WIP Jinja support.

Author: ShaheedHaque

src/reactpy_django/templatetags/jinja.py

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+# Copyright © 2023 Innovatie Ltd. All rights reserved.
+"""
+Jinja support.
+"""
+import typing as t
+
+from django.template import RequestContext, loader
+from jinja2 import pass_context
+from jinja2.ext import Extension
+from jinja2.runtime import Context, Undefined
+
+from .reactpy import component as djt_component
+from .. import config
+
+
+class ReactPyExtension(Extension):
+    """
+    Jinja has more expressive power than core Django's templates, and can
+    directly handle expansions such as:
+
+        {{ component(*args, **kwargs) }}
+    """
+    DJT_TEMPLATE = 'reactpy/component.html'
+    #
+    # Therefore, there is no new tag to parse().
+    #
+    tags = {}
+
+    def __init__(self, environment):
+        super().__init__(environment)
+        #
+        # All we need is to add global "component" to the environment.
+        #
+        environment.globals["component"] = self._jinja_component
+
+    @pass_context
+    def _jinja_component(self, __context: Context, dotted_path: str, *args: t.Any, host: str | None = None,
+                         prerender: str = str(config.REACTPY_PRERENDER), **kwargs: t.Any) -> t.Union[t.Any, Undefined]:
+        """
+        This method is used to embed an existing ReactPy component into your
+        Jinja2 template.
+
+        Args:
+            dotted_path: String of the fully qualified name of a component.
+            *args: The positional arguments to provide to the component.
+
+        Keyword Args:
+            class: The HTML class to apply to the top-level component div.
+            key: Force the component's root node to use a specific key value. \
+                Using key within a template tag is effectively useless.
+            host: The host to use for the ReactPy connections. If set to `None`, \
+                the host will be automatically configured. \
+                Example values include: `localhost:8000`, `example.com`, `example.com/subdir`
+            prerender: Configures whether to pre-render this component, which \
+                enables SEO compatibility and reduces perceived latency.
+            **kwargs: The keyword arguments to provide to the component.
+
+        Returns:
+            Whatever the components returns.
+        """
+        djt_context = RequestContext(__context.parent['request'], autoescape=__context.eval_ctx.autoescape)
+        context = djt_component(djt_context, dotted_path, *args, host=host, prerender=prerender, **kwargs)
+        #
+        # TODO: can this be usefully cached?
+        #
+        result = loader.render_to_string(self.DJT_TEMPLATE, context, __context.parent['request'])
+        return result