100644
--- a/lib/attrsets.nix
+++ b/lib/attrsets.nix
@@ -22,7 +22,7 @@ rec {
   attrByPath = attrPath: default: e: let
     attr = head attrPath;
   in
-    if attrPath == [ ]
+    if attrPath == []
     then e
     else if e ? ${attr}
     then attrByPath (tail attrPath) default e.${attr}
@@ -42,7 +42,7 @@ rec {
   hasAttrByPath = attrPath: e: let
     attr = head attrPath;
   in
-    if attrPath == [ ]
+    if attrPath == []
     then true
     else if e ? ${attr}
     then hasAttrByPath (tail attrPath) e.${attr}
@@ -125,8 +125,8 @@ rec {
           map (
             s:
               if s ? ${attr}
-              then [ s.${attr} ]
-              else [ ]
+              then [s.${attr}]
+              else []
           )
           l
         )
@@ -147,8 +147,8 @@ rec {
           v = set.${name};
         in
           if pred name v
-          then [ (nameValuePair name v) ]
-          else [ ]
+          then [(nameValuePair name v)]
+          else []
       ) (attrNames set)
     );
 
@@ -177,7 +177,7 @@ rec {
                 )
               )
             ]
-          else [ ]
+          else []
       ) (attrNames set)
     );
 
@@ -196,7 +196,7 @@ rec {
             o // { ${name} = op n.${name} (a.${name} or nul); }
         )
         a (attrNames n)
-    ) { };
+    ) {};
 
   /*
    Recursively collect sets that verify a given predicate named `pred'
@@ -217,10 +217,10 @@ rec {
    */
   collect = pred: attrs:
     if pred attrs
-    then [ attrs ]
+    then [attrs]
     else if isAttrs attrs
     then concatMap (collect pred) (attrValues attrs)
-    else [ ];
+    else [];
 
   /*
     Return the cartesian product of attribute set value combinations.
@@ -242,7 +242,7 @@ rec {
             map (listValue: attrs // { ${attrName} = listValue; }) attrsOfLists.${attrName}
         )
         listOfAttrs
-    ) [ { } ] (attrNames attrsOfLists);
+    ) [{}] (attrNames attrsOfLists);
 
   /*
    Utility function that creates a {name, value} pair as expected by
@@ -348,12 +348,12 @@ rec {
       g =
         name: value:
           if isAttrs value && cond value
-          then recurse (path ++ [ name ]) value
-          else f (path ++ [ name ]) value;
+          then recurse (path ++ [name]) value
+          else f (path ++ [name]) value;
     in
       mapAttrs g;
   in
-    recurse [ ] set;
+    recurse [] set;
 
   /*
    Generate an attribute set by mapping a function over a list of
@@ -389,7 +389,7 @@ rec {
         type = "derivation";
         name = sanitizeDerivationName (builtins.substring 33 (-1) (baseNameOf path'));
         outPath = path';
-        outputs = [ "out" ];
+        outputs = ["out"];
         out = res;
         outputName = "out";
       };
@@ -409,7 +409,7 @@ rec {
   optionalAttrs = cond: as:
     if cond
     then as
-    else { };
+    else {};
 
   /*
    Merge sets of attributes and use the function f to merge attributes
@@ -484,7 +484,7 @@ rec {
     f = attrPath:
       zipAttrsWith (
         n: values: let
-          here = attrPath ++ [ n ];
+          here = attrPath ++ [n];
         in
           if
             length values
@@ -494,7 +494,7 @@ rec {
           else f here values
       );
   in
-    f [ ] [ rhs lhs ];
+    f [] [rhs lhs];
 
   /*
    A recursive variant of the update operator ‘//’.  The recursion
@@ -539,7 +539,7 @@ rec {
             else if isAttrs pat
             then isAttrs val && matchAttrs pat val
             else pat == val
-        ) [ pattern attrs ]
+        ) [pattern attrs]
       )
     );
 
