Fix: imports used in generics and wrapped in string get removed. (#178)

docs/CHANGELOG.md

@@ -12,6 +12,7 @@ this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ### Fixed
 
+- [Imports used in generics and wrapped in string get removed by @hadialqattan](https://github.com/hadialqattan/pycln/pull/178)
 - [Setting an artificial lock to LibCST version `+0.4.0` for Python `3.6.x`; a bug introduced in LibCST `+0.4.0` that affects `PY3.6` by @hadialqattan](https://github.com/hadialqattan/pycln/pull/174)
 
 ### Added

docs/README.md

@@ -1005,6 +1005,23 @@ __all__ = ["os", "time"]
 > Not supported, also not on the
 > [roadmap](https://github.com/hadialqattan/pycln/projects/3).
 
+### Generics wrapping strings
+
+> Pycln can understand imports used in generics and wrapped in string.
+
+```python
+from typing import Generic, TypeVar
+from xxx import Baz  # marked as used.
+
+CustomType = TypeVar("CustomType")
+
+class Foo(Generic[CustomType]):
+    ...
+
+class Bar(Foo["Baz"]):  # <~
+    ...
+```
+
 ### Init file (`__init__.py`)
 
 > Pycln can not decide whether the unused imported names are useless or imported to be

pycln/utils/scan.py

@@ -299,6 +299,29 @@ def visit_FunctionDef(self, node: FunctionDefT):
     # Support `ast.AsyncFunctionDef`.
     visit_AsyncFunctionDef = visit_FunctionDef
 
+    @recursive
+    def visit_ClassDef(self, node: ast.ClassDef):
+        #: Support imports used in generics and wrapped in string:
+        #:
+        #: >>> from typing import Generic
+        #: >>> from foo import Bar
+        #: >>>
+        #: >>> class SuperClass(Generic[SomeType]):
+        #: >>>     ...
+        #: >>>
+        #: >>> class SubClass(SuperClass["Bar"])  # <~ detecting Bar.
+        #: >>>     ...
+        #:
+        #: Issue: https://github.com/hadialqattan/pycln/issues/169
+        for base in node.bases:
+            if isinstance(base, ast.Subscript):
+                if PY39_PLUS:
+                    s_val = base.slice  # type: ignore
+                else:
+                    s_val = base.slice.value  # type: ignore
+                for elt in getattr(s_val, "elts", ()) or (s_val,):
+                    self._parse_string(elt)  # type: ignore
+
     @recursive
     def visit_Assign(self, node: ast.Assign):
         # Support Python ^3.8 type comments.

tests/test_scan.py

@@ -563,6 +563,31 @@ def test_visit_AsyncFunctionDef(self, code, expec_names):
         source_stats, _ = analyzer.get_stats()
         self.assert_set_equal_or_not(source_stats.name_, expec_names)
 
+    @pytest.mark.parametrize(
+        "code, expec_names",
+        [
+            pytest.param(
+                ("class Foo(Bar):\n" "    pass"),
+                {"Bar"},
+                id="no generics",
+            ),
+            pytest.param(
+                ("class Foo(Bar['Baz']):\n" "    pass"),
+                {"Bar", "Baz"},
+                id="one generic",
+            ),
+            pytest.param(
+                ("class Foo(Bar['Baz'], Bax['Tax']):\n" "    pass"),
+                {"Bar", "Baz", "Bax", "Tax"},
+                id="many generics",
+            ),
+        ],
+    )
+    def test_visit_ClassDef(self, code, expec_names):
+        analyzer = self._get_analyzer(code)
+        source_stats, _ = analyzer.get_stats()
+        self.assert_set_equal_or_not(source_stats.name_, expec_names)
+
     @pytest.mark.parametrize(
         "code, expec_names, expec_names_to_skip",
         [