Rework of context handling (#18)

Co-authored-by: rbeard0330 <@dul2k3BKW6m>

django_components/component.py

@@ -1,5 +1,4 @@
 from django.forms.widgets import MediaDefiningClass
-from django.template import Context
 from django.template.base import NodeList, TextNode
 from django.template.loader import get_template
 from django.utils.safestring import mark_safe
@@ -8,12 +7,6 @@ from six import with_metaclass
 # Allow "component.AlreadyRegistered" instead of having to import these everywhere
 from django_components.component_registry import AlreadyRegistered, ComponentRegistry, NotRegistered  # noqa
 
-# Python 2 compatibility
-try:
-    from inspect import getfullargspec
-except ImportError:
-    from inspect import getargspec as getfullargspec
-
 # Django < 2.1 compatibility
 try:
     from django.template.base import TokenType
@@ -49,52 +42,40 @@ class Component(with_metaclass(MediaDefiningClass)):
         return mark_safe("\n".join(self.media.render_js()))
 
     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(node for node in template.template.nodelist if is_slot_node(node))
 
-        return nodelist
-
-    def render(self, slots_filled=None, *args, **kwargs):
+    def render(self, context, slots_filled=None):
         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])
+        # If there are no slots, then we can simply render the template
+        if not slots_in_template:
+            return template.template.render(context)
+
+        # Otherwise, we need to assemble and render a nodelist containing the nodes from the template, slots that were
+        # provided when the component was called (previously rendered by the component's render method) and the
+        # unrendered default slots
         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:
+            if is_slot_node(node):
+                if node.name in slots_filled:
                     nodelist.append(TextNode(slots_filled[node.name]))
                 else:
-                        for node in node.nodelist:
-                            nodelist.append(node)
+                    nodelist.extend(node.nodelist)
             else:
                 nodelist.append(node)
 
-            render_context = Context(context)
-            with render_context.bind_template(template.template):
-                return nodelist.render(render_context)
-
-        return template.render(context)
+        return nodelist.render(context)
 
     class Media:
         css = {}
         js = []
 
 
+def is_slot_node(node):
+    return node.token.token_type == TokenType.BLOCK and node.token.split_contents()[0] == "slot"
+
+
 # This variable represents the global component registry
 registry = ComponentRegistry()

django_components/templatetags/component_tags.py

@@ -88,7 +88,8 @@ def component_js_dependencies_tag():
 def component_tag(name, *args, **kwargs):
     component_class = registry.get(name)
     component = component_class()
-    return component.render(*args, **kwargs)
+    context = template.Context(component.context(*args, **kwargs))
+    return component.render(context)
 
 
 class SlotNode(Node):
@@ -129,27 +130,30 @@ def do_slot(parser, token, component=None):
 
 
 class ComponentNode(Node):
-    def __init__(self, component, extra_context, slots):
-        extra_context = extra_context or {}
-        self.component, self.extra_context, self.slots = component, extra_context, slots
+    def __init__(self, component, context_kwargs, slots):
+        self.context_kwargs = context_kwargs or {}
+        self.component, self.slots = component, slots
 
     def __repr__(self):
         return "<Component Node: %s. Contents: %r>" % (self.component, self.slots)
 
     def render(self, context):
-        extra_context = {
+        # Resolve FilterExpressions and Variables that were passed as args to the component, then call component's
+        # context method to get values to insert into the context
+        resolved_context_kwargs = {
             key: context_item.resolve(context) if hasattr(context_item, 'resolve') else context_item
-            for key, context_item in self.extra_context.items()
+            for key, context_item in self.context_kwargs.items()
         }
-        context.update(extra_context)
+        extra_context = self.component.context(**resolved_context_kwargs)
 
+        with context.update(extra_context):
             self.slots.render(context)
-
             if COMPONENT_CONTEXT_KEY in context.render_context:
                 slots_filled = context.render_context[COMPONENT_CONTEXT_KEY][self.component]
-            return self.component.render(slots_filled=slots_filled, **context.flatten())
+            else:
+                slots_filled = []
 
-        return self.component.render(**extra_context)
+            return self.component.render(context, slots_filled=slots_filled)
 
 
 @register.tag("component_block")
@@ -187,9 +191,9 @@ def do_component(parser, token):
     component_class = registry.get(component_name)
     component = component_class()
 
