Basic match statement support (#291)

CHANGELOG.md

@@ -1,3 +1,5 @@
+* Basic `match` statement support (kreathon, #276).
+
 # 2.5 (2022-07-03)
 
 * Mark imports in `__all__` as used (kreathon, #172, #282).

tests/test_scavenging.py

@@ -1,5 +1,7 @@
 import sys
 
+import pytest
+
 from . import check, v
 
 assert v  # Silence pyflakes.
@@ -759,3 +761,102 @@ def foo(a, b, c, d=3):
     check(v.used_names, ["foo", "a", "b", "c", "d"])
     check(v.unused_vars, [])
     check(v.unused_funcs, [])
+
+
+@pytest.mark.skipif(
+    sys.version_info < (3, 10), reason="requires python3.10 or higher"
+)
+def test_match_class_simple(v):
+    v.scan(
+        """\
+from dataclasses import dataclass
+
+
+@dataclass
+class X:
+    a: int
+    b: int
+    c: int
+    u: int
+
+x = input()
+
+match x:
+    case X(a=0):
+        print("a")
+    case X(b=0, c=0):
+        print("b c")
+"""
+    )
+    check(v.defined_classes, ["X"])
+    check(v.defined_vars, ["a", "b", "c", "u", "x"])
+
+    check(v.unused_classes, [])
+    check(v.unused_vars, ["u"])
+
+
+@pytest.mark.skipif(
+    sys.version_info < (3, 10), reason="requires python3.10 or higher"
+)
+def test_match_class_embedded(v):
+    v.scan(
+        """\
+from dataclasses import dataclass
+
+
+@dataclass
+class X:
+    a: int
+    b: int
+    c: int
+    d: int
+    e: int
+    u: int
+
+x = input()
+
+match x:
+    case X(a=1) | X(b=0):
+        print("Or")
+    case [X(c=1), X(d=0)]:
+        print("Sequence")
+    case {"k": X(e=1)}:
+        print("Mapping")
+"""
+    )
+    check(v.defined_classes, ["X"])
+    check(v.defined_vars, ["a", "b", "c", "d", "e", "u", "x"])
+
+    check(v.unused_classes, [])
+    check(v.unused_vars, ["u"])
+
+
+@pytest.mark.skipif(
+    sys.version_info < (3, 10), reason="requires python3.10 or higher"
+)
+def test_match_enum(v):
+    v.scan(
+        """\
+from enum import Enum
+
+
+class Color(Enum):
+    RED = 0
+    YELLOW = 1
+    GREEN = 2
+    BLUE = 3
+
+color = input()
+
+match color:
+    case Color.RED:
+        print("Real danger!")
+    case Color.YELLOW | Color.GREEN:
+        print("No danger!")
+"""
+    )
+    check(v.defined_classes, ["Color"])
+    check(v.defined_vars, ["RED", "YELLOW", "GREEN", "BLUE", "color"])
+
+    check(v.unused_classes, [])
+    check(v.unused_vars, ["BLUE"])

vulture/core.py

@@ -635,6 +635,10 @@ def visit_Assign(self, node):
     def visit_While(self, node):
         self._handle_conditional_node(node, "while")
 
+    def visit_MatchClass(self, node):
+        for kwd_attr in node.kwd_attrs:
+            self.used_names.add(kwd_attr)
+
     def visit(self, node):
         method = "visit_" + node.__class__.__name__
         visitor = getattr(self, method, None)

vulture/whitelists/ast_whitelist.py

@@ -39,6 +39,7 @@
 whitelist_node_visitor.visit_Lambda
 whitelist_node_visitor.visit_List
 whitelist_node_visitor.visit_ListComp
+whitelist_node_visitor.visit_MatchClass
 whitelist_node_visitor.visit_Module
 whitelist_node_visitor.visit_Name
 whitelist_node_visitor.visit_NameConstant