Class modifiers (#1178)

* Format the new class modifiers.

* Update CHANGELOG.

Author: munificent

CHANGELOG.md

@@ -1,6 +1,7 @@
 # 2.2.5-dev
 
 * Format record expressions and record type annotations.
+* Format class modifiers `base`, `final`, `interface`, `mixin`, and `sealed`
 * Better indentation of multiline function types inside type argument lists. 
 * Require `package:analyzer` `^5.1.0`.
 * Format unnamed libraries.

lib/src/dart_formatter.dart

@@ -90,7 +90,9 @@ class DartFormatter {
     var featureSet = FeatureSet.fromEnableFlags2(
       sdkLanguageVersion: Version(2, 19, 0),
       flags: [
+        'class-modifiers',
         'records',
+        'sealed-class',
         'unnamed-libraries',
       ],
     );

lib/src/source_visitor.dart

@@ -596,6 +596,11 @@ class SourceVisitor extends ThrowingAstVisitor {
 
     builder.nestExpression();
     modifier(node.abstractKeyword);
+    modifier(node.baseKeyword);
+    modifier(node.interfaceKeyword);
+    modifier(node.finalKeyword);
+    modifier(node.sealedKeyword);
+    modifier(node.mixinKeyword);
     token(node.classKeyword);
     space();
     token(node.name);
@@ -615,6 +620,11 @@ class SourceVisitor extends ThrowingAstVisitor {
 
     _simpleStatement(node, () {
       modifier(node.abstractKeyword);
+      modifier(node.baseKeyword);
+      modifier(node.interfaceKeyword);
+      modifier(node.finalKeyword);
+      modifier(node.sealedKeyword);
+      modifier(node.mixinKeyword);
       token(node.typedefKeyword);
       space();
       token(node.name);
@@ -2142,6 +2152,10 @@ class SourceVisitor extends ThrowingAstVisitor {
     visitMetadata(node.metadata);
 
     builder.nestExpression();
+    modifier(node.baseKeyword);
+    modifier(node.interfaceKeyword);
+    modifier(node.finalKeyword);
+    modifier(node.sealedKeyword);
     token(node.mixinKeyword);
     space();
     token(node.name);

test/whitespace/classes.unit

@@ -169,4 +169,78 @@ class Foo {
 <<<
 class Foo {
   bar() {}
-}
+}
+>>> class modifiers
+class C1 {}
+base  class C2 {}
+interface  class C3 {}
+final  class C4 {}
+sealed  class C5 {}
+abstract  class C6 {}
+abstract  base  class C7 {}
+abstract  interface  class C8 {}
+abstract  final  class C9 {}
+mixin  class C10 {}
+base  mixin  class C11 {}
+abstract  mixin  class C12 {}
+abstract  base  mixin  class C13 {}
+<<<
+class C1 {}
+
+base class C2 {}
+
+interface class C3 {}
+
+final class C4 {}
+
+sealed class C5 {}
+
+abstract class C6 {}
+
+abstract base class C7 {}
+
+abstract interface class C8 {}
+
+abstract final class C9 {}
+
+mixin class C10 {}
+
+base mixin class C11 {}
+
+abstract mixin class C12 {}
+
+abstract base mixin class C13 {}
+>>> mixin application modifiers
+class C1 = Object with Mixin;
+base  class C2 = Object with Mixin;
+interface  class C3 = Object with Mixin;
+final  class C4 = Object with Mixin;
+sealed  class C5 = Object with Mixin;
+abstract  class C6 = Object with Mixin;
+abstract  base  class C7 = Object with Mixin;
+abstract interface  class C8 = Object with Mixin;
+abstract  final  class C9 = Object with Mixin;
+mixin  class C10 = Object with Mixin;
+base  mixin  class C11 = Object with Mixin;
+abstract  mixin  class C12 = Object with Mixin;
+abstract  base  mixin  class C13 = Object with Mixin;
+<<<
+class C1 = Object with Mixin;
+base class C2 = Object with Mixin;
+interface class C3 = Object with Mixin;
+final class C4 = Object with Mixin;
+sealed class C5 = Object with Mixin;
+abstract class C6 = Object with Mixin;
+abstract base class C7 = Object
+    with Mixin;
+abstract interface class C8 = Object
+    with Mixin;
+abstract final class C9 = Object
+    with Mixin;
+mixin class C10 = Object with Mixin;
+base mixin class C11 = Object
+    with Mixin;
+abstract mixin class C12 = Object
+    with Mixin;
+abstract base mixin class C13 = Object
+    with Mixin;

test/whitespace/mixins.unit

@@ -24,4 +24,16 @@ mixin M1 on UnaryNum {
 >>> generic
 mixin M<   A  ,B  >on   C  implements    D{ }
 <<<
-mixin M<A, B> on C implements D {}
+mixin M<A, B> on C implements D {}
+>>> mixin modifiers
+mixin  M1 {}
+base  mixin M2 {}
+interface  mixin M3 {}
+final  mixin M4 {}
+sealed  mixin M5 {}
+<<<
+mixin M1 {}
+base mixin M2 {}
+interface mixin M3 {}
+final mixin M4 {}
+sealed mixin M5 {}