Add tests for action parsing. (#2112)

* Add tests for action parsing.

[skip ci]

* Fix action parsing issues.

Related issues: #2088.

* Simplify action parsing.

Turns out that we can just wrap the string that we want to parse as the arguments in '({string_here},)', as per @willmcgugan's comment in the PR review.

Related review comments: https://github.com/Textualize/textual/pull/2112\#issuecomment-1481015988

---------

Co-authored-by: Will McGugan <willmcgugan@gmail.com>

tests/test_actions.py

@@ -0,0 +1,86 @@
+from __future__ import annotations
+
+from typing import Any
+
+import pytest
+
+from textual.actions import ActionError, parse
+
+
+@pytest.mark.parametrize(
+    ("action_string", "expected_name", "expected_arguments"),
+    [
+        ("spam", "spam", ()),
+        ("hypothetical_action()", "hypothetical_action", ()),
+        ("another_action(1)", "another_action", (1,)),
+        ("foo(True, False)", "foo", (True, False)),
+        ("foo.bar.baz(3, 3.15, 'Python')", "foo.bar.baz", (3, 3.15, "Python")),
+        ("m1234.n5678(None, [1, 2])", "m1234.n5678", (None, [1, 2])),
+    ],
+)
+def test_parse_action(
+    action_string: str, expected_name: str, expected_arguments: tuple[Any]
+) -> None:
+    action_name, action_arguments = parse(action_string)
+    assert action_name == expected_name
+    assert action_arguments == expected_arguments
+
+
+@pytest.mark.parametrize(
+    ("action_string", "expected_arguments"),
+    [
+        ("f()", ()),
+        ("f(())", ((),)),
+        ("f((1, 2, 3))", ((1, 2, 3),)),
+        ("f((1, 2, 3), (1, 2, 3))", ((1, 2, 3), (1, 2, 3))),
+        ("f(((1, 2), (), None), 0)", (((1, 2), (), None), 0)),
+        ("f((((((1))))))", (1,)),
+        ("f(((((((((1, 2)))))))))", ((1, 2),)),
+        ("f((1, 2), (3, 4))", ((1, 2), (3, 4))),
+        ("f((((((1, 2), (3, 4))))))", (((1, 2), (3, 4)),)),
+    ],
+)
+def test_nested_and_convoluted_tuple_arguments(
+    action_string: str, expected_arguments: tuple[Any]
+) -> None:
+    """Test that tuple arguments are parsed correctly."""
+    _, args = parse(action_string)
+    assert args == expected_arguments
+
+
+@pytest.mark.parametrize(
+    ["action_string", "expected_arguments"],
+    [
+        ("f('')", ("",)),
+        ('f("")', ("",)),
+        ("f('''''')", ("",)),
+        ('f("""""")', ("",)),
+        ("f('(')", ("(",)),
+        ("f(')')", (")",)),  # Regression test for #2088
+        ("f('f()')", ("f()",)),
+    ],
+)
+def test_parse_action_nested_special_character_arguments(
+    action_string: str, expected_arguments: tuple[Any]
+) -> None:
+    """Test that special characters nested in strings are handled correctly.
+
+    See also: https://github.com/Textualize/textual/issues/2088
+    """
+    _, args = parse(action_string)
+    assert args == expected_arguments
+
+
+@pytest.mark.parametrize(
+    "action_string",
+    [
+        "foo(,,,,,)",
+        "bar(1 2 3 4 5)",
+        "baz.spam(Tru, Fals, in)",
+        "ham(not)",
+        "cheese((((()",
+    ],
+)
+def test_parse_action_raises_error(action_string: str) -> None:
+    with pytest.raises(ActionError):
+        parse(action_string)