refactor: establish standalone application boundary

tests/test_http_dispatch.py

@@ -1,6 +1,8 @@
 from __future__ import annotations
 
+import ast
 import unittest
+from pathlib import Path
 
 from backend.application import (
     AUTHENTICATED_POST_HANDLERS,
@@ -9,6 +11,23 @@ from backend.application import (
 )
 
 
+APP_ROOT = Path(__file__).resolve().parents[1]
+
+
+def class_methods(path: Path, class_name: str) -> set[str]:
+    tree = ast.parse(path.read_text(encoding="utf-8"), filename=str(path))
+    owner = next(
+        node
+        for node in tree.body
+        if isinstance(node, ast.ClassDef) and node.name == class_name
+    )
+    return {
+        node.name
+        for node in owner.body
+        if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef))
+    }
+
+
 class HttpDispatchContractTests(unittest.TestCase):
     @staticmethod
     def handler(path: str, calls: list[str]) -> RequestHandler:
@@ -78,6 +97,49 @@ class HttpDispatchContractTests(unittest.TestCase):
 
         self.assertEqual(calls, ["auth", "csrf", f"access:POST:{path}"])
 
+    def test_application_composition_and_route_ownership_stay_narrow(self) -> None:
+        application = APP_ROOT / "backend" / "application.py"
+        dispatch = APP_ROOT / "backend" / "http" / "dispatch.py"
+        self.assertLessEqual(len(application.read_text(encoding="utf-8").splitlines()), 220)
+        self.assertLessEqual(len(dispatch.read_text(encoding="utf-8").splitlines()), 150)
+        self.assertEqual(class_methods(application, "DashboardService"), {"__init__"})
+        self.assertEqual(class_methods(application, "RequestHandler"), set())
+        self.assertEqual(
+            class_methods(dispatch, "ApplicationHttpDispatchMixin"),
+            {"_dispatch_named_handler", "do_GET", "do_POST", "do_DELETE"},
+        )
+
+        expected_route_owners = {
+            "accounts", "alerts", "auction", "dragon_tiger", "heaven", "market",
+            "mentor", "pools", "popularity", "review", "rotation", "screener",
+            "sentiment", "system", "themes",
+        }
+        route_files = {
+            path.parent.name: path
+            for path in (APP_ROOT / "backend" / "features").glob("*/routes.py")
+        }
+        self.assertEqual(set(route_files), expected_route_owners)
+        for path in route_files.values():
+            source = path.read_text(encoding="utf-8")
+            self.assertLessEqual(len(source.splitlines()), 120, path.name)
+            self.assertNotIn("backend.application", source)
+            self.assertNotRegex(source, r"\bSERVICE\b")
+
+    def test_application_service_methods_have_single_domain_owners(self) -> None:
+        owners = (
+            ("features/system/service.py", "SystemServiceMixin", 300),
+            ("features/accounts/application.py", "AccountApplicationMixin", 100),
+            ("jobs/service.py", "JobServiceMixin", 80),
+        )
+        claimed: set[str] = set()
+        for relative, class_name, line_limit in owners:
+            path = APP_ROOT / "backend" / relative
+            methods = class_methods(path, class_name)
+            self.assertTrue(claimed.isdisjoint(methods))
+            claimed.update(methods)
+            self.assertLessEqual(len(path.read_text(encoding="utf-8").splitlines()), line_limit)
+        self.assertEqual(len(claimed), 27)
+
 
 if __name__ == "__main__":
     unittest.main()