-    extra_context = {}
+    context_kwargs = {}
     if len(bits) > 2:
-        extra_context = component.context(**token_kwargs(bits[2:], parser))
+        context_kwargs = token_kwargs(bits[2:], parser)
 
     slots_filled = NodeList()
     tag_name = bits[0]
@@ -205,4 +209,4 @@ def do_component(parser, token):
         elif tag_name == "endcomponent_block":
             break
 
-    return ComponentNode(component, extra_context, slots_filled)
+    return ComponentNode(component, context_kwargs, slots_filled)

tests/templates/incrementer.html

@@ -0,0 +1,2 @@
+{% load component_tags %}<p class="incrementer">value={{ value }};calls={{ calls }}</p>
+{% slot 'content' %}{% endslot %}

tests/templates/parent_template.html

@@ -0,0 +1,12 @@
+{% load component_tags %}
+
+<div>
+    <h1>Parent content</h1>
+    {% component name="variable_display" shadowing_variable='override' new_variable='unique_val' %}
+</div>
+<div>
+    {% slot 'content' %}
+        <h2>Slot content</h2>
+        {% component name="variable_display" shadowing_variable='slot_default_override' new_variable='slot_default_unique' %}
+    {% endslot %}
+</div>

tests/templates/parent_with_args_template.html

@@ -0,0 +1,12 @@
+{% load component_tags %}
+
+<div>
+    <h1>Parent content</h1>
+    {% component name="variable_display" shadowing_variable=inner_parent_value new_variable='unique_val' %}
+</div>
+<div>
+    {% slot 'content' %}
+        <h2>Slot content</h2>
+        {% component name="variable_display" shadowing_variable='slot_default_override' new_variable=inner_parent_value %}
+    {% endslot %}
+</div>

tests/templates/variable_display.html

@@ -0,0 +1,4 @@
+{% load component_tags %}
+
+<h1>Shadowing variable = {{ shadowing_variable }}</h1>
+<h1>Uniquely named variable = {{ unique_variable }}</h1>

tests/test_component.py

@@ -1,5 +1,7 @@
 from textwrap import dedent
 
+from django.template import Context
+
 from django_components import component
 
 from .django_test_setup import *  # NOQA
@@ -29,13 +31,14 @@ class ComponentRegistryTest(SimpleTestCase):
                 js = ["script.js"]
 
         comp = SimpleComponent()
+        context = Context(comp.context(variable="test"))
 
         self.assertHTMLEqual(comp.render_dependencies(), dedent("""
             <link href="style.css" type="text/css" media="all" rel="stylesheet">
             <script src="script.js"></script>
         """).strip())
 
-        self.assertHTMLEqual(comp.render(variable="test"), dedent("""
+        self.assertHTMLEqual(comp.render(context), dedent("""
             Variable: <strong>test</strong>
         """).lstrip())
 
@@ -66,8 +69,9 @@ class ComponentRegistryTest(SimpleTestCase):
                 return "filtered_template.html"
 
         comp = FilteredComponent()
+        context = Context(comp.context(var1="test1", var2="test2"))
 
-        self.assertHTMLEqual(comp.render(var1="test1", var2="test2"), dedent("""
+        self.assertHTMLEqual(comp.render(context), dedent("""
             Var1: <strong>test1</strong>
             Var2 (uppercased): <strong>TEST2</strong>
         """).lstrip())

