SyntaxFactory.ParseCompilationUnit drops parse options

[tmat]

The ParseOptions returned from SyntaxFactory.ParseCompilationUnit("", options: options).SyntaxTree.Options are the default parse options, not the options passed to the ParseCompilationUnit call.

Workaround:

var unit = SyntaxFactory.CompilationUnit();
unit = unit.SyntaxTree.WithRootAndOptions(unit, options).GetRoot(cancellationToken);

[bernd5]

To fix it we should simply set the tree directly. Currently we rely on ComputeSyntaxTree / CreateWithoutClone which has no reference to the options...

So ParseCompilationUnit should be changed to:

 public static CompilationUnitSyntax ParseCompilationUnit(string text, int offset = 0, CSharpParseOptions? options = null)
 {
     // note that we do not need a "consumeFullText" parameter, because parsing a compilation unit always must
     // consume input until the end-of-file
     using (var lexer = MakeLexer(text, offset, options))
     using (var parser = MakeParser(lexer))
     {
         var node = parser.ParseCompilationUnit();
         var unit = (CompilationUnitSyntax)node.CreateRed();
         if (options != null)
         {
           Debug.Assert(unit._syntaxTree == null);
           unit._syntaxTree = CSharpSyntaxTree.Create(unit, options, "", Encoding.Unicode);
         }
         return unit;
     }
 }

Another option would be to use CSharpSyntaxTree.ParseText.

[RikkiGibson]

This appears to be the root cause of #78675