From 1410648e36c19ed59b41e75833d22cdc33553dc6 Mon Sep 17 00:00:00 2001
From: Darren Burns <darrenb900@gmail.com>
Date: Tue, 18 Jan 2022 14:13:40 +0000
Subject: [PATCH] Add Styles.reset method revert internal attributes to None

---
 src/textual/css/styles.py     |  4 ++++
 src/textual/css/stylesheet.py |  2 +-
 tests/test_styles.py          | 11 +++++++++++
 3 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 tests/test_styles.py

diff --git a/src/textual/css/styles.py b/src/textual/css/styles.py
index 4e48fa95b..c324426e9 100644
--- a/src/textual/css/styles.py
+++ b/src/textual/css/styles.py
@@ -235,6 +235,10 @@ class Styles:
         else:
             return None
 
+    def reset(self) -> None:
+        for rule_name in INTERNAL_RULE_NAMES:
+            setattr(self, rule_name, None)
+
     def extract_rules(
         self, specificity: Specificity3
     ) -> list[tuple[str, Specificity4, Any]]:
diff --git a/src/textual/css/stylesheet.py b/src/textual/css/stylesheet.py
index d441a2d12..81a4ff14b 100644
--- a/src/textual/css/stylesheet.py
+++ b/src/textual/css/stylesheet.py
@@ -114,7 +114,7 @@ class Stylesheet:
 
         _check_rule = self._check_rule
 
-        node.reset_styles()
+        node.styles.reset()
 
         # Get the default node CSS rules
         for key, default_specificity, value in node._default_rules:
diff --git a/tests/test_styles.py b/tests/test_styles.py
new file mode 100644
index 000000000..074ef06ad
--- /dev/null
+++ b/tests/test_styles.py
@@ -0,0 +1,11 @@
+from rich.style import Style
+
+from textual.css.styles import Styles
+
+
+def test_styles_reset():
+    styles = Styles()
+    styles.text_style = "not bold"
+    assert styles.text_style == Style(bold=False)
+    styles.reset()
+    assert styles.text_style is Style.null()