Optional

src/Cli/dotnet/Commands/Run/VirtualProjectBuildingCommand.cs

@@ -1018,11 +1018,11 @@ public ProjectInstance CreateProjectInstance(ProjectCollection projectCollection
     {
         Builder.CreateProjectInstance(
             projectCollection,
-            Directives,
-            addGlobalProperties,
             ThrowingReporter,
             out var project,
-            out var evaluatedDirectives);
+            out var evaluatedDirectives,
+            Directives,
+            addGlobalProperties);
 
         Directives = evaluatedDirectives;
 

src/Microsoft.DotNet.ProjectTools/VirtualProjectBuilder.cs

@@ -122,12 +122,17 @@ public static ImmutableArray<CSharpDirective> EvaluateDirectives(
 
     public void CreateProjectInstance(
         ProjectCollection projectCollection,
-        ImmutableArray<CSharpDirective> directives,
-        Action<IDictionary<string, string>>? addGlobalProperties,
         ErrorReporter errorReporter,
         out ProjectInstance project,
-        out ImmutableArray<CSharpDirective> evaluatedDirectives)
+        out ImmutableArray<CSharpDirective> evaluatedDirectives,
+        ImmutableArray<CSharpDirective> directives = default,
+        Action<IDictionary<string, string>>? addGlobalProperties = null)
     {
+        if (directives.IsDefault)
+        {
+            directives = FileLevelDirectiveHelpers.FindDirectives(EntryPointSourceFile, reportAllErrors: false, errorReporter);
+        }
+
         project = CreateProjectInstance(projectCollection, directives, addGlobalProperties);
 
         evaluatedDirectives = EvaluateDirectives(project, directives, EntryPointSourceFile, errorReporter);