POC for compatibility mode

sanic/__version__.py

@@ -1 +1,10 @@
-__version__ = "22.12.0"
+__version__ = "23.3.0"
+__compatibility__ = "22.12"
+
+from inspect import currentframe, stack
+
+for frame_info in stack():
+    if frame_info.frame is not currentframe():
+        for member, value in frame_info.frame.f_globals.items():
+            if member.startswith("__") and member.isupper():
+                __compatibility__ = value

sanic/breaking/__init__.py

@@ -0,0 +1,18 @@
+from sanic.__version__ import __compatibility__
+
+if __compatibility__ == "22.12":
+    from .v22_12.request import (
+        File,
+        Request,
+        RequestParameters,
+        parse_multipart_form,
+    )
+elif __compatibility__ == "23.3":
+    from .v23_3.request import (
+        File,
+        Request,
+        RequestParameters,
+        parse_multipart_form,
+    )
+else:
+    raise RuntimeError(f"Unknown compatibility value: {__compatibility__}")

sanic/breaking/v23_3/request.py

@@ -0,0 +1,9 @@
+from ..v22_12.request import File
+from ..v22_12.request import Request as LegacyRequest
+from ..v22_12.request import RequestParameters, parse_multipart_form
+
+
+class Request(LegacyRequest):
+    @property
+    def something_new(self):
+        return 123

setup.cfg

@@ -1,2 +1,4 @@
 [flake8]
 ignore = E203, W503
+per-file-ignores =
+    sanic/app.py:E402