feat: enforce empty set/list style

CHANGELOG.md

@@ -1,3 +1,12 @@
+Unreleased / YYYY-MM-DD
+=======================
+
+### Formatting changes
+
+* Empty sets: `{ }`
+  and lists: `[ ]`
+  are now formatted as: `{}`
+  and: `[]` respectively (#264)
 
 1.2.0 / 2021-03-29
 ==================

src/rules.rs

@@ -54,10 +54,10 @@ pub(crate) fn spacing() -> SpacingDsl {
         .test("[1 2 3]", "[ 1 2 3 ]")
         .inside(NODE_LIST).after(T!["["]).single_space_or_newline()
         .inside(NODE_LIST).before(T!["]"]).single_space_or_newline()
+        .test("[]", "[]")
+        .inside(NODE_LIST).between(T!["["], T!["]"]).no_space()
         .inside(NODE_LIST).after(T!["["]).when(inline_with_attr_set).no_space()
         .inside(NODE_LIST).before(T!["]"]).when(inline_with_attr_set).no_space()
-        .test("[]", "[ ]")
-        .inside(NODE_LIST).between(T!["["], T!["]"]).single_space_or_optional_newline()
         .inside(NODE_LIST).between(VALUES, VALUES).single_space_or_newline()
         .inside(NODE_LIST).between(VALUES, TOKEN_COMMENT).single_space_or_optional_newline()
         .inside(NODE_LIST).between(TOKEN_COMMENT, VALUES).single_space_or_newline()
@@ -72,8 +72,8 @@ pub(crate) fn spacing() -> SpacingDsl {
         .test("{foo = 92;}", "{ foo = 92; }")
         .inside(NODE_ATTR_SET).after(T!["{"]).single_space_or_newline()
         .inside(NODE_ATTR_SET).before(T!["}"]).single_space_or_newline()
-        .test("{}", "{ }")
-        .inside(NODE_ATTR_SET).between(T!["{"], T!["}"]).single_space()
+        .test("{}", "{}")
+        .inside(NODE_ATTR_SET).between(T!["{"], T!["}"]).no_space()
         .inside(NODE_ATTR_SET).before(NODE_KEY_VALUE).single_space_or_optional_newline()
         .inside(NODE_ATTR_SET).between(NODE_KEY_VALUE, NODE_KEY_VALUE).single_space_or_newline()
         .inside(NODE_ATTR_SET).between(NODE_INHERIT, [NODE_INHERIT, TOKEN_COMMENT]).single_space_or_optional_newline()
@@ -120,7 +120,7 @@ pub(crate) fn spacing() -> SpacingDsl {
         .inside(NODE_IF_ELSE).around([T![else],T![then]]).single_space_or_optional_newline()
         .inside(NODE_IF_ELSE).after(T![then]).when(has_expression_node).single_space_or_newline()
         .inside(NODE_IF_ELSE).after(T![else]).when(has_expression_node).single_space_or_newline()
-        
+
         // special-case to force a linebreak before `=` in
         //
         // ```nix
@@ -434,7 +434,7 @@ pub(crate) fn indentation() -> IndentDsl {
                   92
                 )
             "#)
-        
+
         .rule("Indent attribute set content")
             .inside(NODE_ATTR_SET)
             .not_matching([T!["{"], T!["}"]])

test_data/indent_or_default.good.nix

@@ -1,4 +1,4 @@
 {
   catAttrs = builtins.catAttrs or
-    (attr: l: concatLists (map (s: if s ? ${attr} then [ s.${attr} ] else [ ]) l));
+    (attr: l: concatLists (map (s: if s ? ${attr} then [ s.${attr} ] else []) l));
 }

test_data/indent_paren.good.nix

@@ -19,7 +19,7 @@
           a
           (attrNames n)
       )
-      { }
+      {}
       list_of_attrs;
   bar = fun "arg" (callPackage ./. {
     inherit foo;

test_data/indented_lambda.bad.nix

@@ -8,8 +8,8 @@
     else "--${k}"
 , mkOption ? k: v:
   if v == null
-  then [ ]
-  else [ (mkOptionName k) (lib.generators.mkValueStringDefault { } v) ]
+  then []
+  else [ (mkOptionName k) (lib.generators.mkValueStringDefault {} v) ]
 }:
 {  toINI = {
   # parameter comment

test_data/indented_lambda.good.nix

@@ -8,15 +8,15 @@
     else "--${k}"
 , mkOption ? k: v:
     if v == null
-    then [ ]
-    else [ (mkOptionName k) (lib.generators.mkValueStringDefault { } v) ]
+    then []
+    else [ (mkOptionName k) (lib.generators.mkValueStringDefault {} v) ]
 }:
 {
   toINI =
     {
       # parameter comment
       mkSectionName ? (name: libStr.escape [ "[" "]" ] name)
-    , mkKeyValue ? mkKeyValueDefault { } "="
+    , mkKeyValue ? mkKeyValueDefault {} "="
     }: attrsOfAttrs:
     mapAttrsToStringsSep "\n" mkSection attrsOfAttrs;
 }

test_data/issue-132.good.nix

@@ -1,6 +1,5 @@
 {
-  buildInputs = [
-  ] ++ stdenv.lib.optionals enableGui (with qt5; [ qtbase qtwebkit ])
-  ++ stdenv.lib.optionals enableJupyter [ boost jsoncpp openssl zmqpp ]
+  buildInputs = [] ++ stdenv.lib.optionals enableGui (with qt5; [ qtbase qtwebkit ])
+    ++ stdenv.lib.optionals enableJupyter [ boost jsoncpp openssl zmqpp ]
   ;
 }

