From 9cc87b2c2b8a1f66baea1ef624a2b9370eccbe13 Mon Sep 17 00:00:00 2001
From: ShipItChief <shipitchief@last-word.fr>
Date: Sun, 19 Apr 2026 10:07:06 +0000
Subject: [PATCH] fix(parser): handle bytes input in escape_char using
 to_unicode

escape_char was annotated to accept str | bytes but used str.replace()
operations directly, causing TypeError when bytes input contained characters
that needed escaping (comma, semicolon, backslash, newline).

Use to_unicode() to convert bytes to str before applying replacements,
matching the approach used in unescape_char. This also corrects the
return type from str | bytes to str.

Adds test_escape_char_bytes verifying all escape patterns work with
bytes input.

Closes #1226
---
 CHANGES.rst                         |  1 +
 src/icalendar/parser/string.py      |  6 +++---
 src/icalendar/tests/test_parsing.py | 13 ++++++++++++-
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/CHANGES.rst b/CHANGES.rst
index 745f16d9b..20c210195 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -42,6 +42,7 @@ New features
 Bug fixes
 ~~~~~~~~~
 
+- Fixed :func:`~icalendar.parser.string.escape_char` to accept :class:`bytes` input by converting it to :class:`str` with :func:`~icalendar.parser_tools.to_unicode` before applying replacements. :issue:`1226`
 - ...
 
 Documentation
diff --git a/src/icalendar/parser/string.py b/src/icalendar/parser/string.py
index 209503831..9242c09c7 100644
--- a/src/icalendar/parser/string.py
+++ b/src/icalendar/parser/string.py
@@ -2,10 +2,10 @@
 
 import re
 
-from icalendar.parser_tools import DEFAULT_ENCODING
+from icalendar.parser_tools import DEFAULT_ENCODING, to_unicode
 
 
-def escape_char(text: str | bytes) -> str | bytes:
+def escape_char(text: str | bytes) -> str:
     r"""Format value according to iCalendar TEXT escaping rules.
 
     Escapes special characters in text values according to :rfc:`5545#section-3.3.11`
@@ -29,7 +29,7 @@ def escape_char(text: str | bytes) -> str | bytes:
         6. ``"\n"`` -> ``r"\n"`` (transform a newline character to a literal, or raw,
            newline character)
     """
-    assert isinstance(text, (str, bytes))
+    text = to_unicode(text)
     # NOTE: ORDER MATTERS!
     return (
         text.replace(r"\N", "\n")
diff --git a/src/icalendar/tests/test_parsing.py b/src/icalendar/tests/test_parsing.py
index 3a73badc3..e2283fe10 100644
--- a/src/icalendar/tests/test_parsing.py
+++ b/src/icalendar/tests/test_parsing.py
@@ -9,7 +9,7 @@
 from icalendar.cal.calendar import Calendar
 from icalendar.cal.component_factory import ComponentFactory
 from icalendar.cal.event import Event
-from icalendar.parser import Contentline, Parameters, unescape_char
+from icalendar.parser import Contentline, Parameters, unescape_char, escape_char
 
 
 @pytest.mark.parametrize(
@@ -280,3 +280,14 @@ def test_create_a_component():
     my_component_class = factory.get_component_class("My-Component")
     assert my_component_class.name == "MY-COMPONENT"
     assert my_component_class.__name__ == "MyComponent"
+
+
+def test_escape_char_bytes():
+    """Test that escape_char accepts bytes input and returns str."""
+    assert escape_char(b"hello,world") == "hello\\,world"
+    assert escape_char(b"hello;world") == "hello\\;world"
+    assert escape_char(b"hello\\world") == "hello\\\\world"
+    assert escape_char(b"hello\nworld") == "hello\\nworld"
+    assert escape_char(b"hello\r\nworld") == "hello\\nworld"
+    assert escape_char(b"hello\\Nworld") == "hello\\nworld"
+    assert escape_char("hello,world") == "hello\\,world"