Replace error.html with optional more specific category error templates (4xx.html)

Author: davegaeddert

plain/plain/views/README.md

@@ -258,7 +258,10 @@ For example:
 - `templates/404.html` - Page not found
 - `templates/403.html` - Forbidden
 - `templates/500.html` - Server error
-- `templates/error.html` - Generic fallback for all errors
+- `templates/4xx.html` - Generic fallback for all 4xx errors
+- `templates/5xx.html` - Generic fallback for all 5xx errors
+
+Plain will first look for a specific status code template (e.g., `404.html`), then fall back to the category template (e.g., `4xx.html`). If neither exists, a plain HTTP response is returned.
 
 The templates receive a context with `status_code` and `exception` variables.
 

plain/plain/views/errors.py

@@ -29,7 +29,10 @@ def get_template_context(self) -> dict:
         return context
 
     def get_template_names(self) -> list[str]:
-        return [f"{self.status_code}.html", "error.html"]
+        # Try specific status code first (e.g. "404.html")
+        # Then fall back to category (e.g. "4xx.html" or "5xx.html")
+        category = f"{str(self.status_code)[0]}xx"
+        return [f"{self.status_code}.html", f"{category}.html"]
 
     def get_request_handler(self) -> Callable[[], Any]:
         return self.get  # All methods (post, patch, etc.) will use the get()