test_data/issue-185.bad.nix

@@ -1,4 +1,4 @@
 {
 attrs = {};
-lists = [ ];
+lists = [];
 }

test_data/issue-185.good.nix

@@ -1,4 +1,4 @@
 {
-  attrs = { };
-  lists = [ ];
+  attrs = {};
+  lists = [];
 }

test_data/issue-199.good.nix

@@ -29,4 +29,4 @@ let
 
 
 in
-{ }
+{}

test_data/issue-205.bad.nix

@@ -9,4 +9,4 @@ let
     inherit foo;bar = baz;
   };
 in
-{ }
+{}

test_data/issue-205.good.nix

@@ -9,4 +9,4 @@ let
     inherit foo; bar = baz;
   };
 in
-{ }
+{}

test_data/list_elements.good.nix

@@ -1,6 +1,6 @@
 [
   1
-  [ ]
+  []
   { a = 92; }
   "hello"
   foo.bar

test_data/nested_indent.bad.nix

@@ -1,5 +1,5 @@
 {
-  pkgs ? import ./nix/nixpkgs.nix { },
+  pkgs ? import ./nix/nixpkgs.nix {},
   src ? builtins.fetchGit {
     url = ./.;
     ref = "HEAD";

test_data/nested_indent.good.nix

@@ -1,7 +1,7 @@
-{ pkgs ? import ./nix/nixpkgs.nix { }
+{ pkgs ? import ./nix/nixpkgs.nix {}
 , src ? builtins.fetchGit {
     url = ./.;
     ref = "HEAD";
   }
 }:
-pkgs.example rec { }
+pkgs.example rec {}

test_data/nixpkgs_repository/doc_shellnix.good.nix

@@ -1,5 +1,5 @@
-{ pkgs ? import ../. { } }:
-(import ./default.nix { }).overrideAttrs (x: {
+{ pkgs ? import ../. {} }:
+(import ./default.nix {}).overrideAttrs (x: {
   buildInputs = x.buildInputs ++ [ pkgs.xmloscopy pkgs.ruby ];
 
 })

test_data/nixpkgs_repository/lib_customisation.bad.nix

@@ -4,16 +4,16 @@
       newDrv = derivation (drv.drvAttrs // (f drv));
     in lib.flip (extendDerivation true) newDrv (
       {
-        meta = drv.meta or { };
-        passthru = if drv ? passthru then drv.passthru else { };
+        meta = drv.meta or {};
+        passthru = if drv ? passthru then drv.passthru else {};
       }
       //
-      (drv.passthru or { })
+      (drv.passthru or {})
       //
       (if (drv ? crossDrv && drv ? nativeDrv)
   then {
      crossDrv = overrideDerivation drv.crossDrv f;
      nativeDrv = overrideDerivation drv.nativeDrv f;
   }
-   else { }));
+   else {}));
 }

test_data/nixpkgs_repository/lib_customisation.good.nix

@@ -5,17 +5,17 @@
     in
     lib.flip (extendDerivation true) newDrv (
       {
-        meta = drv.meta or { };
-        passthru = if drv ? passthru then drv.passthru else { };
+        meta = drv.meta or {};
+        passthru = if drv ? passthru then drv.passthru else {};
       }
       //
-      (drv.passthru or { })
+      (drv.passthru or {})
       //
       (if (drv ? crossDrv && drv ? nativeDrv)
       then {
         crossDrv = overrideDerivation drv.crossDrv f;
         nativeDrv = overrideDerivation drv.nativeDrv f;
       }
-      else { })
+      else {})
     );
 }

test_data/nixpkgs_repository/lib_deprecated.good.nix

@@ -1,6 +1,6 @@
 {
   innerClosePropagation = acc: xs:
-    if xs == [ ]
+    if xs == []
     then acc
     else
       let
@@ -14,8 +14,8 @@
         in innerClosePropagation
           acc'
           (uniqList {
-            inputList = (maybeAttrNullable "propagatedBuildInputs" [ ] y)
-              ++ (maybeAttrNullable "propagatedNativeBuildInputs" [ ] y)
+            inputList = (maybeAttrNullable "propagatedBuildInputs" [] y)
+              ++ (maybeAttrNullable "propagatedNativeBuildInputs" [] y)
               ++ ys;
             acc = acc';
           });

test_data/nixpkgs_repository/nixpkgs_idempotent.good.nix

@@ -2,7 +2,7 @@
 # Operations on attribute sets.
 rec {
   filterAttrs = pred: set:
-    listToAttrs (concatMap (name: let v = set.${name}; in if pred name v then [ (nameValuePair name v) ] else [ ]) (attrNames set));
+    listToAttrs (concatMap (name: let v = set.${name}; in if pred name v then [ (nameValuePair name v) ] else []) (attrNames set));
 
   inherit (self.trivial) id const pipe concat or and bitAnd bitOr bitXor;
 }

test_data/syntax_errors/issue-93.good.nix

@@ -1 +1 @@
-{ } =
+{} =

test_data/top_level_with2.good.nix

@@ -1,4 +1,4 @@
-with import <nixpkgs> { };
+with import <nixpkgs> {};
 stdenv.mkDerivation {
   name = "rnix";
   buildInputs = [ cargo ];