Rename plugin.loader to plugin.template

- Add helper function for rendering a template

InvenTree/InvenTree/settings.py

@@ -343,7 +343,7 @@ TEMPLATES = [
             ],
             'loaders': [(
                 'django.template.loaders.cached.Loader', [
-                    'plugin.loader.PluginTemplateLoader',
+                    'plugin.template.PluginTemplateLoader',
                     'django.template.loaders.filesystem.Loader',
                     'django.template.loaders.app_directories.Loader',
                 ])

InvenTree/plugin/loader.py

@@ -1,19 +0,0 @@
-"""
-load templates for loaded plugins
-"""
-from django.template.loaders.filesystem import Loader as FilesystemLoader
-from pathlib import Path
-
-from plugin import registry
-
-
-class PluginTemplateLoader(FilesystemLoader):
-
-    def get_dirs(self):
-        dirname = 'templates'
-        template_dirs = []
-        for plugin in registry.plugins.values():
-            new_path = Path(plugin.path) / dirname
-            if Path(new_path).is_dir():
-                template_dirs.append(new_path)  # pragma: no cover
-        return tuple(template_dirs)

InvenTree/plugin/template.py

@@ -0,0 +1,66 @@
+"""
+load templates for loaded plugins
+"""
+
+import logging
+from pathlib import Path
+
+from django import template
+from django.template.loaders.filesystem import Loader as FilesystemLoader
+
+from plugin import registry
+
+
+logger = logging.getLogger('inventree')
+
+
+class PluginTemplateLoader(FilesystemLoader):
+    """
+    A custom template loader which allows loading of templates from installed plugins.
+
+    Each plugin can register templates simply by providing a 'templates' directory in its root path.
+
+    The convention is that each 'templates' directory contains a subdirectory with the same name as the plugin,
+    e.g. templates/myplugin/my_template.html
+
+    In this case, the template can then be loaded (from any plugin!) by loading "myplugin/my_template.html".
+
+    The separate plugin-named directories help keep the templates separated and uniquely identifiable.
+    """
+
+    def get_dirs(self):
+        dirname = 'templates'
+        template_dirs = []
+
+        for plugin in registry.plugins.values():
+            new_path = Path(plugin.path) / dirname
+            if Path(new_path).is_dir():
+                template_dirs.append(new_path)  # pragma: no cover
+
+        return tuple(template_dirs)
+
+
+def render_template(plugin, template_file, context=None):
+    """
+    Locate and render a template file, available in the global template context.
+    """
+
+    print("render_template", "->", template_file)
+    print("Context:")
+    print(context)
+
+    try:
+        tmp = template.loader.get_template(template_file)
+    except template.TemplateDoesNotExist:
+        logger.error(f"Plugin {plugin.slug} could not locate template '{template_file}'")
+
+        return f"""
+        <div class='alert alert-block alert-danger'>
+        Template file <em>{template_file}</em> does not exist.
+        </div>
+        """
+
+    # Render with the provided context
+    html = tmp.render(context)
+
+    return html