Fix issue where the open brace node includes leading newline (#11908)

Fixes one of the reported issues in
https://developercommunity.visualstudio.com/t/Format-Document-in-Razor-pages-no-longer/10903159
Fixes https://devdiv.visualstudio.com/DevDiv/_workitems/edit/2471065

Author: davidwengier

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Extensions/TextLineExtensions.cs

@@ -2,15 +2,16 @@
 // Licensed under the MIT license. See License.txt in the project root for license information.
 
 using Microsoft.AspNetCore.Razor;
-using Microsoft.CodeAnalysis.Razor;
 
 namespace Microsoft.CodeAnalysis.Text;
 
 internal static class TextLineExtensions
 {
     public static string GetLeadingWhitespace(this TextLine line)
     {
-        return line.ToString().GetLeadingWhitespace();
+        return line.GetFirstNonWhitespaceOffset() is int offset
+            ? line.Text.AssumeNotNull().ToString(TextSpan.FromBounds(line.Start, line.Start + offset))
+            : string.Empty;
     }
 
     public static int GetIndentationSize(this TextLine line, long tabSize)

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Formatting/Passes/RazorFormattingPass.cs

@@ -3,7 +3,6 @@
 
 using System.Collections.Generic;
 using System.Collections.Immutable;
-using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Threading;
@@ -419,8 +418,15 @@ private bool FormatBlock(FormattingContext context, RazorSourceDocument source,
             {
                 var openBraceLineNumber = openBraceNode.GetLinePositionSpan(source).Start.Line;
                 var openBraceLine = source.Text.Lines[openBraceLineNumber];
-                Debug.Assert(openBraceLine.GetFirstNonWhitespacePosition().HasValue);
-                additionalIndentation = source.Text.GetSubTextString(TextSpan.FromBounds(openBraceLine.Start, openBraceLine.GetFirstNonWhitespacePosition().GetValueOrDefault()));
+
+                // The open brace node might actually start with a newline on the line before, which could be blank,
+                // so make sure we find some actual content.
+                while (!openBraceLine.GetFirstNonWhitespacePosition().HasValue)
+                {
+                    openBraceLine = source.Text.Lines[++openBraceLineNumber];
+                }
+
+                additionalIndentation = openBraceLine.GetLeadingWhitespace();
             }
         }
 

src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/DocumentFormattingTest.cs

@@ -1770,6 +1770,71 @@ await RunFormattingTestAsync(
                     """);
     }
 
+    [FormattingTestFact]
+    [WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/2471065")]
+    public Task MultipleHtmlElementsInCSharpCode()
+        => RunFormattingTestAsync(
+            input: """
+                <div class="p-3 pb-0" style="min-height:24rem;">
+
+                @if (productsForExport != null)
+                {
+                <label class="section-label">
+                @(!showResult ? "some label" : "another label")
+                </label>
+
+                <div class="row">
+                <div class="col">
+                @if (!showResult)
+                {
+                <label>
+                <input type="checkbox" class="me-2 mt-1" />
+                <span>some label</span>
+                </label>
+                }
+                </div>
+
+                </div>
+                }
+
+                </div>
+
+                @code {
+                bool showResult = false;
+                object? productsForExport = null;
+                }
+                """,
+            expected: """
+                <div class="p-3 pb-0" style="min-height:24rem;">
+
+                    @if (productsForExport != null)
+                    {
+                        <label class="section-label">
+                            @(!showResult ? "some label" : "another label")
+                        </label>
+
+                        <div class="row">
+                            <div class="col">
+                                @if (!showResult)
+                                {
+                                    <label>
+                                        <input type="checkbox" class="me-2 mt-1" />
+                                        <span>some label</span>
+                                    </label>
+                                }
+                            </div>
+
+                        </div>
+                    }
+
+                </div>
+
+                @code {
+                    bool showResult = false;
+                    object? productsForExport = null;
+                }
+                """);
+
     [FormattingTestFact]
     [WorkItem("https://github.com/dotnet/aspnetcore/issues/29645")]
     public async Task FormatHtmlInIf_Range()