Update the current module when a new file is parsed (#99)

* Update the current module when a new file is parsed

FixAnnotateJson.current_module is currently a constant value, which causes bugs when pyannotate is run on a package directory.

* Add a test

pyannotate_tools/fixes/fix_annotate_json.py

@@ -169,6 +169,10 @@ def patch_imports(self, types, node):
                 touch_import(mod, name, node)
         self.needed_imports = None
 
+    def set_filename(self, filename):
+        super(FixAnnotateJson, self).set_filename(filename)
+        self._current_module = crawl_up(filename)[1]
+
     def current_module(self):
         return self._current_module
 
@@ -208,7 +212,7 @@ def max_line_drift_set(cls, max_drift):
     @classmethod
     def init_stub_json_from_data(cls, data, filename):
         cls.stub_json = data
-        cls.top_dir, cls._current_module = crawl_up(os.path.abspath(filename))
+        cls.top_dir = crawl_up(os.path.abspath(filename))[0]
 
     def init_stub_json(self):
         with open(self.__class__.stub_json_file) as f:

pyannotate_tools/fixes/tests/test_annotate_json_py3.py

@@ -6,6 +6,7 @@
 import tempfile
 import unittest
 import sys
+from mock import patch
 
 from lib2to3.tests.test_fixers import FixerTestCase
 
@@ -632,3 +633,13 @@ async def foo(x: str) -> int:
                         return 42
             """
         self.check(a, b)
+
+    @patch('pyannotate_tools.fixes.fix_annotate_json.FixAnnotateJson.set_filename')
+    def test_set_filename(self, mocked_set_filename):
+        self.filename = "/path/to/fileA.py"
+        self.unchanged("")
+        mocked_set_filename.assert_called_with("/path/to/fileA.py")
+
+        self.filename = "/path/to/fileB.py"
+        self.unchanged("")
+        mocked_set_filename.assert_called_with("/path/to/fileB.py")