From 3de42a978a9abf014ee4b00b2492d8ee5fb6fd2d Mon Sep 17 00:00:00 2001
From: Darren Burns <darrenburns@users.noreply.github.com>
Date: Sun, 11 Aug 2024 21:16:22 +0100
Subject: [PATCH] Input validators crash fix (#4868)

* Fix crash when using validate_on with list

* Ensure tests cover crash scenario of validate_on not being a set

* Update CHANGELOG
---
 CHANGELOG.md                         | 4 ++++
 src/textual/widgets/_input.py        | 4 ++--
 tests/input/test_input_validation.py | 7 ++++---
 3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 45262df670..a1d89d071c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Added `tooltip` to Binding https://github.com/Textualize/textual/pull/4859
 
+### Fixed
+
+- Fix crash when `validate_on` value isn't a set https://github.com/Textualize/textual/pull/4868
+
 ## [0.76.0]
 
 ### Changed
diff --git a/src/textual/widgets/_input.py b/src/textual/widgets/_input.py
index 77ec211584..67743b94aa 100644
--- a/src/textual/widgets/_input.py
+++ b/src/textual/widgets/_input.py
@@ -2,7 +2,7 @@
 
 import re
 from dataclasses import dataclass
-from typing import TYPE_CHECKING, ClassVar, Iterable, cast
+from typing import TYPE_CHECKING, ClassVar, Iterable
 
 from rich.cells import cell_len, get_character_cell_size
 from rich.console import Console, ConsoleOptions, RenderableType
@@ -301,7 +301,7 @@ def __init__(
             self.validators = list(validators)
 
         self.validate_on: set[str] = (
-            (_POSSIBLE_VALIDATE_ON_VALUES & cast("set[str]", validate_on))
+            (_POSSIBLE_VALIDATE_ON_VALUES & set(validate_on))
             if validate_on is not None
             else _POSSIBLE_VALIDATE_ON_VALUES
         )
diff --git a/tests/input/test_input_validation.py b/tests/input/test_input_validation.py
index 0f70a98df8..3ea17191b5 100644
--- a/tests/input/test_input_validation.py
+++ b/tests/input/test_input_validation.py
@@ -100,10 +100,11 @@ async def test_on_blur_triggers_validation():
     "validate_on",
     [
         set(),
+        [],
         {"blur"},
-        {"submitted"},
-        {"blur", "submitted"},
-        {"fried", "garbage"},
+        ["submitted"],
+        ["blur", "submitted"],
+        ["fried", "garbage"],
     ],
 )
 async def test_validation_on_changed_should_not_happen(validate_on):