tests/test_context.py

@@ -0,0 +1,227 @@
+from django.template import Context, Template
+
+from django_components import component
+
+from .django_test_setup import *  # NOQA
+from .testutils import Django111CompatibleSimpleTestCase as SimpleTestCase
+
+
+class ParentComponent(component.Component):
+    def context(self):
+        return {
+            "shadowing_variable": 'NOT SHADOWED'
+        }
+
+    def template(self, context):
+        return "parent_template.html"
+
+
+class ParentComponentWithArgs(component.Component):
+    def context(self, parent_value):
+        return {
+            "inner_parent_value": parent_value
+        }
+
+    def template(self, context):
+        return "parent_with_args_template.html"
+
+
+class VariableDisplay(component.Component):
+    def context(self, shadowing_variable, new_variable):
+        return {
+            "shadowing_variable": shadowing_variable,
+            "unique_variable": new_variable
+        }
+
+    def template(self, context):
+        return "variable_display.html"
+
+
+class IncrementerComponent(component.Component):
+    def context(self, value=0):
+        value = int(value)
+        if hasattr(self, 'call_count'):
+            self.call_count += 1
+        else:
+            self.call_count = 1
+        return {
+            "value": value + 1,
+            "calls": self.call_count
+        }
+
+    def template(self, context):
+        return "incrementer.html"
+
+
+component.registry.register(name='parent_component', component=ParentComponent)
+component.registry.register(name='parent_with_args', component=ParentComponentWithArgs)
+component.registry.register(name='variable_display', component=VariableDisplay)
+component.registry.register(name='incrementer', component=IncrementerComponent)
+
+
+class ContextTests(SimpleTestCase):
+    def test_nested_component_context_shadows_parent_with_unfilled_slots_and_component_tag(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component 'parent_component' %}")
+        rendered = template.render(Context())
+
+        self.assertIn('<h1>Shadowing variable = override</h1>', rendered, rendered)
+        self.assertIn('<h1>Shadowing variable = slot_default_override</h1>', rendered, rendered)
+        self.assertNotIn('<h1>Shadowing variable = NOT SHADOWED</h1>', rendered, rendered)
+
+    def test_nested_component_instances_have_unique_context_with_unfilled_slots_and_component_tag(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component name='parent_component' %}")
+        rendered = template.render(Context())
+
+        self.assertIn('<h1>Uniquely named variable = unique_val</h1>', rendered, rendered)
+        self.assertIn('<h1>Uniquely named variable = slot_default_unique</h1>', rendered, rendered)
+
+    def test_nested_component_context_shadows_parent_with_unfilled_slots_and_component_block_tag(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component_block 'parent_component' %}{% endcomponent_block %}")
+        rendered = template.render(Context())
+
+        self.assertIn('<h1>Shadowing variable = override</h1>', rendered, rendered)
+        self.assertIn('<h1>Shadowing variable = slot_default_override</h1>', rendered, rendered)
+        self.assertNotIn('<h1>Shadowing variable = NOT SHADOWED</h1>', rendered, rendered)
+
+    def test_nested_component_instances_have_unique_context_with_unfilled_slots_and_component_block_tag(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component_block 'parent_component' %}{% endcomponent_block %}")
+        rendered = template.render(Context())
+
+        self.assertIn('<h1>Uniquely named variable = unique_val</h1>', rendered, rendered)
+        self.assertIn('<h1>Uniquely named variable = slot_default_unique</h1>', rendered, rendered)
+
+    def test_nested_component_context_shadows_parent_with_filled_slots(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component_block 'parent_component' %}"
+                            "{% slot 'content' %}{% component name='variable_display' "
+                            "shadowing_variable='shadow_from_slot' new_variable='unique_from_slot' %}{% endslot %}"
+                            "{% endcomponent_block %}")
+        rendered = template.render(Context())
+
+        self.assertIn('<h1>Shadowing variable = override</h1>', rendered, rendered)
+        self.assertIn('<h1>Shadowing variable = shadow_from_slot</h1>', rendered, rendered)
+        self.assertNotIn('<h1>Shadowing variable = NOT SHADOWED</h1>', rendered, rendered)
+
+    def test_nested_component_instances_have_unique_context_with_filled_slots(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component_block 'parent_component' %}"
+                            "{% slot 'content' %}{% component name='variable_display' "
+                            "shadowing_variable='shadow_from_slot' new_variable='unique_from_slot' %}{% endslot %}"
+                            "{% endcomponent_block %}")
+        rendered = template.render(Context())
+
+        self.assertIn('<h1>Uniquely named variable = unique_val</h1>', rendered, rendered)
+        self.assertIn('<h1>Uniquely named variable = unique_from_slot</h1>', rendered, rendered)
+
+    def test_nested_component_context_shadows_outer_context_with_unfilled_slots_and_component_tag(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component name='parent_component' %}")
+        rendered = template.render(Context({'shadowing_variable': 'NOT SHADOWED'}))
+
+        self.assertIn('<h1>Shadowing variable = override</h1>', rendered, rendered)
