Add slots to components that can be filled when using component.

django_components/component.py

@@ -1,5 +1,9 @@
+from inspect import getfullargspec
+
 from django.forms.widgets import MediaDefiningClass
-from django.template.loader import render_to_string
+from django.template import Context
+from django.template.base import NodeList, TokenType, TextNode
+from django.template.loader import get_template
 from six import with_metaclass
 
 # Allow "component.AlreadyRegistered" instead of having to import these everywhere
@@ -16,9 +20,44 @@ class Component(with_metaclass(MediaDefiningClass)):
     def render_dependencies(self):
         return self.media.render()
 
-    def render(self, *args, **kwargs):
-        context = self.context(*args, **kwargs)
-        return render_to_string(self.template(context), context)
+    def slots_in_template(self, template):
+        nodelist = NodeList()
+        for node in template.template.nodelist:
+            if (
+                node.token.token_type == TokenType.BLOCK
+                and node.token.split_contents()[0] == "slot"
+            ):
+                nodelist.append(node)
+
+        return nodelist
+
+    def render(self, slots_filled=None, *args, **kwargs):
+        slots_filled = slots_filled or []
+        context_args_variables = getfullargspec(self.context).args[1:]
+        context_args = {key: kwargs[key] for key in context_args_variables if key in kwargs}
+        context = self.context(**context_args)
+        template = get_template(self.template(context))
+        slots_in_template = self.slots_in_template(template)
+
+        if slots_in_template:
+            valid_slot_names = set([slot.name for slot in slots_in_template])
+            nodelist = NodeList()
+            for node in template.template.nodelist:
+                if (
+                    node.token.token_type == TokenType.BLOCK
+                    and node.token.split_contents()[0] == "slot"
+                ):
+                    if node.name in valid_slot_names and node.name in slots_filled:
+                        nodelist.append(TextNode(slots_filled[node.name]))
+                    else:
+                        for node in node.nodelist:
+                            nodelist.append(node)
+                else:
+                    nodelist.append(node)
+
+            return nodelist.render(Context(context))
+
+        return template.render(context)
 
     class Media:
         css = {}