python: render extended error pages using common routine

cloudflare_error_page/__init__.py

@@ -1,36 +1,50 @@
 import html
-import os
 import secrets
 from datetime import datetime, timezone
+from typing import Any, Optional
 
 from jinja2 import Environment, PackageLoader, Template, select_autoescape
 
 env = Environment(
-    loader=PackageLoader("cloudflare_error_page"),
+    loader=PackageLoader(__name__),
     autoescape=select_autoescape(),
     trim_blocks=True,
     lstrip_blocks=True,
 )
 
-default_template = env.get_template("error.html")
+default_template: Template = env.get_template("error.html")
 
 
-def fill_params(params: dict):
+def render(params: dict,
+           allow_html: bool = True,
+           template: Optional[Template] = None,
+           *args: Any,
+           **kwargs: Any) -> str:
+    '''Render a customized Cloudflare error page.
+
+    :param params: Parameters passed to the template. Refer to the project homepage for more information.
+    :param allow_html: Allow output raw HTML content from parameters. Set to False if you don't trust the source of the params.
+    :param template: Jinja template used to render the error page. Default template will be used if ``template`` is None.
+        Override this to extend or customize the base template.
+    :param args: Additional positional arguments passed to ``Template.render`` function.
+    :param kwargs: Additional keyword arguments passed to ``Template.render`` function.
+    :return: The rendered error page as a string.
+    '''
+    if not template:
+        template = default_template
+
+    params = {**params}
+
     if not params.get('time'):
         utc_now = datetime.now(timezone.utc)
         params['time'] = utc_now.strftime("%Y-%m-%d %H:%M:%S UTC")
     if not params.get('ray_id'):
         params['ray_id'] = secrets.token_hex(8)
-
-
-def render(params: dict, allow_html: bool=True) -> str:
-    """
-    Render a customized Cloudflare error page.
-    """
-    params = {**params}
-    fill_params(params)
     if not allow_html:
         params['what_happened'] = html.escape(params.get('what_happened', ''))
         params['what_can_i_do'] = html.escape(params.get('what_can_i_do', ''))
 
-    return default_template.render(params=params)
+    return template.render(params=params, *args, **kwargs)
+
+
+__all__ = ['default_template', 'render']

editor/server/share.py

@@ -14,8 +14,8 @@ from flask import (
 from jinja2 import Environment, select_autoescape
 
 from cloudflare_error_page import (
-    fill_params as fill_template_params,
-    default_template as cf_template
+    default_template as cf_template,
+    render as render_cf_error_page,
 )
 
 from . import (
@@ -127,14 +127,12 @@ def get(name: str):
             'text': 'CF Error Page Editor',
             'link': request.host_url[:-1] + url_for('editor.index') + f'#from={name}',
         }
-        # Always escape HTML
-        params['what_happened'] = html.escape(params.get('what_happened', '')) # TODO: common render function?
-        params['what_can_i_do'] = html.escape(params.get('what_can_i_do', ''))
         fill_cf_template_params(params)
-        fill_template_params(params)
         sanitize_page_param_links(params)
 
-        return template.render(base=cf_template,
-                               params=params,
-                               url=request.url,
-                               description='Cloudflare error page')
+        return render_cf_error_page(params=params,
+                                    allow_html=False,
+                                    template=template,
+                                    base=cf_template,
+                                    url=request.url,
+                                    description='Cloudflare error page')