use vulture hook (#45173)

Author: MarcoGorelli

.pre-commit-config.yaml

@@ -8,6 +8,13 @@ repos:
     hooks:
     -   id: absolufy-imports
         files: ^pandas/
+-   repo: https://github.com/jendrikseipp/vulture
+    rev: 'v2.3'
+    hooks:
+      - id: vulture
+        entry: python scripts/run_vulture.py
+        pass_filenames: true
+        require_serial: false
 -   repo: https://github.com/python/black
     rev: 21.12b0
     hooks:

pandas/tests/frame/test_constructors.py

@@ -1285,8 +1285,7 @@ def test_constructor_empty_list(self):
 
         # Empty generator: list(empty_gen()) == []
         def empty_gen():
-            return
-            yield
+            yield from ()
 
         df = DataFrame(empty_gen(), columns=["A", "B"])
         tm.assert_frame_equal(df, expected)

scripts/run_vulture.py

@@ -0,0 +1,21 @@
+"""Look for unreachable code."""
+
+import argparse
+import sys
+
+from vulture import Vulture
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument("files", nargs="*")
+    args = parser.parse_args()
+
+    v = Vulture()
+    v.scavenge(args.files)
+    ret = 0
+    for item in v.get_unused_code(min_confidence=100):
+        if item.typ == "unreachable_code":
+            print(item.get_report())
+            ret = 1
+
+    sys.exit(ret)