diff --git a/lib/cli.nix b/lib/cli.nix
index d8aefb808..de28a2f97 100644
--- a/lib/cli.nix
+++ b/lib/cli.nix
@@ -68,8 +68,8 @@ rec {
       mkOption ?
         k: v:
           if v == null
-          then [ ]
-          else [ (mkOptionName k) (lib.generators.mkValueStringDefault { } v) ],
+          then []
+          else [(mkOptionName k) (lib.generators.mkValueStringDefault {} v)],
     }:
       options: let
         render = k: v:
diff --git a/lib/customisation.nix b/lib/customisation.nix
index 7c5f2386e..3929494a2 100644
--- a/lib/customisation.nix
+++ b/lib/customisation.nix
@@ -31,13 +31,13 @@ rec {
   in
     lib.flip (extendDerivation true) newDrv (
       {
-        meta = drv.meta or { };
+        meta = drv.meta or {};
         passthru =
           if drv ? passthru
           then drv.passthru
-          else { };
+          else {};
       }
-      // (drv.passthru or { })
+      // (drv.passthru or {})
       // (
         if (drv ? crossDrv && drv ? nativeDrv)
         then
@@ -45,7 +45,7 @@ rec {
             crossDrv = overrideDerivation drv.crossDrv f;
             nativeDrv = overrideDerivation drv.nativeDrv f;
           }
-        else { }
+        else {}
       )
     );
 
@@ -170,7 +170,7 @@ rec {
    the derivation itself and check a given condition when evaluating.
    */
   extendDerivation = condition: passthru: drv: let
-    outputs = drv.outputs or [ "out" ];
+    outputs = drv.outputs or ["out"];
 
     commonAttrs =
       drv
@@ -205,7 +205,7 @@ rec {
    garbage collection.
    */
   hydraJob = drv: let
-    outputs = drv.outputs or [ "out" ];
+    outputs = drv.outputs or ["out"];
 
     commonAttrs =
       {
@@ -255,7 +255,7 @@ rec {
       f self
       // {
         newScope = scope: newScope (self // scope);
-        callPackage = self.newScope { };
+        callPackage = self.newScope {};
         overrideScope = g:
           lib.warn
           "`overrideScope` (from `lib.makeScope`) is deprecated. Do `overrideScope' (self: super: { … })` instead of `overrideScope (super: self: { … })`. All other overrides have the parameters in that order, including other definitions of `overrideScope`. This was the only definition violating the pattern."
diff --git a/lib/debug.nix b/lib/debug.nix
index 59c131a14..4ec26386d 100644
--- a/lib/debug.nix
+++ b/lib/debug.nix
@@ -224,11 +224,11 @@ rec {
       testsToRun =
         if tests ? tests
         then tests.tests
-        else [ ];
+        else [];
     in
       if
         (substring 0 4 name == "test" || elem name testsToRun)
-        && ((testsToRun == [ ]) || elem name tests.tests)
+        && ((testsToRun == []) || elem name tests.tests)
         && (test.expr != test.expected)
       then
         [
@@ -238,7 +238,7 @@ rec {
             result = test.expr;
           }
         ]
-      else [ ]) tests));
+      else []) tests));
 
   /*
    Create a test assuming that list elements are `true`.
@@ -288,7 +288,7 @@ rec {
                 (attrNames drv)
               }>"
             )
-          else if [ ] == v
+          else if [] == v
           then pr (const "[]")
           else if isList v
           then pr (l: "[ ${go (head l)}, … ]")
diff --git a/lib/deprecated.nix b/lib/deprecated.nix
index fbd45f3d5..db09545bd 100644
--- a/lib/deprecated.nix
+++ b/lib/deprecated.nix
@@ -22,13 +22,13 @@ with lib.strings; rec {
     arg = (merger init (defaultMergeArg init x));
     # now add the function with composed args already applied to the final attrs
     base = (
-      setAttrMerge "passthru" { } (f arg)
+      setAttrMerge "passthru" {} (f arg)
       (
         z:
           z
           // {
             function = foldArgs merger f arg;
-            args = (lib.attrByPath [ "passthru" "args" ] { } z) // x;
+            args = (lib.attrByPath ["passthru" "args"] {} z) // x;
           }
       )
     );
@@ -52,9 +52,9 @@ with lib.strings; rec {
     if cond
     then val
     else if builtins.isList val
-    then [ ]
+    then []
     else if builtins.isAttrs val
-    then { }
+    then {}
     # else if builtins.isString val then ""
     else if val == true || val == false
     then false
@@ -66,17 +66,17 @@ with lib.strings; rec {
     then true
     else if name == "false"
     then false
-    else if (elem name (attrByPath [ "flags" ] [ ] attrSet))
+    else if (elem name (attrByPath ["flags"] [] attrSet))
     then true
-    else attrByPath [ name ] false attrSet;
+    else attrByPath [name] false attrSet;
 
