Implement Element.__html__.

This makes Element compatible with markupsafes escape() and Django's
django.utils.html.conditional_escape.

docs/changelog.md

@@ -1,6 +1,8 @@
 # Changelog
 
 ## next
+- Implement `Element.__html__`. This avoids double escaping when passed
+to `markupsafe.escape` and Django's `django.utils.html.conditional_escape`.
 - Raise errors directly on invalid children. This avoids cryptic stack traces.
 [PR #56](https://github.com/pelme/htpy/pull/56).
 - Raise TypeError rather than ValueError when invalid types are passed as

htpy/__init__.py

@@ -224,6 +224,8 @@ def __init__(self, name: str, attrs_str: str = "", children: Node = None) -> Non
     def __str__(self) -> _Markup:
         return _Markup("".join(self))
 
+    __html__ = __str__
+
     @t.overload
     def __call__(
         self: BaseElementSelf, id_class: str, attrs: dict[str, Attribute], **kwargs: Attribute

tests/test_django.py

@@ -7,7 +7,7 @@
 from django.forms.utils import ErrorList
 from django.template import Context, Template, TemplateDoesNotExist
 from django.template.loader import render_to_string
-from django.utils.html import escape
+from django.utils.html import conditional_escape, escape
 from django.utils.safestring import SafeString
 
 from htpy import Element, Node, div, li, ul
@@ -68,3 +68,8 @@ def test_system_checks_works(self) -> None:
         # Django 5.1 requires template backends to implement a check() method.
         # This test ensures that it does not crash.
         management.call_command("check")
+
+
+def test_conditional_escape() -> None:
+    result = conditional_escape(div["test"])  # type: ignore[arg-type]
+    assert result == "<div>test</div>"

tests/test_element.py

@@ -1,5 +1,5 @@
+import markupsafe
 import pytest
-from markupsafe import Markup
 from typing_extensions import assert_type
 
 import htpy
@@ -29,7 +29,7 @@ def test_void_element_repr() -> None:
 def test_markup_str() -> None:
     result = str(div(id="a"))
     assert isinstance(result, str)
-    assert isinstance(result, Markup)
+    assert isinstance(result, markupsafe.Markup)
     assert result == '<div id="a"></div>'
 
 
@@ -42,3 +42,16 @@ def test_element_type() -> None:
 
     assert_type(div()["a"], Element)
     assert isinstance(div()["a"], Element)
+
+
+def test_html_protocol() -> None:
+    element = div["test"]
+    result = element.__html__()
+    assert result == "<div>test</div>"
+    assert isinstance(result, markupsafe.Markup)
+
+
+def test_markupsafe_escape() -> None:
+    result = markupsafe.escape(div["test"])
+    assert result == "<div>test</div>"
+    assert isinstance(result, markupsafe.Markup)