Merge doc comments across multiple parts

src/EditorFeatures/CSharpTest/QuickInfo/SemanticQuickInfoSourceTests.cs

@@ -398,6 +398,25 @@ await TestAsync(markup,
             Documentation("summary for interface IGoo"));
     }
 
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/60725")]
+    public async Task TestMergedRemarks()
+    {
+        var markup =
+            """
+            /// <remarks>hello1</remarks>
+            public partial class C {
+            }
+
+            /// <remarks>hello2</remarks>
+            public partial class $$C {
+            }
+            """;
+
+        await TestAsync(markup,
+            MainDescription("class C"),
+            Remarks("hello1 hello2"));
+    }
+
     [Fact, WorkItem("http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/991466")]
     public async Task TestDocumentationInUsingDirectiveWithAlias3()
     {
@@ -516,7 +535,9 @@ void M()
 
         // SingleLine doc comment with '\r' line separators
         await TestAsync("""
-            ///<summary>Hello!            ///</summary>            class C { void M() { $$C obj; } }
+            ///<summary>Hello!
+            ///</summary>
+            class C { void M() { $$C obj; } }
             """,
             MainDescription("class C"),
             Documentation("Hello!"));
@@ -632,7 +653,12 @@ void M()
 
         // Multiline doc comment with '\r' line separators
         await TestAsync("""
-            /**            * <summary>            * Hello!            * </summary>            */            class C { void M() { $$C obj; } }
+            /**
+            * <summary>
+            * Hello!
+            * </summary>
+            */
+            class C { void M() { $$C obj; } }
             """,
             MainDescription("class C"),
             Documentation("Hello!"));

src/EditorFeatures/Test2/Workspaces/SymbolDescriptionServiceTests.vb

@@ -10,10 +10,8 @@ Imports Microsoft.CodeAnalysis.Host
 Imports Microsoft.CodeAnalysis.LanguageService
 
 Namespace Microsoft.CodeAnalysis.Editor.UnitTests.Workspaces
-
     <[UseExportProvider]>
     Public Class SymbolDescriptionServiceTests
-
         Private Shared Async Function TestAsync(languageServiceProvider As HostLanguageServices, workspace As EditorTestWorkspace, expectedDescription As String) As Task
 
             Dim solution = workspace.CurrentSolution

src/Features/CSharp/Portable/DocumentationComments/CSharpDocumentationCommentFormattingService.cs

@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-#nullable disable
-
 using System.Composition;
 using System.Diagnostics.CodeAnalysis;
 using Microsoft.CodeAnalysis.DocumentationComments;
@@ -12,11 +10,6 @@
 namespace Microsoft.CodeAnalysis.CSharp.DocumentationComments;
 
 [ExportLanguageService(typeof(IDocumentationCommentFormattingService), LanguageNames.CSharp), Shared]
-internal class CSharpDocumentationCommentFormattingService : AbstractDocumentationCommentFormattingService
-{
-    [ImportingConstructor]
-    [SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]
-    public CSharpDocumentationCommentFormattingService()
-    {
-    }
-}
+[method: ImportingConstructor]
+[method: SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]
+internal sealed class CSharpDocumentationCommentFormattingService() : AbstractDocumentationCommentFormattingService;

src/Workspaces/Core/Portable/Shared/Utilities/DocumentationComment.cs

@@ -7,8 +7,8 @@
 using System.Collections.Immutable;
 using System.Xml;
 using Microsoft.CodeAnalysis.PooledObjects;
-using XmlNames = Roslyn.Utilities.DocumentationCommentXmlNames;
 using Microsoft.CodeAnalysis.Shared.Extensions;
+using XmlNames = Roslyn.Utilities.DocumentationCommentXmlNames;
 
 namespace Microsoft.CodeAnalysis.Shared.Utilities;
 