   # Input : attrSet, [ [name default] ... ], name
   # Output : its value or default.
   getValue = attrSet: argList: name: (
-    attrByPath [ name ] (
+    attrByPath [name] (
       if checkFlag attrSet name
       then true
-      else if argList == [ ]
+      else if argList == []
       then null
       else
         let
@@ -127,19 +127,19 @@ with lib.strings; rec {
   uniqList =
     {
       inputList,
-      acc ? [ ],
+      acc ? [],
     }:
     let
       go = xs: acc:
-        if xs == [ ]
-        then [ ]
+        if xs == []
+        then []
         else
           let
             x = head xs;
             y =
               if elem x acc
-              then [ ]
-              else [ x ];
+              then []
+              else [x];
           in
             y ++ go (tail xs) (y ++ acc);
     in
@@ -148,11 +148,11 @@ with lib.strings; rec {
   uniqListExt =
     {
       inputList,
-      outputList ? [ ],
+      outputList ? [],
       getter ? (x: x),
       compare ? (x: y: x == y),
     }:
-      if inputList == [ ]
+      if inputList == []
       then outputList
       else
         let
@@ -162,8 +162,8 @@ with lib.strings; rec {
             outputList
             ++ (
               if any isX outputList
-              then [ ]
-              else [ x ]
+              then []
+              else [x]
             );
         in
           uniqListExt {
@@ -173,7 +173,7 @@ with lib.strings; rec {
           };
 
   condConcat = name: list: checker:
-    if list == [ ]
+    if list == []
     then name
     else if checker (head list)
     then
@@ -193,7 +193,7 @@ with lib.strings; rec {
     }:
     let
       work = list: doneKeys: result:
-        if list == [ ]
+        if list == []
         then result
         else
           let
@@ -202,18 +202,18 @@ with lib.strings; rec {
           in
             if elem key doneKeys
             then work (tail list) doneKeys result
-            else work (tail list ++ operator x) ([ key ] ++ doneKeys) ([ x ] ++ result);
+            else work (tail list ++ operator x) ([key] ++ doneKeys) ([x] ++ result);
     in
-      work startSet [ ] [ ];
+      work startSet [] [];
 
   innerModifySumArgs = f: x: a: b:
     if b == null
     then (f a b) // x
     else innerModifySumArgs f x (a // b);
-  modifySumArgs = f: x: innerModifySumArgs f x { };
+  modifySumArgs = f: x: innerModifySumArgs f x {};
 
   innerClosePropagation = acc: xs:
-    if xs == [ ]
+    if xs == []
     then acc
     else
       let
@@ -224,27 +224,27 @@ with lib.strings; rec {
         then innerClosePropagation acc ys
         else
           let
-            acc' = [ y ] ++ acc;
+            acc' = [y] ++ acc;
           in
             innerClosePropagation
             acc'
             (
               uniqList {
                 inputList =
-                  (maybeAttrNullable "propagatedBuildInputs" [ ] y)
-                  ++ (maybeAttrNullable "propagatedNativeBuildInputs" [ ] y)
+                  (maybeAttrNullable "propagatedBuildInputs" [] y)
+                  ++ (maybeAttrNullable "propagatedNativeBuildInputs" [] y)
                   ++ ys;
                 acc = acc';
               }
             );
 
-  closePropagation = list: (uniqList { inputList = (innerClosePropagation [ ] list); });
+  closePropagation = list: (uniqList { inputList = (innerClosePropagation [] list); });
 
   # calls a function (f attr value ) for each record item. returns a list
   mapAttrsFlatten = f: r: map (attr: f attr r.${attr}) (attrNames r);
 
   # attribute set containing one attribute
-  nvs = name: value: listToAttrs [ (nameValuePair name value) ];
+  nvs = name: value: listToAttrs [(nameValuePair name value)];
   # adds / replaces an attribute of an attribute set
   setAttr = set: name: v: set // (nvs name v);
 
