Fix #3024 (comment)

Author: kdeldycke

tests/test_options.py

@@ -1653,7 +1653,48 @@ def cli(one, two):
         runner.invoke(cli, [])
 
 
-def test_custom_type_flag_value_default(runner):
+class EngineType(enum.Enum):
+    OSS = enum.auto()
+    PRO = enum.auto()
+    MAX = enum.auto()
+
+
+@pytest.mark.parametrize(
+    ("opt_params", "args", "expected"),
+    [
+        ({"flag_value": None}, [], "None"),
+        ({"flag_value": None}, ["--pro"], "None"),
+        ({"flag_value": EngineType.MAX}, [], "None"),
+        ({"flag_value": EngineType.MAX}, ["--pro"], "<EngineType.MAX: 3>"),
+        ({"default": EngineType.OSS}, [], "<EngineType.OSS: 1>"),
+        (
+            {"default": EngineType.OSS},
+            ["--pro"],
+            "Error: Option '--pro' requires an argument.\n",
+        ),
+        ({"is_flag": True, "default": EngineType.OSS}, [], "<EngineType.OSS: 1>"),
+        (
+            {"is_flag": True, "default": EngineType.OSS},
+            ["--pro"],
+            "<EngineType.OSS: 1>",
+        ),
+    ],
+)
+def test_custom_type_enum_flag_value(runner, opt_params, args, expected):
+    """A reproduction of
+    https://github.com/pallets/click/issues/3024#issuecomment-3146480714
+    """
+
+    @click.command()
+    @click.option("--pro", type=EngineType, **opt_params)
+    def scan(pro):
+        click.echo(repr(pro), nl=False)
+
+    result = runner.invoke(scan, args)
+    assert result.output == expected
+
+
+def test_custom_type_frozenset_flag_value(runner):
     """A reproduction of https://github.com/pallets/click/issues/2610"""
 
     @click.command()