Avoid `@lru_cache` on methods

The problem with `@lru_cache` on methods is that it also captures `self`
and leaks it until the entry is evicted (if ever).

src/_pytest/assertion/rewrite.py

@@ -554,6 +554,7 @@ def set_location(node, lineno, col_offset):
     return node
 
 
+@functools.lru_cache(maxsize=1)
 def _get_assertion_exprs(src: bytes) -> Dict[int, str]:
     """Return a mapping from {lineno: "assertion test expression"}."""
     ret: Dict[int, str] = {}
@@ -675,10 +676,6 @@ class AssertionRewriter(ast.NodeVisitor):
             self.enable_assertion_pass_hook = False
         self.source = source
 
-    @functools.lru_cache(maxsize=1)
-    def _assert_expr_to_lineno(self) -> Dict[int, str]:
-        return _get_assertion_exprs(self.source)
-
     def run(self, mod: ast.Module) -> None:
         """Find all assert statements in *mod* and rewrite them."""
         if not mod.body:
@@ -906,7 +903,7 @@ class AssertionRewriter(ast.NodeVisitor):
 
             # Passed
             fmt_pass = self.helper("_format_explanation", msg)
-            orig = self._assert_expr_to_lineno()[assert_.lineno]
+            orig = _get_assertion_exprs(self.source)[assert_.lineno]
             hook_call_pass = ast.Expr(
                 self.helper(
                     "_call_assertion_pass",

src/_pytest/config/__init__.py

@@ -522,7 +522,6 @@ class PytestPluginManager(PluginManager):
                 if x.is_dir():
                     self._getconftestmodules(x, importmode, rootpath)
 
-    @lru_cache(maxsize=128)
     def _getconftestmodules(
         self, path: Path, importmode: Union[str, ImportMode], rootpath: Path
     ) -> List[types.ModuleType]: