Figuring out a way to get syntax tree validation happy when we add a …

Src/CSharpier.Benchmarks/Program.cs

@@ -24,6 +24,7 @@ public void Default_SyntaxNodeComparer()
             this.code,
             false,
             false,
+            false,
             SourceCodeKind.Regular,
             CancellationToken.None
         );

Src/CSharpier.Cli/CommandLineFormatter.cs

@@ -441,6 +441,7 @@ CancellationToken cancellationToken
                 codeFormattingResult.Code,
                 codeFormattingResult.ReorderedModifiers,
                 codeFormattingResult.ReorderedUsingsWithDisabledText,
+                codeFormattingResult.MovedTrailingTrivia,
                 sourceCodeKind,
                 cancellationToken
             );

Src/CSharpier.Playground/Controllers/FormatController.cs

@@ -80,6 +80,7 @@ CancellationToken cancellationToken
             result.Code,
             result.ReorderedModifiers,
             result.ReorderedUsingsWithDisabledText,
+            result.MovedTrailingTrivia,
             sourceCodeKind,
             cancellationToken
         );

Src/CSharpier.Tests/CommandLineFormatterTests.cs

@@ -679,6 +679,26 @@ public void File_With_Reorder_Modifiers_In_If_Directive_Should_Pass_Validation(s
         result.OutputLines.First().Should().StartWith("Formatted 1 files in");
     }
 
+    [Test]
+    public void File_With_Added_Trailing_Comma_Before_Comment_Should_Pass_Validation()
+    {
+        var context = new TestContext();
+
+        var fileContents = """
+            var someObject = new SomeObject()
+            {
+                Property1 = 1,
+                Property2 = 2 // Trailing Comment
+            };
+            """;
+        context.WhenAFileExists("file1.cs", fileContents);
+
+        var result = this.Format(context);
+
+        result.ErrorOutputLines.Should().BeEmpty();
+        result.OutputLines.First().Should().StartWith("Formatted 1 files in");
+    }
+
     [TestCase(".csharpierrc")]
     [TestCase(".csharpierrc.json")]
     [TestCase(".csharpierrc.yaml")]

Src/CSharpier.Tests/FormattingTests/BaseTest.cs

@@ -63,6 +63,7 @@ protected async Task RunTest(string fileName, string fileExtension, bool useTabs
             normalizedCode,
             false,
             false,
+            false,
             SourceCodeKind.Regular,
             CancellationToken.None
         );

Src/CSharpier.Tests/Samples/Samples.cs

@@ -43,6 +43,7 @@ public static async Task RunTest(string fileName)
             result.Code,
             false,
             false,
+            false,
             SourceCodeKind.Regular,
             CancellationToken.None
         );

Src/CSharpier.Tests/SyntaxNodeComparerTests.cs

@@ -874,6 +874,30 @@ public enum Enum
         result.Should().BeEmpty();
     }
 
+    [Test]
+    public void CollectionExpression_Works_With_Adding_Comma_Before_Comment()
+    {
+        var left = """
+            var someObject = new SomeObject()
+            {
+                Property1 = 1,
+                Property2 = 2 // Trailing Comment
+            };
+            """;
+
+        var right = """
+            var someObject = new SomeObject()
+            {
+                Property1 = 1,
+                Property2 = 2, // Trailing Comment
+            };
+            """;
+
+        var result = CompareSource(left, right, movedTrailingTrivia: true);
+
+        result.Should().BeEmpty();
+    }
+
     private static void ResultShouldBe(string actual, string expected)
     {
         actual.ReplaceLineEndings().Should().Be(expected.ReplaceLineEndings());
@@ -882,14 +906,16 @@ private static void ResultShouldBe(string actual, string expected)
     private static string CompareSource(
         string left,
         string right,
-        bool reorderedUsingsWithDisabledText = false
+        bool reorderedUsingsWithDisabledText = false,
+        bool movedTrailingTrivia = false
     )
     {
         var result = new SyntaxNodeComparer(
             left,
             right,
             false,
             reorderedUsingsWithDisabledText,
+            movedTrailingTrivia,
             SourceCodeKind.Regular,
             CancellationToken.None
         ).CompareSource();

