Interoperability with Django and Jinja using __html__() protocol

Author: collinanderson

fastcore/xml.py

@@ -76,7 +76,7 @@ def Html(*c, doctype=True, **kwargs)->FT:
     return (ft('!DOCTYPE', html=True, void_=True), res)
 
 # %% ../nbs/11_xml.ipynb
-def _escape(s): return '' if s is None else escape(s) if isinstance(s, str) else s
+def _escape(s): return '' if s is None else s.__html__() if hasattr(s, '__html__') else escape(s) if isinstance(s, str) else s
 
 # %% ../nbs/11_xml.ipynb
 def _to_attr(k,v):
@@ -115,6 +115,8 @@ def to_xml(elm, lvl=0):
     if not isvoid: res += f'{sp}{cltag}\n'
     return res
 
+FT.__html__ = to_xml
+
 # %% ../nbs/11_xml.ipynb
 def highlight(s, lang='xml'):
     "Markdown to syntax-highlight `s` in language `lang`"

nbs/11_xml.ipynb

@@ -264,7 +264,7 @@
    "outputs": [],
    "source": [
     "#| export\n",
-    "def _escape(s): return '' if s is None else escape(s) if isinstance(s, str) else s"
+    "def _escape(s): return '' if s is None else s.__html__() if hasattr(s, '__html__') else escape(s) if isinstance(s, str) else s"
    ]
   },
   {
@@ -317,7 +317,9 @@
     "    res = f'{sp}<{stag}>\\n'\n",
     "    res += ''.join(to_xml(c, lvl=lvl+2) for c in cs)\n",
     "    if not isvoid: res += f'{sp}{cltag}\\n'\n",
-    "    return res"
+    "    return res\n",
+    "\n",
+    "FT.__html__ = to_xml"
    ]
   },
   {
@@ -353,11 +355,52 @@
     "print(h)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "4713bd8d",
+   "metadata": {},
+   "source": [
+    "Interoperability both directions with Django and Jinja using the [__html__() protocol](https://jinja.palletsprojects.com/en/3.1.x/templates/#jinja-filters.escape)."
+   ]
+  },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 107,
    "id": "798ae1d2",
    "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "<div><b>Hello from Django</b></div>\n",
+      "\n",
+      "<div>\n",
+      "  <p>Hello from fastcore &lt;3</p>\n",
+      "</div>\n",
+      "\n"
+     ]
+    }
+   ],
+   "source": [
+    "class MockDjangoSafeString(str):\n",
+    "    def __html__(self):\n",
+    "        return self\n",
+    "\n",
+    "def mock_django_conditional_escape(s):\n",
+    "    return s.__html__() if hasattr(s, '__html__') else MockDjangoSafeString(escape(s))\n",
+    "\n",
+    "html_string_coming_from_django = MockDjangoSafeString('<b>Hello from Django</b>')\n",
+    "print(to_xml(Div(html_string_coming_from_django)))\n",
+    "\n",
+    "print(mock_django_conditional_escape(Div(P('Hello from fastcore <3'))))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 108,
+   "id": "5f0e91e0",
+   "metadata": {},
    "outputs": [],
    "source": [
     "#| export\n",