refactor: centralize numeric normalization

tests/test_preservation_slice_market.py

@@ -11,12 +11,14 @@ import realtime_aggregator
 import tushare_client
 from backend.bootstrap import config as bootstrap_config
 from backend.data import realtime
+from backend.data.numbers import finite_number
 from backend.data.providers import ifind_client as canonical_ifind
 from backend.data.providers import tushare_client as canonical_tushare
 from backend.features.market import charts
 from tests.preservation_helpers import (
     assert_frontend_runtime_matches_audited_baseline,
     assert_moved_asset_matches,
+    function_contract,
 )
 
 
@@ -102,18 +104,6 @@ def top_level_definitions(path: Path) -> dict[str, str]:
     }
 
 
-def function_contract(path: Path, name: str) -> tuple[str, str]:
-    tree = ast.parse(path.read_text(encoding="utf-8"), filename=str(path))
-    function = next(
-        node for node in tree.body if isinstance(node, ast.FunctionDef) and node.name == name
-    )
-    body = ast.Module(body=function.body, type_ignores=[])
-    return (
-        ast.dump(function.args, include_attributes=False),
-        ast.dump(body, include_attributes=False),
-    )
-
-
 class MarketSliceSourceEquivalenceTests(unittest.TestCase):
     def test_market_service_methods_are_exact_original_ast(self) -> None:
         original = class_methods(ORIGINAL_ROOT / "server.py", "DashboardService")
@@ -154,10 +144,17 @@ class MarketSliceSourceEquivalenceTests(unittest.TestCase):
         )
         for original, migrated in exact_moves:
             self.assertEqual(sha256(ORIGINAL_ROOT / original), sha256(APP_ROOT / migrated))
+        original_tushare = top_level_definitions(ORIGINAL_ROOT / "tushare_client.py")
+        original_tushare.pop("_number")
         self.assertEqual(
-            top_level_definitions(ORIGINAL_ROOT / "tushare_client.py"),
+            original_tushare,
             top_level_definitions(APP_ROOT / "backend/data/providers/tushare_client.py"),
         )
+        self.assertEqual(
+            function_contract(ORIGINAL_ROOT / "tushare_client.py", "_number"),
+            function_contract(APP_ROOT / "backend/data/numbers.py", "finite_number"),
+        )
+        self.assertIs(canonical_tushare._number, finite_number)
         original_charts = top_level_definitions(ORIGINAL_ROOT / "chart_data_provider.py")
         original_charts.pop("_stock_market_code")
         self.assertEqual(