Allow application creation from Blueprint at startup

sanic/app.py

@@ -547,6 +547,9 @@ class Sanic(BaseSanic, metaclass=TouchUpMeta):
                     "pre-registrations must use an application name."
                 )
 
+            if self.name in registry and _default in registry:
+                registry[_default].extend(registry.pop(self.name))
+
             registry = {
                 self.name if k is _default else k: v
                 for k, v in registry.items()
@@ -1712,7 +1715,8 @@ class Sanic(BaseSanic, metaclass=TouchUpMeta):
         version_prefix: str = "/v",
     ) -> Blueprint:
         if not name:
-            name = f"bp{len(Blueprint.__pre_registry__)}"
+            flat = [1 for x in Blueprint.__pre_registry__.values() for _ in x]
+            name = f"bp{len(flat)}"
         bp = Blueprint(
             name=name,
             url_prefix=url_prefix,

sanic/blueprints.py

@@ -472,6 +472,9 @@ class Blueprint(BaseSanic):
         strict_slashes: Optional[bool] = None,
         version_prefix: Union[str, Default] = _default,
     ) -> None:
+        if not hasattr(self.ctx, "_prereg"):
+            self.ctx._prereg = []
+        self.ctx._prereg.append(name)
         self.__class__.__pre_registry__[name].append(
             {
                 k: v

sanic/cli/app.py

@@ -10,7 +10,9 @@ from typing import Any, List, Union
 
 from sanic.app import Sanic
 from sanic.application.logo import get_logo
+from sanic.blueprints import Blueprint
 from sanic.cli.arguments import Group
+from sanic.helpers import _default
 from sanic.log import error_logger
 from sanic.simple import create_simple_server
 
@@ -20,6 +22,7 @@ class SanicArgumentParser(ArgumentParser):
 
 
 class SanicCLI:
+    DEFAULT_APP_NAME = "SANIC"
     DESCRIPTION = indent(
         f"""
 {get_logo(True)}
@@ -131,7 +134,17 @@ Or, a path to a directory to run as a simple HTTP server:
 
                 app_type_name = type(app).__name__
 
-                if not isinstance(app, Sanic):
+                if isinstance(app, Blueprint):
+                    bp = app
+                    name = (
+                        bp.ctx._prereg[0]
+                        if hasattr(bp.ctx, "_prereg")
+                        else _default
+                    )
+                    if name is _default:
+                        name = self.DEFAULT_APP_NAME
+                    app = Sanic(name)
+                elif not isinstance(app, Sanic):
                     raise ValueError(
                         f"Module is not a Sanic app, it is a {app_type_name}\n"
                         f"  Perhaps you meant {self.args.module}.app?"