+        self.assertIn('<h1>Shadowing variable = slot_default_override</h1>', rendered, rendered)
+        self.assertNotIn('<h1>Shadowing variable = NOT SHADOWED</h1>', rendered, rendered)
+
+    def test_nested_component_context_shadows_outer_context_with_unfilled_slots_and_component_block_tag(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component_block 'parent_component' %}{% endcomponent_block %}")
+        rendered = template.render(Context({'shadowing_variable': 'NOT SHADOWED'}))
+
+        self.assertIn('<h1>Shadowing variable = override</h1>', rendered, rendered)
+        self.assertIn('<h1>Shadowing variable = slot_default_override</h1>', rendered, rendered)
+        self.assertNotIn('<h1>Shadowing variable = NOT SHADOWED</h1>', rendered, rendered)
+
+    def test_nested_component_context_shadows_outer_context_with_filled_slots(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component_block 'parent_component' %}"
+                            "{% slot 'content' %}{% component name='variable_display' "
+                            "shadowing_variable='shadow_from_slot' new_variable='unique_from_slot' %}{% endslot %}"
+                            "{% endcomponent_block %}")
+        rendered = template.render(Context({'shadowing_variable': 'NOT SHADOWED'}))
+
+        self.assertIn('<h1>Shadowing variable = override</h1>', rendered, rendered)
+        self.assertIn('<h1>Shadowing variable = shadow_from_slot</h1>', rendered, rendered)
+        self.assertNotIn('<h1>Shadowing variable = NOT SHADOWED</h1>', rendered, rendered)
+
+
+class ParentArgsTests(SimpleTestCase):
+    def test_parent_args_can_be_drawn_from_context(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component_block 'parent_with_args' parent_value=parent_value %}"
+                            "{% endcomponent_block %}")
+        rendered = template.render(Context({'parent_value': 'passed_in'}))
+
+        self.assertIn('<h1>Shadowing variable = passed_in</h1>', rendered, rendered)
+        self.assertIn('<h1>Uniquely named variable = passed_in</h1>', rendered, rendered)
+        self.assertNotIn('<h1>Shadowing variable = NOT SHADOWED</h1>', rendered, rendered)
+
+    def test_parent_args_available_outside_slots(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component_block 'parent_with_args' parent_value='passed_in' %}{%endcomponent_block %}")
+        rendered = template.render(Context())
+
+        self.assertIn('<h1>Shadowing variable = passed_in</h1>', rendered, rendered)
+        self.assertIn('<h1>Uniquely named variable = passed_in</h1>', rendered, rendered)
+        self.assertNotIn('<h1>Shadowing variable = NOT SHADOWED</h1>', rendered, rendered)
+
+    def test_parent_args_available_in_slots(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component_block 'parent_with_args' parent_value='passed_in' %}"
+                            "{% slot 'content' %}{% component name='variable_display' "
+                            "shadowing_variable='value_from_slot' new_variable=inner_parent_value %}{% endslot %}"
+                            "{%endcomponent_block %}")
+        rendered = template.render(Context())
+
+        self.assertIn('<h1>Shadowing variable = value_from_slot</h1>', rendered, rendered)
+        self.assertIn('<h1>Uniquely named variable = passed_in</h1>', rendered, rendered)
+        self.assertNotIn('<h1>Shadowing variable = NOT SHADOWED</h1>', rendered, rendered)
+
+
+class ContextCalledOnceTests(SimpleTestCase):
+    def test_one_context_call_with_simple_component(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component name='incrementer' %}")
+        rendered = template.render(Context()).strip()
+
+        self.assertEqual(rendered, '<p class="incrementer">value=1;calls=1</p>', rendered)
+
+    def test_one_context_call_with_simple_component_and_arg(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component name='incrementer' value='2' %}")
+        rendered = template.render(Context()).strip()
+
+        self.assertEqual(rendered, '<p class="incrementer">value=3;calls=1</p>', rendered)
+
+    def test_one_context_call_with_component_block(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component_block 'incrementer' %}{% endcomponent_block %}")
+        rendered = template.render(Context()).strip()
+
+        self.assertEqual(rendered, '<p class="incrementer">value=1;calls=1</p>', rendered)
+
+    def test_one_context_call_with_component_block_and_arg(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component_block 'incrementer' value='3' %}{% endcomponent_block %}")
+        rendered = template.render(Context()).strip()
+
+        self.assertEqual(rendered, '<p class="incrementer">value=4;calls=1</p>', rendered)
+
+    def test_one_context_call_with_slot(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component_block 'incrementer' %}{% slot 'content' %}"
+                            "<p>slot</p>{% endslot %}{% endcomponent_block %}")
+        rendered = template.render(Context()).strip()
+
+        self.assertEqual(rendered, '<p class="incrementer">value=1;calls=1</p>\n<p>slot</p>', rendered)
+
+    def test_one_context_call_with_slot_and_arg(self):
+        template = Template("{% load component_tags %}{% component_dependencies %}"
+                            "{% component_block 'incrementer' value='3' %}{% slot 'content' %}"
+                            "<p>slot</p>{% endslot %}{% endcomponent_block %}")
+        rendered = template.render(Context()).strip()
+
+        self.assertEqual(rendered, '<p class="incrementer">value=4;calls=1</p>\n<p>slot</p>', rendered)