fix bug in BirdLoader asset scanning if None nodelist (#68)

* fix `TypeError` if nodelist is `None` when scanning for components in `BirdLoader`

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* remove commented out code

* make mypy happy

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: joshuadavidthomas

CHANGELOG.md

@@ -18,6 +18,10 @@ and this project attempts to adhere to [Semantic Versioning](https://semver.org/
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed a `TypeError` in the `BirdLoader` when scanning for assets if a `Template` or `Node` had a `None` nodelist. This could occur with self-closing `{% bird component / %}` components and their corresponding `BirdNode` instances.
+
 ## [0.6.0]
 
 ### Added

src/django_bird/_typing.py

@@ -1,6 +1,10 @@
 from __future__ import annotations
 
 import sys
+from typing import TypeGuard
+
+from django.template.base import Node
+from django.template.base import Template
 
 if sys.version_info >= (3, 12):
     from typing import override as typing_override
@@ -12,3 +16,7 @@
 override = typing_override
 
 TagBits = list[str]
+
+
+def _has_nodelist(node: Template | Node) -> TypeGuard[Template]:
+    return hasattr(node, "nodelist")

src/django_bird/loader.py

@@ -13,6 +13,7 @@
 from django.template.loader_tags import IncludeNode
 from django.template.loaders.filesystem import Loader as FileSystemLoader
 
+from ._typing import _has_nodelist
 from ._typing import override
 from .compiler import Compiler
 from .components import components
@@ -48,23 +49,27 @@ def get_contents(self, origin: Origin) -> str:
             cache.set(cache_key, compiled, timeout=None)
         return compiled
 
-    def _scan_for_components(self, template: Template | Node, context: Context) -> None:
-        if not hasattr(template, "nodelist"):
+    def _scan_for_components(self, node: Template | Node, context: Context) -> None:
+        if isinstance(node, BirdNode):
+            component = components.get_component(node.name)
+            self.asset_registry.register(component)
+
+        if not _has_nodelist(node) or node.nodelist is None:
             return
 
-        for node in template.nodelist:
-            if isinstance(node, BirdNode):
-                component = components.get_component(node.name)
+        for child in node.nodelist:
+            if isinstance(child, BirdNode):
+                component = components.get_component(child.name)
                 self.asset_registry.register(component)
 
-            if isinstance(node, ExtendsNode):
-                parent_template = node.get_parent(context)
+            if isinstance(child, ExtendsNode):
+                parent_template = child.get_parent(context)
                 self._scan_for_components(parent_template, context)
 
-            if isinstance(node, IncludeNode):
-                template_name = node.template.token.strip("'\"")
+            if isinstance(child, IncludeNode):
+                template_name = child.template.token.strip("'\"")
                 included_template = self.engine.get_template(template_name)
                 self._scan_for_components(included_template, context)
 
-            if hasattr(node, "nodelist"):
-                self._scan_for_components(node, context)
+            if hasattr(child, "nodelist"):
+                self._scan_for_components(child, context)

tests/test_loader.py

@@ -1,9 +1,17 @@
 from __future__ import annotations
 
 import pytest
+from django.template.base import Node
+from django.template.base import NodeList
+from django.template.base import Template
+from django.template.context import Context
+from django.template.engine import Engine
 from django.template.loader import get_template
 
 from django_bird.loader import BIRD_TAG_PATTERN
+from django_bird.loader import BirdLoader
+from django_bird.params import Params
+from django_bird.templatetags.tags.bird import BirdNode
 
 
 @pytest.mark.parametrize(
@@ -99,3 +107,37 @@ def test_asset_registry(
     components = loader.asset_registry.components
 
     assert len(components) == 3
+
+
+@pytest.mark.parametrize(
+    "node,expected_count",
+    [
+        (Template("{% bird button %}Click me{% endbird %}"), 1),
+        (BirdNode(name="button", params=Params([]), nodelist=None), 1),
+        (
+            BirdNode(
+                name="button",
+                params=Params([]),
+                nodelist=NodeList(
+                    [BirdNode(name="button", params=Params([]), nodelist=None)],
+                ),
+            ),
+            1,
+        ),
+        (type("NodeWithNoneNodelist", (Node,), {"nodelist": None})(), 0),
+        (Template("{% bird button %}{% bird button %}{% endbird %}{% endbird %}"), 1),
+    ],
+)
+def test_scan_for_components(
+    node, expected_count, create_bird_template, create_bird_asset
+):
+    button = create_bird_template("button", "<button>Click me</button>")
+    create_bird_asset(button, ".button { color: blue; }", "css")
+    create_bird_asset(button, "console.log('button');", "js")
+
+    loader = BirdLoader(Engine.get_default())
+    context = Context()
+
+    loader._scan_for_components(node, context)
+
+    assert len(loader.asset_registry.components) == expected_count