From e49c133b484fa464449f571976ed55e4663ca27b Mon Sep 17 00:00:00 2001
From: Hadi Alqattan <alqattanhadizaki@gmail.com>
Date: Wed, 14 Oct 2020 22:27:07 +0300
Subject: [PATCH] Support implicit imports from sub-packages. (#37)

---
 docs/CHANGELOG.md       |  1 +
 docs/README.md          | 12 ++++++++++++
 pycln/utils/refactor.py | 19 ++++++++++++++++++-
 tests/test_refactor.py  | 18 ++++++++++++++++++
 4 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index c940134..e8d8711 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -12,6 +12,7 @@ this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ### Added
 
+- [Support implicit imports from sub-packages by @hadialqattan](https://github.com/hadialqattan/pycln/pull/36)
 - [Support semi string type hint by @hadialqattan](https://github.com/hadialqattan/pycln/pull/35)
 - [Support casting case by @hadialqattan](https://github.com/hadialqattan/pycln/pull/34)
 
diff --git a/docs/README.md b/docs/README.md
index 68a0c47..1e7d9d7 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -716,6 +716,18 @@ All bellow imports are considered as used:
       import y
   ```
 
+### Implicit Imports From Sub-Packages
+
+> Pycln can deal with implicit imports from sub-packages.
+
+For example:
+
+```python
+import os.path  # marked as used.
+
+print(os.getpid())
+```
+
 ### Import With Importlib
 
 > Not supported yet, on the roadmap:
diff --git a/pycln/utils/refactor.py b/pycln/utils/refactor.py
index e22a8bd..9ec7ace 100644
--- a/pycln/utils/refactor.py
+++ b/pycln/utils/refactor.py
@@ -246,7 +246,9 @@ def _get_used_names(
         """
         used_names: Set[str] = set()
         for alias in node.names:
-            if self._should_remove(node, alias, is_star):
+            if self._should_remove(
+                node, alias, is_star
+            ) and not self._is_partially_used(alias, is_star):
                 if not is_star:
                     self.reporter.removed_import(self._path, node, alias)
                 continue
@@ -308,6 +310,21 @@ def _expand_import_star(
             self.reporter.ignored_import(self._path, node, is_star=True)
             return node, None
 
+    def _is_partially_used(self, alias: ast.alias, is_star: bool) -> bool:
+        """Determine if the alias name partially used or not.
+
+        :param alias: an `ast.alias` node.
+        :param is_star: is it a '*' import.
+        :returns: whather the alias name partially used or not.
+        """
+        if not alias.asname and "." in alias.name:
+            names = alias.name.split(".")[1:]
+            for name in reversed(names):
+                alias.name = alias.name.rstrip("." + name)
+                if self._has_used(alias.name, is_star):
+                    return True
+        return False
+
     def _should_remove(
         self, node: Union[Import, ImportFrom], alias: ast.alias, is_star: bool
     ) -> bool:
diff --git a/tests/test_refactor.py b/tests/test_refactor.py
index 25cb735..bc71581 100644
--- a/tests/test_refactor.py
+++ b/tests/test_refactor.py
@@ -533,6 +533,24 @@ def test_expand_import_star(
         enode, is_star = self.session_maker._expand_import_star(node)
         assert (enode, is_star) == (node, expec_is_star)
 
+    @pytest.mark.parametrize(
+        "_has_used_return, name, asname, expec_val",
+        [
+            pytest.param(True, "os.path.join", None, True, id="used"),
+            pytest.param(False, "os.path.join", None, False, id="unused"),
+            pytest.param(None, "os.path.join", "asname", False, id="as alias"),
+            pytest.param(None, "os", None, False, id="single name"),
+        ],
+    )
+    @mock.patch(MOCK % "Refactor._has_used")
+    def test_is_partially_used(
+        self, _has_used, _has_used_return, name, asname, expec_val
+    ):
+        _has_used.return_value = _has_used_return
+        alias = ast.alias(name=name, asname=asname)
+        val = self.session_maker._is_partially_used(alias, False)
+        assert val == expec_val
+
     @pytest.mark.parametrize(
         "_has_used_return, _has_side_effects_return, all_, name, expec_val",
         [