🐛 Ensure that the default of a list argument is used correctly

tests/test_types.py

@@ -31,7 +31,21 @@ def hello_no_choices(
 
 
 @app.command()
-def hello_all(names: list[str] = typer.Argument(["World"], envvar="NAMES")) -> None:
+def hello_all_options(name: list[str] = typer.Option(["World"])) -> None:
+    for n in name:
+        print(f"Hello {n}!")
+
+
+@app.command()
+def hello_all_args(names: list[str] = typer.Argument(["World"])) -> None:
+    for name in names:
+        print(f"Hello {name}!")
+
+
+@app.command()
+def hello_all_envvar(
+    names: list[str] = typer.Argument(["World"], envvar="NAMES"),
+) -> None:
     for name in names:
         print(f"Hello {name}!")
 
@@ -100,10 +114,40 @@ def test_enum_choice_missing_message() -> None:
     assert "morty" in result.output
 
 
+def test_list() -> None:
+    result = runner.invoke(
+        app, ["hello-all-options", "--name", "Rick", "--name", "Morty"]
+    )
+    assert result.exit_code == 0
+    assert "Hello World!" not in result.output
+    assert "Hello Rick!" in result.output
+    assert "Hello Morty!" in result.output
+
+    result = runner.invoke(app, ["hello-all-args", "Rick", "Morty"])
+    assert result.exit_code == 0
+    assert "Hello World!" not in result.output
+    assert "Hello Rick!" in result.output
+    assert "Hello Morty!" in result.output
+
+
+def test_list_empty() -> None:
+    result = runner.invoke(app, ["hello-all-args"])
+    assert result.exit_code == 0
+    assert "Hello World!" in result.output
+
+    result = runner.invoke(app, ["hello-all-options"])
+    assert result.exit_code == 0
+    assert "Hello World!" in result.output
+
+    result = runner.invoke(app, ["hello-all-envvar"])
+    assert result.exit_code == 0
+    assert "Hello World!" in result.output
+
+
 def test_split_envvar_value(monkeypatch) -> None:
     # This will use split_envvar_value to produce two strings from the envvar
     monkeypatch.setenv("NAMES", "Rick   Morty")
-    result = runner.invoke(app, ["hello-all"])
+    result = runner.invoke(app, ["hello-all-envvar"])
     assert result.exit_code == 0
     assert "Hello Rick!" in result.output
     assert "Hello Morty!" in result.output

typer/_click/parser.py

@@ -187,9 +187,9 @@ def process(
                     f"Argument {self.dest!r} takes {self.nargs} values."
                 )
 
-        if self.nargs == -1 and self.obj.envvar is not None and value == ():
-            # Replace empty tuple with None so that a value from the
-            # environment may be tried.
+        if self.nargs == -1 and value == ():
+            # Replace empty tuple with None so regular default resolution
+            # (env var, default map, and parameter default) can be tried.
             value = None
 
         state.opts[self.dest] = value  # type: ignore