Src/CSharpier/CSharpFormatter.cs

@@ -130,6 +130,7 @@ bool TryGetCompilationFailure(out CodeFormatterResult compilationResult)
             var formattedCode = DocPrinter.DocPrinter.Print(document, printerOptions, lineEnding);
             var reorderedModifiers = formattingContext.ReorderedModifiers;
             var reorderedUsingsWithDisabledText = formattingContext.ReorderedUsingsWithDisabledText;
+            var movedTrailingTrivia = formattingContext.MovedTrailingTrivia;
 
             foreach (var symbolSet in PreprocessorSymbols.GetSets(syntaxTree))
             {
@@ -155,6 +156,7 @@ await syntaxTree.GetRootAsync(cancellationToken),
                 reorderedUsingsWithDisabledText =
                     reorderedUsingsWithDisabledText
                     || formattingContext2.ReorderedUsingsWithDisabledText;
+                movedTrailingTrivia = movedTrailingTrivia || formattingContext2.MovedTrailingTrivia;
             }
 
             return new CodeFormatterResult
@@ -166,6 +168,7 @@ await syntaxTree.GetRootAsync(cancellationToken),
                 AST = printerOptions.IncludeAST ? PrintAST(rootNode) : string.Empty,
                 ReorderedModifiers = reorderedModifiers,
                 ReorderedUsingsWithDisabledText = reorderedUsingsWithDisabledText,
+                MovedTrailingTrivia = movedTrailingTrivia,
             };
         }
         catch (InTooDeepException)

Src/CSharpier/CodeFormatterResult.cs

@@ -16,4 +16,5 @@ internal CodeFormatterResult() { }
 
     internal bool ReorderedModifiers { get; init; }
     internal bool ReorderedUsingsWithDisabledText { get; init; }
+    internal bool MovedTrailingTrivia { get; init; }
 }

Src/CSharpier/SyntaxNodeComparer.cs

@@ -10,6 +10,7 @@ internal partial class SyntaxNodeComparer
     protected SyntaxTree NewSyntaxTree { get; }
     protected bool ReorderedModifiers { get; }
     protected bool ReorderedUsingsWithDisabledText { get; }
+    protected bool MovedTrailingTrivia { get; }
 
     private static readonly CompareResult Equal = new();
 
@@ -18,6 +19,7 @@ public SyntaxNodeComparer(
         string newSourceCode,
         bool reorderedModifiers,
         bool reorderedUsingsWithDisabledText,
+        bool movedTrailingTrivia,
         SourceCodeKind sourceCodeKind,
         CancellationToken cancellationToken
     )
@@ -26,6 +28,7 @@ CancellationToken cancellationToken
         this.NewSourceCode = newSourceCode;
         this.ReorderedModifiers = reorderedModifiers;
         this.ReorderedUsingsWithDisabledText = reorderedUsingsWithDisabledText;
+        this.MovedTrailingTrivia = movedTrailingTrivia;
 
         var cSharpParseOptions = new CSharpParseOptions(
             CSharpFormatter.LanguageVersion,
@@ -274,7 +277,9 @@ originalToken.Parent is InterpolatedStringExpressionSyntax
             return result;
         }
 
-        var result2 = this.Compare(originalToken.TrailingTrivia, formattedToken.TrailingTrivia);
+        var result2 = this.MovedTrailingTrivia
+            ? Equal
+            : this.Compare(originalToken.TrailingTrivia, formattedToken.TrailingTrivia);
 
         return result2.IsInvalid ? result2 : Equal;
     }

Src/CSharpier/SyntaxPrinter/FormattingContext.cs

@@ -22,6 +22,10 @@ internal class FormattingContext
     // we also need to keep track if we move around usings with disabledText
     public bool ReorderedUsingsWithDisabledText { get; set; }
 
+    // when adding a trailing comma in front of a trailing comment it is very hard to determine how to compare
+    // that trailing comment, so just ignore all trailing trivia
+    public bool MovedTrailingTrivia { get; set; }
+
     public TrailingCommaContext? TrailingComma { get; set; }
 
     public FormattingContext WithSkipNextLeadingTrivia()

Src/CSharpier/SyntaxPrinter/Token.cs

@@ -132,6 +132,7 @@ context.TrailingComma is not null
                 )
                 {
                     docs.Add(context.TrailingComma.PrintedTrailingComma);
+                    context.MovedTrailingTrivia = true;
                     context.TrailingComma = null;
                 }