Reduce noise in signatures of compiled params (#1564)

* Remove "typing." prefix from compiled signature param

* Don't print default "None" for Optional params

* Don't remove 'typing.' prefix if symbol doesn't come from typing module

* Revert "Don't print default "None" for Optional params"

This reverts commit 8db334d9bb.

* Make sure "typing." doesn't appear in the middle

* Make sure only "typing." prefix is removed and not it's entries in the middle

* Use inspect.formatannotation() to create an annotation string

* Update AUTHORS.txt

* Add test for compiled param annotation string

* Replace Optional in test with other typing facilities

in order for test to be forward-compatible with 3.9

* Add an empty string fallback for Python 2

* Move _annotation_to_str back to original position

test/test_inference/test_mixed.py

@@ -102,3 +102,14 @@ def test_signature():
 
     s, = jedi.Interpreter('some_signature', [locals()]).goto()
     assert s.docstring() == 'some_signature(*, bar=1)'
+
+
+@pytest.mark.skipif(sys.version_info[0:2] < (3, 5), reason="Typing was introduced in Python 3.5")
+def test_compiled_signature_annotation_string():
+    import typing
+    def func(x: typing.Type, y: typing.Union[typing.Type, int]): pass
+    func.__name__ = 'not_func'
+
+    s, = jedi.Interpreter('func()', [locals()]).get_signatures(1, 5)
+    assert s.params[0].description == 'param x: Type'
+    assert s.params[1].description == 'param y: Union[Type, int]'