fix whitespace sensitiveness, add more tests

src/fsharp/service/ServiceUntypedParse.fs

@@ -1306,7 +1306,7 @@ module UntypedParseImpl =
                       let g = m.Groups.["attribute"]
                       let col = pos.Column - g.Index
                       if col >= 0 && col < g.Length then
-                          let str = g.Value.Substring(0, col) // cut other rhs attributes
+                          let str = g.Value.Substring(0, col).TrimStart() // cut other rhs attributes
                           let str = cutLeadingAttributes str
                           if isLongIdent str then
                               Some CompletionContext.AttributeApplication
@@ -1317,11 +1317,11 @@ module UntypedParseImpl =
                 match lineStr.LastIndexOf "[<" with
                 | -1 -> None
                 | openParenIndex when pos.Column >= openParenIndex + 2 -> 
-                    let str = lineStr.[openParenIndex + 2..pos.Column - 1]
+                    let str = lineStr.[openParenIndex + 2..pos.Column - 1].TrimStart()
                     let str = cutLeadingAttributes str
                     if isLongIdent str then
                         Some CompletionContext.AttributeApplication
-                    else None 
+                    else None
                 | _ -> None)
 
     /// Check if we are at an "open" declaration

tests/service/ServiceUntypedParseTests.fs

@@ -60,6 +60,24 @@ type T =
 """
     => Some CompletionContext.AttributeApplication
 
+[<Test>]
+let ``AttributeApplication completion context at [< |``() =
+    """
+[< (* marker *)
+type T =
+    { F: int }
+"""
+    => Some CompletionContext.AttributeApplication
+
+[<Test>]
+let ``AttributeApplication completion context at [<AnAttribute;|``() =
+    """
+[<AnAttribute;(* marker *)
+type T =
+    { F: int }
+"""
+    => Some CompletionContext.AttributeApplication
+
 [<Test>]
 let ``AttributeApplication completion context at [<AnAttribute; |``() =
     """
@@ -78,6 +96,15 @@ type T =
 """
     => Some CompletionContext.AttributeApplication
 
+[<Test>]
+let ``AttributeApplication completion context at [<AnAttribute>][< |``() =
+    """
+[<AnAttribute>][< (* marker *)
+type T =
+    { F: int }
+"""
+    => Some CompletionContext.AttributeApplication
+
 [<Test>]
 let ``No AttributeApplication completion context at [<AnAttribute(|``() =
     """
@@ -87,6 +114,15 @@ type T =
 """
     => None
 
+[<Test>]
+let ``No AttributeApplication completion context at [<AnAttribute( |``() =
+    """
+[<AnAttribute( (* marker *)
+type T =
+    { F: int }
+"""
+    => None
+
 [<Test>]
 let ``No AttributeApplication completion context at [<AnAttribute>][<AnAttribute(|``() =
     """
@@ -116,6 +152,15 @@ type T =
 """
     => Some CompletionContext.AttributeApplication
 
+[<Test>]
+let ``AttributeApplication completion context at [< |>]``() =
+    """
+[< (* marker *)>]
+type T =
+    { F: int }
+"""
+    => Some CompletionContext.AttributeApplication
+
 [<Test>]
 let ``AttributeApplication completion context at [<AnAttribute>][<|>]``() =
     """
@@ -126,14 +171,32 @@ type T =
     => Some CompletionContext.AttributeApplication
 
 [<Test>]
-let ``AttributeApplication completion context at [<AnAttribute; | >]``() =
+let ``AttributeApplication completion context at [<AnAttribute>][< |>]``() =
+    """
+[<AnAttribute>][< (* marker *)>]
+type T =
+    { F: int }
+"""
+    => Some CompletionContext.AttributeApplication
+
+[<Test>]
+let ``AttributeApplication completion context at [<AnAttribute;|>]``() =
     """
 [<AnAttribute;(* marker *)>]
 type T =
     { F: int }
 """
     => Some CompletionContext.AttributeApplication
 
+[<Test>]
+let ``AttributeApplication completion context at [<AnAttribute; | >]``() =
+    """
+[<AnAttribute; (* marker *) >]
+type T =
+    { F: int }
+"""
+    => Some CompletionContext.AttributeApplication
+
 [<Test>]
 let ``AttributeApplication completion context at [<AnAttribute>][<AnAttribute; | >]``() =
     """
@@ -170,6 +233,15 @@ type T =
 """
     => None
 
+[<Test>]
+let ``No AttributeApplication completion context at [<AnAttribute; AnAttribute( | >]``() =
+    """
+[<AnAttribute; AnAttribute( (* marker *)>]
+type T =
+    { F: int }
+"""
+    => None
+
 [<Test>]
 let ``No AttributeApplication completion context at [<AnAttribute>][<AnAttribute; AnAttribute(| >]``() =
     """