From 021339d4a7a6064b20c311616395a44df5fd791a Mon Sep 17 00:00:00 2001
From: David Guillot <dguillot@contexte.com>
Date: Thu, 28 Apr 2022 23:50:52 +0200
Subject: [PATCH 1/3] refactor(templatetags): make _RENDERED comment a constant

---
 django_components/templatetags/component_tags.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/django_components/templatetags/component_tags.py b/django_components/templatetags/component_tags.py
index 1db37157..19fce9c7 100644
--- a/django_components/templatetags/component_tags.py
+++ b/django_components/templatetags/component_tags.py
@@ -15,6 +15,9 @@ from django_components.middleware import (
 register = template.Library()
 
 
+RENDERED_COMMENT_TEMPLATE = "<!-- _RENDERED {name} -->"
+
+
 def get_components_from_registry(registry):
     """Returns a list unique components from the registry."""
 
@@ -197,7 +200,9 @@ class ComponentNode(Node):
             rendered_component = self.component.render(context)
             if self.should_render_dependencies:
                 return (
-                    f"<!-- _RENDERED {self.component._component_name} -->"
+                    RENDERED_COMMENT_TEMPLATE.format(
+                        name=self.component._component_name
+                    )
                     + rendered_component
                 )
             else:

From f67cd37dea6c175f4c144822ff9d5b53bbfc08b6 Mon Sep 17 00:00:00 2001
From: David Guillot <dguillot@contexte.com>
Date: Thu, 28 Apr 2022 19:45:11 +0200
Subject: [PATCH 2/3] feat(templatetags): fix #143, ability to preload
 components

---
 .../templatetags/component_tags.py            | 53 ++++++++++++++--
 tests/test_dependency_rendering.py            | 60 +++++++++++++++++++
 2 files changed, 107 insertions(+), 6 deletions(-)

diff --git a/django_components/templatetags/component_tags.py b/django_components/templatetags/component_tags.py
index 19fce9c7..d7c6620c 100644
--- a/django_components/templatetags/component_tags.py
+++ b/django_components/templatetags/component_tags.py
@@ -30,13 +30,36 @@ def get_components_from_registry(registry):
     return components
 
 
+def get_components_from_preload_str(preload_str):
+    """Returns a list of unique components from a comma-separated str"""
+
+    components = []
+    for component_name in preload_str.split(","):
+        component_name = component_name.strip()
+        if not component_name:
+            continue
+        component_class = registry.get(component_name)
+        components.append(component_class(component_name))
+
+    return components
+
+
 @register.simple_tag(name="component_dependencies")
-def component_dependencies_tag():
+def component_dependencies_tag(preload=""):
     """Marks location where CSS link and JS script tags should be rendered."""
 
     if is_dependency_middleware_active():
+        preloaded_dependencies = []
+        for component in get_components_from_preload_str(preload):
+            preloaded_dependencies.append(
+                RENDERED_COMMENT_TEMPLATE.format(
+                    name=component._component_name
+                )
+            )
         return mark_safe(
-            CSS_DEPENDENCY_PLACEHOLDER + JS_DEPENDENCY_PLACEHOLDER
+            "\n".join(preloaded_dependencies)
+            + CSS_DEPENDENCY_PLACEHOLDER
+            + JS_DEPENDENCY_PLACEHOLDER
         )
     else:
         rendered_dependencies = []
@@ -47,11 +70,20 @@ def component_dependencies_tag():
 
 
 @register.simple_tag(name="component_css_dependencies")
-def component_css_dependencies_tag():
+def component_css_dependencies_tag(preload=""):
     """Marks location where CSS link tags should be rendered."""
 
     if is_dependency_middleware_active():
-        return mark_safe(CSS_DEPENDENCY_PLACEHOLDER)
+        preloaded_dependencies = []
+        for component in get_components_from_preload_str(preload):
+            preloaded_dependencies.append(
+                RENDERED_COMMENT_TEMPLATE.format(
+                    name=component._component_name
+                )
+            )
+        return mark_safe(
+            "\n".join(preloaded_dependencies) + CSS_DEPENDENCY_PLACEHOLDER
+        )
     else:
         rendered_dependencies = []
         for component in get_components_from_registry(registry):
@@ -61,11 +93,20 @@ def component_css_dependencies_tag():
 
 
 @register.simple_tag(name="component_js_dependencies")
-def component_js_dependencies_tag():
+def component_js_dependencies_tag(preload=""):
     """Marks location where JS script tags should be rendered."""
 
     if is_dependency_middleware_active():
-        return mark_safe(JS_DEPENDENCY_PLACEHOLDER)
+        preloaded_dependencies = []
+        for component in get_components_from_preload_str(preload):
+            preloaded_dependencies.append(
+                RENDERED_COMMENT_TEMPLATE.format(
+                    name=component._component_name
+                )
+            )
+        return mark_safe(
+            "\n".join(preloaded_dependencies) + JS_DEPENDENCY_PLACEHOLDER
+        )
     else:
         rendered_dependencies = []
         for component in get_components_from_registry(registry):
diff --git a/tests/test_dependency_rendering.py b/tests/test_dependency_rendering.py
index 667636a2..cba1b29e 100644
--- a/tests/test_dependency_rendering.py
+++ b/tests/test_dependency_rendering.py
@@ -86,6 +86,42 @@ class ComponentMediaRenderingTests(SimpleTestCase):
             count=0,
         )
 
