refactor: centralize numeric normalization

tests/preservation_helpers.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import ast
 import hashlib
 import re
 from pathlib import Path
@@ -33,6 +34,41 @@ def sha256(path: Path) -> str:
     return hashlib.sha256(path.read_bytes()).hexdigest()
 
 
+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),
+    )
+
+
+def module_contract(
+    path: Path,
+    *,
+    excluded_definitions: set[str] | None = None,
+    excluded_import_modules: set[str] | None = None,
+    exclude_imports: bool = False,
+) -> str:
+    excluded_definitions = excluded_definitions or set()
+    excluded_import_modules = excluded_import_modules or set()
+    tree = ast.parse(path.read_text(encoding="utf-8"), filename=str(path))
+    tree.body = [
+        node
+        for node in tree.body
+        if not (exclude_imports and isinstance(node, (ast.Import, ast.ImportFrom)))
+        and not (
+            isinstance(node, ast.ImportFrom)
+            and node.module in excluded_import_modules
+        )
+        and getattr(node, "name", None) not in excluded_definitions
+    ]
+    return ast.dump(tree, include_attributes=False)
+
+
 def reassembled_frontend_runtime() -> str:
     chunks: dict[tuple[int, int], str] = {}
     for path in FRONTEND_ROOT.rglob("*.js"):