Fix formatting error when Roslyn adds an extra blank line

[davidwengier]

We supported when blank lines were added, but only between non-blank lines, not when the number of blank lines expanded. Also needed tab indentation to repro this one, so probably why it wasn't found originally.

Fixes https://devdiv.visualstudio.com/DevDiv/_workitems/edit/3041882

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[Copilot]

Pull request overview

This PR updates Razor’s formatting line-mapping logic to correctly preserve cases where the Roslyn formatter expands the number of blank lines (not just inserts a single blank line between non-blank lines), and adds regression coverage (both unit-level and formatting-log-based) for the scenario.

Changes:

• Update FormattingUtilities.GetOriginalDocumentChangesFromLineInfo to consume multiple inserted blank lines and handle “blank line expansion” cases while keeping original/formatted line indices synchronized.
• Add a focused regression test covering incomplete object creation formatting with tabs vs spaces.
• Add a new formatting-log test case + captured inputs/options to ensure the real-world scenario remains covered.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Razor/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Formatting/FormattingUtilities.cs	Extends line-mapping to handle multiple inserted blank lines and blank-line expansion cases.
src/Razor/src/Razor/test/Microsoft.CodeAnalysis.Razor.CohostingShared.UnitTests/Formatting/DocumentFormattingTest.cs	Adds regression tests for the repro (tabs) and a control case (spaces).
src/Razor/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.UnitTests/Cohost/Formatting/FormattingLogTest.cs	Adds a new formatting-log-driven test entrypoint for the captured scenario.
src/Razor/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.UnitTests/TestFiles/FormattingLog/BoatsSectionRange092858221/InitialDocument.txt	Captured initial document for the formatting log scenario.
src/Razor/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.UnitTests/TestFiles/FormattingLog/BoatsSectionRange092858221/Options.json	Captured formatting options (notably tabs) for the scenario.
src/Razor/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.UnitTests/TestFiles/FormattingLog/BoatsSectionRange092858221/Range.json	Captured formatting range for the scenario.
src/Razor/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.UnitTests/TestFiles/FormattingLog/BoatsSectionRange092858221/HtmlChanges.json	Captured HTML edits that preceded formatting in the scenario.
src/Razor/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.UnitTests/TestFiles/FormattingLog/BoatsSectionRange092858221/FileKind.json	Captured Razor file kind for the scenario.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

Suppressed comments (1)

src/Razor/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Formatting/FormattingUtilities.cs:376

• The comment says we should only treat this as a blank-line insertion when the next original line isn't blank, but the current check uses nextOriginalLine.Span.Length != 0, which treats whitespace-only lines (e.g. indentation-only blank lines) as non-blank. That can cause us to incorrectly interpret an aligned blank line as an insertion and add extra newlines. Use GetFirstNonWhitespaceOffset() (as the new aligned-blank logic below does) to consistently detect non-blank lines.

                    while (iFormatted + 1 < formattedText.Lines.Count &&
                        formattedText.Lines[iFormatted + 1].Span.Length == 0 &&
                        iOriginal + 1 < originalText.Lines.Count &&
                        originalText.Lines[iOriginal + 1] is { } nextOriginalLine &&
                        nextOriginalLine.Span.Length != 0)

[davidwengier]

@chsienki needs re-approval after fixing conflicts and adding WorkItem attributes. TYVM