Prettier style trailing commas (#1284)

This pull request addresses the issue described in [Issue
#668](#668) and [Issue #1285
](#1285).
A flag UsePrettierStyleTrailingCommas is introduced which ensures a
trailing comma for anonymous object/collection/initializer/switch
expressions, list patterns and enum declarations in the case a line
break occurs.

I hope the implementation of the feature isn't too invasive. Obviously
it would be easier to implement the feature non-configurable.

I'm not sure how to deal with the tests, for now I enabled the flag and
adjusted the corresponding tests.

Thanks for any feedback!

---------

Co-authored-by: Bela VanderVoort <bela.vandervoort@optimizely.com>

Src/CSharpier.FakeGenerators/SyntaxNodeComparerGenerator.cs

@@ -232,8 +232,9 @@ private static void GenerateMethod(StringBuilder sourceBuilder, Type type)
                 );
                 sourceBuilder.AppendLine($"            if (result.IsInvalid) return result;");
 
+                // Omit the last separator when comparing the original node with the formatted node, as it legitimately may be added or removed
                 sourceBuilder.AppendLine(
-                    $"            result = this.CompareLists(originalNode.{propertyName}.GetSeparators().ToList(), formattedNode.{propertyName}.GetSeparators().ToList(), Compare, o => o.Span, originalNode.Span, formattedNode.Span);"
+                    $"            result = this.CompareLists(originalNode.{propertyName}.GetSeparators().Take(originalNode.{propertyName}.Count() - 1).ToList(), formattedNode.{propertyName}.GetSeparators().Take(formattedNode.{propertyName}.Count() - 1).ToList(), Compare, o => o.Span, originalNode.Span, formattedNode.Span);"
                 );
                 sourceBuilder.AppendLine($"            if (result.IsInvalid) return result;");
             }

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/AnonymousObjectCreationExpressions.test

@@ -6,7 +6,7 @@ public class ClassName
     {
         One = "One",
         Two = "Two",
-        ThreeThreeThree = "ThreeThreeThree"
+        ThreeThreeThree = "ThreeThreeThree",
     };
 
     public dynamic Value = new { NoName };

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/ArgumentLists.test

@@ -30,20 +30,20 @@ public class ClassName
             elementSelector: static o => new Entity
             {
                 o.LongName_______________________,
-                o.LongName_______________________
+                o.LongName_______________________,
             }
         );
 
         this.GroupBy_____________(
             keySelector: static o => new Entity
             {
                 o.LongName_______________________,
-                o.LongName_______________________
+                o.LongName_______________________,
             },
             resultSelector: static o => new Entity
             {
                 o.LongName_______________________,
-                o.LongName_______________________
+                o.LongName_______________________,
             }
         );
     }

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/ArrayCreationExpressions.test

@@ -17,6 +17,6 @@ class ClassName
     private static readonly char[] initializerIndents = new char[]
     {
         Path.DirectorySeparatorChar,
-        Path.AltDirectorySeparatorChar
+        Path.AltDirectorySeparatorChar,
     };
 }

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/CollectionExpressions.test

@@ -9,14 +9,14 @@ string[] c =
     "________________________",
     "________________________",
     "________________________",
-    "________________________"
+    "________________________",
 ];
 
 int[][] d =
 [
     [1, 2, 3],
     [4, 5, 6],
-    [7, 8, 9]
+    [7, 8, 9],
 ];
 
 var a = new A { B = [1, 2, 3] };
@@ -33,7 +33,7 @@ items.AddRange(
         "which span multiple lines",
         "are added here",
         "and something bad",
-        "happens"
+        "happens",
     ]
 );
 
@@ -43,15 +43,15 @@ someObject = new SomeObject
     Property2 =
     [
         LongValue________________________________________________,
-        LongValue________________________________________________
+        LongValue________________________________________________,
     ],
-    Property3 = "three"
+    Property3 = "three",
 };
 
 someValue =
 [
     LongValue________________________________________________,
-    LongValue________________________________________________
+    LongValue________________________________________________,
 ];
 
 CallMethod(parameter1, parameterName: [1, 2]);
@@ -61,7 +61,7 @@ CallMethod(
     parameterName:
     [
         LongValue________________________________________________,
-        LongValue________________________________________________
+        LongValue________________________________________________,
     ]
 );
 
@@ -116,7 +116,7 @@ class MyClass
                 ArgConstants.NoInteractivity,
                 ArgConstants.UseProgramMain,
                 ArgConstants.NoHttps,
-                ArgConstants.Empty
+                ArgConstants.Empty,
             ],
         ];
 
@@ -138,7 +138,7 @@ class MyClass
             DayOfWeek.Wednesday,
             DayOfWeek.Thursday,
             DayOfWeek.Friday,
-            DayOfWeek.Saturday
+            DayOfWeek.Saturday,
         ];
 }
 

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/EnumDeclarationComments.expected.test

@@ -17,5 +17,5 @@ public enum SubCode
     DoNotKeepLine,
 
     [ForceLine]
-    ForceLine
+    ForceLine,
 }

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/EnumDeclarationComments.test

@@ -14,5 +14,5 @@ public enum SubCode
 
     DoNotKeepLine,
     [ForceLine]
-    ForceLine
+    ForceLine,
 }

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/EnumDeclarations.test

@@ -2,12 +2,34 @@ enum AnEnum
 {
     One,
     Two,
-    Three
+    Three,
 }
 
 public enum E
+{
+    A,
+    B = A,
+    C = 2 + A,
+}
+
+public enum EnumWithDirective
 {
     A,
     B = A,
     C = 2 + A
+#if DEBUG
+    ,
+    D = 4,
+#endif
+}
+
+public enum EnumWithDirective2
+{
+    A,
+    B = A,
+    C = 2 + A,
+#if DEBUG
+    D = 4,
+#endif
+    E = 5,
 }

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/FieldDeclarations.test

@@ -20,7 +20,7 @@ public class ClassName
     )
     {
         Property1 = 1,
-        Property2 = 2
+        Property2 = 2,
     };
 
     private LotsOfParametersToCauseBreaking ShortFieldName = new LotsOfParametersToCauseBreaking(
@@ -44,7 +44,7 @@ public class ClassName
         Property2 = false,
         Property3 = false,
         Property4 = false,
-        Property5 = false
+        Property5 = false,
     };
 
     // leading comments

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/FileEncoding_UTF8.test

@@ -6,5 +6,5 @@ public class ClassName
 public enum MeetingLocation
 {
     Café,
-    Restaurant
+    Restaurant,
 }

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/FileEncoding_UTF8BOM.test

@@ -6,5 +6,5 @@
 public enum MeetingLocation
 {
     Café,
-    Restaurant
+    Restaurant,
 }

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/ImplicitArrayCreationExpressions.test

@@ -5,7 +5,7 @@ class ClassName
     int[,] array = new[,]
     {
         { 1, 2 },
-        { 3, 4 }
+        { 3, 4 },
     };
 
     private string[] SomeArray = new[]
@@ -25,7 +25,7 @@ class ClassName
         {
             "someLongValue",
             "anotherLongValue",
-            "yetAnotherLongValue"
+            "yetAnotherLongValue",
         };
 
         return TheArrayInHereShouldAlsoNotBreak(

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/ImplicitElementAccesses.test

@@ -5,6 +5,6 @@ class ClassName
     Dictionary<int, string> dictionary = new Dictionary<int, string>
     {
         [1] = "one",
-        [2] = "two_______________________"
+        [2] = "two_______________________",
     };
 }