Implement simple custom tag function

Author: MaddyGuthridge

pyhtml/__init__.py

@@ -294,12 +294,15 @@
 """
 # Disable Flake8, since it really doesn't like our docstring above
 # flake8: noqa
-from .__tag_base import Tag
+from .__tag_base import Tag, create_tag, SelfClosingTag, WhitespaceSensitiveTag
 
 from .__tags import input_, object_
 
 __all__ = [
     'Tag',
+    'create_tag',
+    'SelfClosingTag',
+    'WhitespaceSensitiveTag',
     'DangerousRawHtml',
     'Comment',
     'input_',

pyhtml/__tag_base.py

@@ -215,3 +215,37 @@ def _render(self, indent: int) -> list[str]:
 
         output += f"</{self._get_tag_name()}>"
         return output.splitlines()
+
+
+def create_tag(name: str, base: type[Tag] = Tag) -> type[Tag]:
+    """
+    Create a new PyHTML tag definition.
+
+    PyHTML already provides definitions for all standard HTML tags, so you
+    don't need to use this unless you are using a JavaScript library that
+    defines custom HTML elements.
+
+    Args:
+        name (str): the name of the tag. This is used during rendering, as
+                    `<{name}> ... </{name}>`.
+
+        base (type[Tag]): the base class to use for the custom tag. The new tag
+                          will inherit from this base class.
+
+    Returns:
+        type[Tag]: a new tag definition.
+    """
+
+    def _get_tag_name(self) -> str:
+        return name
+
+    # Generate custom type inheriting from given base class
+    CustomTag = type(
+        name,
+        (base,),
+        {
+            '_get_tag_name': _get_tag_name,
+        },
+    )
+
+    return CustomTag

tests/custom_tag_test.py

@@ -0,0 +1,18 @@
+"""
+# tests / custom tag test
+
+Test cases for generating custom tags.
+"""
+import pyhtml as p
+
+
+def test_generate_custom_tag():
+    t = p.create_tag('t')
+
+    assert str(t()) == '<t></t>'
+
+
+def test_base_class_set():
+    t = p.create_tag('t', p.WhitespaceSensitiveTag)
+
+    assert issubclass(t, p.WhitespaceSensitiveTag)