Ensure that newline is inserted after file scoped namespace declarations (#77821)

Fixes issue #67400

Author: CyrusNajmabadi

src/Analyzers/CSharp/Tests/MisplacedUsingDirectives/MisplacedUsingDirectivesTests.cs

@@ -1042,7 +1042,7 @@ namespace TestNamespace
     }
 
     [Fact]
-    public Task WhenInsidePreferred_UsingsInBoth_UsingsMoved_FileScopedNamespaec()
+    public Task WhenInsidePreferred_UsingsInBoth_UsingsMoved_FileScopedNamespace()
     {
         var testCode = """
             [|using Microsoft.CodeAnalysis;|]
@@ -1054,6 +1054,7 @@ namespace TestNamespace;
 
         var fixedTestCode = """
             namespace TestNamespace;
+
             {|Warning:using Microsoft.CodeAnalysis;|}
 
             using System;

src/Features/CSharpTest/ExtractClass/ExtractClassTests.cs

@@ -1269,6 +1269,7 @@ class Program : MyBase
             // this is my real document header
 
             namespace ConsoleApp185;
+
             using System;
             using System.Collections.Generic;
 

src/Workspaces/CSharpTest/Formatting/FormattingTests.cs

@@ -12087,6 +12087,25 @@ class C { }
             """);
     }
 
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/67400")]
+    public async Task FileScopedNamespaceNewline()
+    {
+        await AssertFormatAsync(
+            expected: """
+            namespace Some.Namespace;
+
+            public class MyClass
+            {
+            }
+            """,
+            code: """
+            namespace Some.Namespace;
+            public class MyClass
+            {
+            }
+            """);
+    }
+
     [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/56498")]
     public async Task NewInImplicitObjectCreation()
     {

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Formatting/Rules/TokenBasedFormattingRule.cs

@@ -190,7 +190,7 @@ public override AbstractFormattingRule WithOptions(SyntaxFormattingOptions optio
             return CreateAdjustNewLinesOperation(1, AdjustNewLinesOption.PreserveLines);
         }
 
-        // ; * or ; * for using directive
+        // ; * or ; * for using directive and file scoped namespace
         if (previousToken.Kind() == SyntaxKind.SemicolonToken)
         {
             return AdjustNewLinesAfterSemicolonToken(previousToken, currentToken);
@@ -225,31 +225,37 @@ MemberDeclarationSyntax or
     private AdjustNewLinesOperation AdjustNewLinesAfterSemicolonToken(
         SyntaxToken previousToken, SyntaxToken currentToken)
     {
-        // between anything that isn't a using directive, we don't touch newlines after a semicolon
-        if (previousToken.Parent is not UsingDirectiveSyntax previousUsing)
-            return CreateAdjustNewLinesOperation(0, AdjustNewLinesOption.PreserveLines);
-
-        // if the user is separating using-groups, and we're between two usings, and these
-        // usings *should* be separated, then do so (if the usings were already properly
-        // sorted).
-        if (_options.SeparateImportDirectiveGroups &&
-            currentToken.Parent is UsingDirectiveSyntax currentUsing &&
-            UsingsAndExternAliasesOrganizer.NeedsGrouping(previousUsing, currentUsing))
-        {
-            RoslynDebug.AssertNotNull(currentUsing.Parent);
-
-            var usings = GetUsings(currentUsing.Parent);
-            if (usings.IsSorted(UsingsAndExternAliasesDirectiveComparer.SystemFirstInstance) ||
-                usings.IsSorted(UsingsAndExternAliasesDirectiveComparer.NormalInstance))
+        if (previousToken.Parent is UsingDirectiveSyntax previousUsing)
+        {
+            // if the user is separating using-groups, and we're between two usings, and these
+            // usings *should* be separated, then do so (if the usings were already properly
+            // sorted).
+            if (_options.SeparateImportDirectiveGroups &&
+                currentToken.Parent is UsingDirectiveSyntax currentUsing &&
+                UsingsAndExternAliasesOrganizer.NeedsGrouping(previousUsing, currentUsing))
             {
-                // Force at least one blank line here.
-                return CreateAdjustNewLinesOperation(2, AdjustNewLinesOption.PreserveLines);
+                RoslynDebug.AssertNotNull(currentUsing.Parent);
+
+                var usings = GetUsings(currentUsing.Parent);
+                if (usings.IsSorted(UsingsAndExternAliasesDirectiveComparer.SystemFirstInstance) ||
+                    usings.IsSorted(UsingsAndExternAliasesDirectiveComparer.NormalInstance))
+                {
+                    // Force at least one blank line here.
+                    return CreateAdjustNewLinesOperation(2, AdjustNewLinesOption.PreserveLines);
+                }
             }
+
+            // For all other cases where we have a using-directive, just make sure it's followed by
+            // a new-line.
+            return CreateAdjustNewLinesOperation(1, AdjustNewLinesOption.PreserveLines);
         }
 
-        // For all other cases where we have a using-directive, just make sure it's followed by
-        // a new-line.
-        return CreateAdjustNewLinesOperation(1, AdjustNewLinesOption.PreserveLines);
+        // ensure that there is a newline after a file scoped namespace declaration
+        if (previousToken.Parent is FileScopedNamespaceDeclarationSyntax)
+            return CreateAdjustNewLinesOperation(2, AdjustNewLinesOption.PreserveLines);
+
+        // between anything that isn't a using directive or file scoped namespace declaration, we don't touch newlines after a semicolon
+        return CreateAdjustNewLinesOperation(0, AdjustNewLinesOption.PreserveLines);
     }
 
     private static SyntaxList<UsingDirectiveSyntax> GetUsings(SyntaxNode node)