@@ -227,89 +227,98 @@ private static string TrimEachLine(string text)
 
         private void ParseCallback(XmlReader reader)
         {
-            if (reader.NodeType == XmlNodeType.Element)
+            if (reader.NodeType != XmlNodeType.Element)
             {
-                var localName = reader.LocalName;
-                if (XmlNames.ElementEquals(localName, XmlNames.ExampleElementName) && _comment.ExampleText == null)
-                {
-                    _comment.ExampleText = TrimEachLine(reader.ReadInnerXml());
-                }
-                else if (XmlNames.ElementEquals(localName, XmlNames.SummaryElementName) && _comment.SummaryText == null)
-                {
-                    _comment.SummaryText = TrimEachLine(reader.ReadInnerXml());
-                }
-                else if (XmlNames.ElementEquals(localName, XmlNames.ReturnsElementName) && _comment.ReturnsText == null)
-                {
-                    _comment.ReturnsText = TrimEachLine(reader.ReadInnerXml());
-                }
-                else if (XmlNames.ElementEquals(localName, XmlNames.ValueElementName) && _comment.ValueText == null)
-                {
-                    _comment.ValueText = TrimEachLine(reader.ReadInnerXml());
-                }
-                else if (XmlNames.ElementEquals(localName, XmlNames.RemarksElementName) && _comment.RemarksText == null)
+                // We came across something that isn't a start element, like a block of text. Skip it.
+                reader.Read();
+                return;
+            }
+
+            var localName = reader.LocalName;
+            if (XmlNames.ElementEquals(localName, XmlNames.ExampleElementName))
+            {
+                _comment.ExampleText = InitializeValue(_comment.ExampleText, TrimEachLine(reader.ReadInnerXml()));
+            }
+            else if (XmlNames.ElementEquals(localName, XmlNames.SummaryElementName))
+            {
+                _comment.SummaryText = InitializeValue(_comment.SummaryText, TrimEachLine(reader.ReadInnerXml()));
+            }
+            else if (XmlNames.ElementEquals(localName, XmlNames.ReturnsElementName))
+            {
+                _comment.ReturnsText = InitializeValue(_comment.ReturnsText, TrimEachLine(reader.ReadInnerXml()));
+            }
+            else if (XmlNames.ElementEquals(localName, XmlNames.ValueElementName))
+            {
+                _comment.ValueText = InitializeValue(_comment.ValueText, TrimEachLine(reader.ReadInnerXml()));
+            }
+            else if (XmlNames.ElementEquals(localName, XmlNames.RemarksElementName))
+            {
+                _comment.RemarksText = InitializeValue(_comment.RemarksText, TrimEachLine(reader.ReadInnerXml()));
+            }
+            else if (XmlNames.ElementEquals(localName, XmlNames.ParameterElementName))
+            {
+                var name = reader.GetAttribute(XmlNames.NameAttributeName);
+                var paramText = reader.ReadInnerXml();
+
+                if (!string.IsNullOrWhiteSpace(name) && !_comment._parameterTexts.ContainsKey(name))
                 {
-                    _comment.RemarksText = TrimEachLine(reader.ReadInnerXml());
+                    (_parameterNamesBuilder ??= ImmutableArray.CreateBuilder<string>()).Add(name);
+                    _comment._parameterTexts.Add(name, TrimEachLine(paramText));
                 }
-                else if (XmlNames.ElementEquals(localName, XmlNames.ParameterElementName))
-                {
-                    var name = reader.GetAttribute(XmlNames.NameAttributeName);
-                    var paramText = reader.ReadInnerXml();
+            }
+            else if (XmlNames.ElementEquals(localName, XmlNames.TypeParameterElementName))
+            {
+                var name = reader.GetAttribute(XmlNames.NameAttributeName);
+                var typeParamText = reader.ReadInnerXml();
 