@@ -279,8 +279,8 @@ with lib.strings; rec {
   # ! deprecated, use mergeAttrByFunc instead
   mergeAttrsNoOverride =
     {
-      mergeLists ? [ "buildInputs" "propagatedBuildInputs" ],
-      overrideSnd ? [ "buildPhase" ],
+      mergeLists ? ["buildInputs" "propagatedBuildInputs"],
+      overrideSnd ? ["buildPhase"],
     }:
       attrs1: attrs2:
         foldr (
@@ -315,10 +315,10 @@ with lib.strings; rec {
   mergeAttrByFunc = x: y: let
     mergeAttrBy2 =
       { mergeAttrBy = lib.mergeAttrs; }
-      // (maybeAttr "mergeAttrBy" { } x)
-      // (maybeAttr "mergeAttrBy" { } y);
+      // (maybeAttr "mergeAttrBy" {} x)
+      // (maybeAttr "mergeAttrBy" {} y);
   in
-    foldr lib.mergeAttrs { } [
+    foldr lib.mergeAttrs {} [
       x
       y
       (
@@ -345,17 +345,17 @@ with lib.strings; rec {
       )
     ];
   mergeAttrsByFuncDefaults = foldl mergeAttrByFunc { inherit mergeAttrBy; };
-  mergeAttrsByFuncDefaultsClean = list: removeAttrs (mergeAttrsByFuncDefaults list) [ "mergeAttrBy" ];
+  mergeAttrsByFuncDefaultsClean = list: removeAttrs (mergeAttrsByFuncDefaults list) ["mergeAttrBy"];
 
   # sane defaults (same name as attr name so that inherit can be used)
   mergeAttrBy =
     # { buildInputs = concatList; [...]; passthru = mergeAttr; [..]; }
     listToAttrs (
       map (n: nameValuePair n lib.concat)
-      [ "nativeBuildInputs" "buildInputs" "propagatedBuildInputs" "configureFlags" "prePhases" "postAll" "patches" ]
+      ["nativeBuildInputs" "buildInputs" "propagatedBuildInputs" "configureFlags" "prePhases" "postAll" "patches"]
     )
-    // listToAttrs (map (n: nameValuePair n lib.mergeAttrs) [ "passthru" "meta" "cfg" "flags" ])
-    // listToAttrs (map (n: nameValuePair n (a: b: "${a}\n${b}")) [ "preConfigure" "postInstall" ]);
+    // listToAttrs (map (n: nameValuePair n lib.mergeAttrs) ["passthru" "meta" "cfg" "flags"])
+    // listToAttrs (map (n: nameValuePair n (a: b: "${a}\n${b}")) ["preConfigure" "postInstall"]);
 
   nixType = x:
     if isAttrs x
diff --git a/lib/fixed-points.nix b/lib/fixed-points.nix
index 58149a9c6..5ced3d25d 100644
--- a/lib/fixed-points.nix
+++ b/lib/fixed-points.nix
@@ -87,7 +87,7 @@ rec {
   # composeManyExtensions : [packageSet -> packageSet -> packageSet] -> packageSet -> packageSet -> packageSet
   #                          ^final        ^prev         ^overrides     ^final        ^prev         ^overrides
   composeManyExtensions =
-    lib.foldr (x: y: composeExtensions x y) (final: prev: { });
+    lib.foldr (x: y: composeExtensions x y) (final: prev: {});
 
   # Create an overridable, recursive attribute set. For example:
   #
diff --git a/lib/generators.nix b/lib/generators.nix
index c5ad54699..c760276b7 100644
--- a/lib/generators.nix
+++ b/lib/generators.nix
@@ -29,12 +29,12 @@ in
      * The builtin `toString` function has some strange defaults,
      * suitable for bash scripts but not much else.
      */
-    mkValueStringDefault = { }: v: with builtins; let
+    mkValueStringDefault = {}: v: with builtins; let
       err = t: v:
         abort
         (
           "generators.mkValueStringDefault: "
-          + "${t} not supported: ${toPretty { } v}"
+          + "${t} not supported: ${toPretty {} v}"
         );
     in
       if isInt v
@@ -79,7 +79,7 @@ in
      * mkKeyValueDefault {} ":" "f:oo" "bar"
      * > "f\:oo:bar"
      */
-    mkKeyValueDefault = { mkValueString ? mkValueStringDefault { } }: sep: k: v: "${libStr.escape [ sep ] k}${sep}${mkValueString v}";
+    mkKeyValueDefault = { mkValueString ? mkValueStringDefault {} }: sep: k: v: "${libStr.escape [sep] k}${sep}${mkValueString v}";
 
     ## -- FILE FORMAT GENERATORS --
 
@@ -90,7 +90,7 @@ in
      */
     toKeyValue =
       {
-        mkKeyValue ? mkKeyValueDefault { } "=",
+        mkKeyValue ? mkKeyValueDefault {} "=",
         listsAsDuplicateKeys ? false,
       }:
       let