Fix default values of multiple options with optional values

CHANGES.rst

@@ -18,6 +18,8 @@ Unreleased
     :issue:`1969`
 -   Fix shell completion for arguments that start with a forward slash
     such as absolute file paths. :issue:`1929`
+-   Fix default values of multiple options with optional values.
+    :issue:`2001`
 
 
 Version 8.0.1

src/click/core.py

@@ -2857,6 +2857,16 @@ def consume_value(
     ) -> t.Tuple[t.Any, ParameterSource]:
         value, source = super().consume_value(ctx, opts)
 
+        if self.multiple:
+            value = [self._consume_single_value(ctx, v, source)[0] for v in value]
+        else:
+            value, source = self._consume_single_value(ctx, value, source)
+
+        return value, source
+
+    def _consume_single_value(
+        self, ctx: Context, value: t.Any, source: ParameterSource
+    ) -> t.Tuple[t.Any, ParameterSource]:
         # The parser will emit a sentinel value if the option can be
         # given as a flag without a value. This is different from None
         # to distinguish from the flag not being given at all.

tests/test_options.py

@@ -769,6 +769,61 @@ def cli(opt, a, b):
     assert result.return_value == expect
 
 
+@pytest.mark.parametrize(
+    ("args", "expect"),
+    [
+        (None, ((), None, ())),
+        (["--opt"], (("flag",), None, ())),
+        (["--opt", "-a", 42], (("flag",), "42", ())),
+        (["--opt", "test", "-a", 42], (("test",), "42", ())),
+        (["--opt=test", "-a", 42], (("test",), "42", ())),
+        (["-o"], (("flag",), None, ())),
+        (["-o", "-a", 42], (("flag",), "42", ())),
+        (["-o", "test", "-a", 42], (("test",), "42", ())),
+        (["-otest", "-a", 42], (("test",), "42", ())),
+        (["a", "b", "c"], ((), None, ("a", "b", "c"))),
+        (["--opt", "a", "b", "c"], (("a",), None, ("b", "c"))),
+        (["--opt", "test"], (("test",), None, ())),
+        (["-otest", "a", "b", "c"], (("test",), None, ("a", "b", "c"))),
+        (["--opt=test", "a", "b", "c"], (("test",), None, ("a", "b", "c"))),
+        (
+            ["--opt", "--opt", "--opt", "-a", 42],
+            (
+                (
+                    "flag",
+                    "flag",
+                    "flag",
+                ),
+                "42",
+                (),
+            ),
+        ),
+        (
+            ["--opt", "--opt", "test", "--opt", "-a", 42],
+            (
+                (
+                    "flag",
+                    "test",
+                    "flag",
+                ),
+                "42",
+                (),
+            ),
+        ),
+    ],
+)
+def test_multiple_option_with_optional_value(runner, args, expect):
+    @click.command()
+    @click.option("-o", "--opt", is_flag=False, flag_value="flag", multiple=True)
+    @click.option("-a")
+    @click.argument("b", nargs=-1)
+    def cli(opt, a, b):
+        return opt, a, b
+
+    result = runner.invoke(cli, args, standalone_mode=False, catch_exceptions=False)
+    assert result.return_value == expect
+
+
 def test_type_from_flag_value():
     param = click.Option(["-a", "x"], default=True, flag_value=4)
     assert param.type is click.INT