[nullsafe] A helper function to extract outer class.

Summary: To be used in the next diff.

Reviewed By: artempyanykh

Differential Revision: D21228077

fbshipit-source-id: f4220f953

infer/src/IR/JavaClassName.ml

@@ -63,6 +63,10 @@ let is_int s =
   with Failure _ -> false
 
 
+let get_outer_class_name {package; classname} =
+  String.rsplit2 classname ~on:'$' |> Option.map ~f:(fun (outer, _) -> {package; classname= outer})
+
+
 (* Strips $<int> suffixes from the class name, and return how many were stripped *)
 let strip_anonymous_suffixes_if_present classname =
   let rec strip_recursively classname nesting_level =

infer/src/IR/JavaClassName.mli

@@ -31,6 +31,10 @@ val classname : t -> string
 val is_external_via_config : t -> bool
 (** Considered external based on config flags. *)
 
+val get_outer_class_name : t -> t option
+(** If this is an inner class, return the closest outer, e.g. A$B for A$B$C. None if the class is
+    outermost *)
+
 val is_anonymous_inner_class_name : t -> bool
 (** True if it is either "classic" anonymous Java class:
     https://docs.oracle.com/javase/tutorial/java/javaOO/anonymousclasses.html, or a synthetic Java

infer/src/unit/JavaClassNameTests.ml

@@ -105,4 +105,18 @@ let test_anonymous =
        ~expected_classname:"SomeClass$NestedClass$AgainNestedClass"
 
 
-let tests = "JavaClassNameTests" >::: [test_from_string; test_anonymous]
+let test_outer =
+  "test_outer"
+  >:: fun _ ->
+  get_outer_class_name (make ~package:(Some "some.package") ~classname:"SomeClass") |> assert_none ;
+  get_outer_class_name (make ~package:(Some "some.package") ~classname:"SomeClass$NestedClass")
+  |> assert_some
+  |> assert_equal_to ~expected_package:(Some "some.package") ~expected_classname:"SomeClass" ;
+  get_outer_class_name
+    (make ~package:(Some "some.package") ~classname:"SomeClass$NestedClass$AnotherNested")
+  |> assert_some
+  |> assert_equal_to ~expected_package:(Some "some.package")
+       ~expected_classname:"SomeClass$NestedClass"
+
+
+let tests = "JavaClassNameTests" >::: [test_from_string; test_anonymous; test_outer]