+    def test_preload_dependencies_render_when_no_components_used(self):
+        component.registry.register(name="test", component=SimpleComponent)
+
+        template = Template(
+            "{% load component_tags %}{% component_dependencies preload='test' %}"
+        )
+        rendered = create_and_process_template_response(template)
+        self.assertInHTML('<script src="script.js">', rendered, count=1)
+        self.assertInHTML(
+            '<link href="style.css" type="text/css" media="all" rel="stylesheet"/>',
+            rendered,
+            count=1,
+        )
+
+    def test_preload_js_dependencies_render_when_no_components_used(self):
+        component.registry.register(name="test", component=SimpleComponent)
+
+        template = Template(
+            "{% load component_tags %}{% component_js_dependencies preload='test' %}"
+        )
+        rendered = create_and_process_template_response(template)
+        self.assertInHTML('<script src="script.js">', rendered, count=1)
+
+    def test_preload_css_dependencies_render_when_no_components_used(self):
+        component.registry.register(name="test", component=SimpleComponent)
+
+        template = Template(
+            "{% load component_tags %}{% component_css_dependencies preload='test' %}"
+        )
+        rendered = create_and_process_template_response(template)
+        self.assertInHTML(
+            '<link href="style.css" type="text/css" media="all" rel="stylesheet"/>',
+            rendered,
+            count=1,
+        )
+
     def test_single_component_dependencies_render_when_used(self):
         component.registry.register(name="test", component=SimpleComponent)
 
@@ -101,6 +137,21 @@ class ComponentMediaRenderingTests(SimpleTestCase):
         )
         self.assertInHTML('<script src="script.js">', rendered, count=1)
 
+    def test_preload_dependencies_render_once_when_used(self):
+        component.registry.register(name="test", component=SimpleComponent)
+
+        template = Template(
+            "{% load component_tags %}{% component_dependencies preload='test' %}"
+            "{% component 'test' variable='foo' %}"
+        )
+        rendered = create_and_process_template_response(template)
+        self.assertInHTML(
+            '<link href="style.css" type="text/css" media="all" rel="stylesheet"/>',
+            rendered,
+            count=1,
+        )
+        self.assertInHTML('<script src="script.js">', rendered, count=1)
+
     def test_placeholder_removed_when_single_component_rendered(self):
         component.registry.register(name="test", component=SimpleComponent)
 
@@ -111,6 +162,15 @@ class ComponentMediaRenderingTests(SimpleTestCase):
         rendered = create_and_process_template_response(template)
         self.assertNotIn("_RENDERED", rendered)
 
+    def test_placeholder_removed_when_preload_rendered(self):
+        component.registry.register(name="test", component=SimpleComponent)
+
+        template = Template(
+            "{% load component_tags %}{% component_dependencies preload='test' %}"
+        )
+        rendered = create_and_process_template_response(template)
+        self.assertNotIn("_RENDERED", rendered)
+
     def test_single_component_css_dependencies(self):
         component.registry.register(name="test", component=SimpleComponent)
 

From 0ae04467c506219bfad13cee8fe91ca4f9f54dd3 Mon Sep 17 00:00:00 2001
From: David Guillot <dguillot@contexte.com>
Date: Thu, 28 Apr 2022 23:53:43 +0200
Subject: [PATCH 3/3] fix(tests): some minor anomalies

---
 tests/test_dependency_rendering.py | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/tests/test_dependency_rendering.py b/tests/test_dependency_rendering.py
index cba1b29e..d8315496 100644
--- a/tests/test_dependency_rendering.py
+++ b/tests/test_dependency_rendering.py
@@ -52,12 +52,7 @@ class ComponentMediaRenderingTests(SimpleTestCase):
             "{% load component_tags %}{% component_dependencies %}"
         )
         rendered = create_and_process_template_response(template)
-        self.assertInHTML('<script src="script.js>"', rendered, count=0)
-        self.assertInHTML(
-            '<link href="style.css" type="text/css" media="all" rel="stylesheet"/>',
-            rendered,
-            count=0,
-        )
+        self.assertInHTML('<script src="script.js">', rendered, count=0)
         self.assertInHTML(
             '<link href="style.css" type="text/css" media="all" rel="stylesheet"/>',
             rendered,
@@ -71,7 +66,7 @@ class ComponentMediaRenderingTests(SimpleTestCase):
             "{% load component_tags %}{% component_js_dependencies %}"
         )
         rendered = create_and_process_template_response(template)
-        self.assertInHTML('<script src="script.js>"', rendered, count=0)
+        self.assertInHTML('<script src="script.js">', rendered, count=0)
 
     def test_no_css_dependencies_when_no_components_used(self):
         component.registry.register(name="test", component=SimpleComponent)