Fix flag value set when is_flag=True and type is provided

CHANGES.rst

@@ -3,6 +3,8 @@
 Version 8.2.1
 -------------
 
+-   Fix flag value handling for flag options with a provided type. :issue:`2894`
+    :issue:`2897` :pr:`2930`
 
 Version 8.2.0
 -------------

src/click/core.py

@@ -2610,10 +2610,11 @@ def __init__(
             else:
                 self.default = False
 
+        if is_flag and flag_value is None:
+            flag_value = not self.default
+
         self.type: types.ParamType
         if is_flag and type is None:
-            if flag_value is None:
-                flag_value = not self.default
             # Re-guess the type from the flag value instead of the
             # default.
             self.type = types.convert_type(None, flag_value)

tests/test_options.py

@@ -1007,6 +1007,31 @@ def test_type_from_flag_value():
     assert param.type is click.INT
 
 
+@pytest.mark.parametrize(
+    ("opts", "pass_flag", "expected"),
+    [
+        pytest.param({"type": bool}, False, "False"),
+        pytest.param({"type": bool}, True, "True"),
+        pytest.param({"type": bool, "default": True}, False, "True"),
+        pytest.param({"type": bool, "default": True}, True, "False"),
+        pytest.param({"type": click.BOOL}, False, "False"),
+        pytest.param({"type": click.BOOL}, True, "True"),
+        pytest.param({"type": click.BOOL, "default": True}, False, "True"),
+        pytest.param({"type": click.BOOL, "default": True}, True, "False"),
+        pytest.param({"type": str}, False, ""),
+        pytest.param({"type": str}, True, "True"),
+    ],
+)
+def test_flag_value_is_correctly_set(runner, opts, pass_flag, expected):
+    @click.command()
+    @click.option("--foo", is_flag=True, **opts)
+    def cmd(foo):
+        click.echo(foo)
+
+    result = runner.invoke(cmd, ["--foo"] if pass_flag else [])
+    assert result.output == f"{expected}\n"
+
+
 @pytest.mark.parametrize(
     ("option", "expected"),
     [
@@ -1040,6 +1065,20 @@ def test_invalid_flag_combinations(runner, kwargs, message):
     assert message in str(e.value)
 
 
+def test_non_flag_with_non_negatable_default(runner):
+    class NonNegatable:
+        def __bool__(self):
+            raise ValueError("Cannot negate this object")
+
+    @click.command()
+    @click.option("--foo", default=NonNegatable())
+    def cmd(foo):
+        pass
+
+    result = runner.invoke(cmd)
+    assert result.exit_code == 0
+
+
 @pytest.mark.parametrize(
     ("choices", "metavars"),
     [