Fix C# formatting for file-based app directives parsed as IgnoredDirectiveTriviaSyntax.

When the formatter touches a line like:

 #:package Newtonsoft.Json@13.0.3

Roslyn was rewriting it to:

# : package Newtonsoft.Json@13.0.3

That breaks file-based app syntax and causes downstream issues such as loss of project/file-based-app recognition and completion failures.

Root cause

File-based app directives are represented as IgnoredDirectiveTriviaSyntax, but StructuredTriviaFormattingRule did not preserve spacing for the syntax-significant token sequence:

• HashToken -> ColonToken
• ColonToken -> Content

As a result, generic punctuation spacing rules inserted spaces around : once the directive line became eligible for formatting.

Fix

Add a special-case in StructuredTriviaFormattingRule to force zero spaces for:

• # followed by :
• : followed by the directive content

inside IgnoredDirectiveTriviaSyntax.

Tests

Added formatter coverage for file-based app directives:

• unchanged formatting for a normal #:package ... directive
• regression test showing that a directive with leading whitespace is normalized to valid #:package ... form instead of # : package ...

This should also fix this vscode-csharp issue

Microsoft Reviewers: Open in CodeFlow