-                    if (!string.IsNullOrWhiteSpace(name) && !_comment._parameterTexts.ContainsKey(name))
-                    {
-                        (_parameterNamesBuilder ??= ImmutableArray.CreateBuilder<string>()).Add(name);
-                        _comment._parameterTexts.Add(name, TrimEachLine(paramText));
-                    }
-                }
-                else if (XmlNames.ElementEquals(localName, XmlNames.TypeParameterElementName))
+                if (!string.IsNullOrWhiteSpace(name) && !_comment._typeParameterTexts.ContainsKey(name))
                 {
-                    var name = reader.GetAttribute(XmlNames.NameAttributeName);
-                    var typeParamText = reader.ReadInnerXml();
-
-                    if (!string.IsNullOrWhiteSpace(name) && !_comment._typeParameterTexts.ContainsKey(name))
-                    {
-                        (_typeParameterNamesBuilder ??= ImmutableArray.CreateBuilder<string>()).Add(name);
-                        _comment._typeParameterTexts.Add(name, TrimEachLine(typeParamText));
-                    }
+                    (_typeParameterNamesBuilder ??= ImmutableArray.CreateBuilder<string>()).Add(name);
+                    _comment._typeParameterTexts.Add(name, TrimEachLine(typeParamText));
                 }
-                else if (XmlNames.ElementEquals(localName, XmlNames.ExceptionElementName))
-                {
-                    var type = reader.GetAttribute(XmlNames.CrefAttributeName);
-                    var exceptionText = reader.ReadInnerXml();
-
-                    if (!string.IsNullOrWhiteSpace(type))
-                    {
-                        if (_exceptionTextBuilders == null || !_exceptionTextBuilders.ContainsKey(type))
-                        {
-                            (_exceptionTypesBuilder ??= ImmutableArray.CreateBuilder<string>()).Add(type);
-                            (_exceptionTextBuilders ??= []).Add(type, ImmutableArray.CreateBuilder<string>());
-                        }
+            }
+            else if (XmlNames.ElementEquals(localName, XmlNames.ExceptionElementName))
+            {
+                var type = reader.GetAttribute(XmlNames.CrefAttributeName);
+                var exceptionText = reader.ReadInnerXml();
 
-                        _exceptionTextBuilders[type].Add(exceptionText);
-                    }
-                }
-                else if (XmlNames.ElementEquals(localName, XmlNames.CompletionListElementName))
+                if (!string.IsNullOrWhiteSpace(type))
                 {
-                    var cref = reader.GetAttribute(XmlNames.CrefAttributeName);
-                    if (!string.IsNullOrWhiteSpace(cref))
+                    if (_exceptionTextBuilders == null || !_exceptionTextBuilders.ContainsKey(type))
                     {
-                        _comment.CompletionListCref = cref;
+                        (_exceptionTypesBuilder ??= ImmutableArray.CreateBuilder<string>()).Add(type);
+                        (_exceptionTextBuilders ??= []).Add(type, ImmutableArray.CreateBuilder<string>());
                     }
 
-                    reader.ReadInnerXml();
+                    _exceptionTextBuilders[type].Add(exceptionText);
                 }
-                else
+            }
+            else if (XmlNames.ElementEquals(localName, XmlNames.CompletionListElementName))
+            {
+                var cref = reader.GetAttribute(XmlNames.CrefAttributeName);
+                if (!string.IsNullOrWhiteSpace(cref))
                 {
-                    // This is an element we don't handle. Skip it.
-                    reader.Read();
+                    _comment.CompletionListCref = cref;
                 }
+
+                reader.ReadInnerXml();
             }
             else
             {
-                // We came across something that isn't a start element, like a block of text.
-                // Skip it.
+                // This is an element we don't handle. Skip it.
                 reader.Read();
             }
+
+            return;
+
+            static string InitializeValue(string? existingValue, string newValue)
+            {
+                // The use of Environment.NewLine matches the behavior of StringBuilder.AppendLine used in multiple
+                // places in this file.
+                return existingValue is null or ""
+                    ? newValue
+                    : $"{existingValue}{Environment.NewLine}{newValue}";
+            }
         }
     }