Formatting: force a space after attribute on parameter (#42466)

src/Workspaces/CSharpTest/Formatting/FormattingTests.cs

@@ -4435,7 +4435,7 @@ void AddClass(string name,[OptionalAttribute]    object position,[OptionalAttrib
 
             var expected = @"class Program
 {
-    void AddClass(string name, [OptionalAttribute]    object position, [OptionalAttribute]    object bases)
+    void AddClass(string name, [OptionalAttribute] object position, [OptionalAttribute] object bases)
     {
     }
 }";
@@ -9555,5 +9555,45 @@ class C
     };
 }".Replace(" ", "\u00A0"));
         }
+
+        [Fact, WorkItem(41022, "https://github.com/dotnet/roslyn/issues/41022")]
+        [Trait(Traits.Feature, Traits.Features.Formatting)]
+        public async Task SpacingAfterAttribute()
+        {
+            var code = @"class C
+{
+    void M([My]string?[]?[] x)
+    {
+    }
+}";
+            var expectedCode = @"class C
+{
+    void M([My] string?[]?[] x)
+    {
+    }
+}";
+
+            await AssertFormatAsync(expectedCode, code);
+        }
+
+        [Fact, WorkItem(41022, "https://github.com/dotnet/roslyn/issues/41022")]
+        [Trait(Traits.Feature, Traits.Features.Formatting)]
+        public async Task SpacingAfterAttribute_Multiple()
+        {
+            var code = @"class C
+{
+    void M([My][My]  int x)
+    {
+    }
+}";
+            var expectedCode = @"class C
+{
+    void M([My][My] int x)
+    {
+    }
+}";
+
+            await AssertFormatAsync(expectedCode, code);
+        }
     }
 }

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

@@ -258,6 +258,24 @@ public override AdjustSpacesOperation GetAdjustSpacesOperation(SyntaxToken previ
                 return CreateAdjustSpacesOperation(0, AdjustSpacesOption.ForceSpacesIfOnSingleLine);
             }
 
+            if (previousToken.IsKind(SyntaxKind.CloseBracketToken) &&
+                previousToken.Parent.IsKind(SyntaxKind.AttributeList) &&
+                previousToken.Parent.IsParentKind(SyntaxKind.Parameter))
+            {
+                if (currentToken.IsKind(SyntaxKind.OpenBracketToken))
+                {
+                    // multiple attribute on parameter stick together
+                    // void M([...][...]
+                    return CreateAdjustSpacesOperation(0, AdjustSpacesOption.ForceSpacesIfOnSingleLine);
+                }
+                else
+                {
+                    // attribute is spaced from parameter type
+                    // void M([...] int
+                    return CreateAdjustSpacesOperation(1, AdjustSpacesOption.ForceSpacesIfOnSingleLine);
+                }
+            }
+
             // extension method on tuple type
             // M(this (
             if (currentToken.Kind() == SyntaxKind.OpenParenToken &&