Fix bugs and performance issues in rewrite-python (#6851)

* Fix bugs and performance issues in rewrite-python

- Fix shared class-level mutable dict in InMemoryExecutionContext that
  caused state leakage between instances
- Fix swapped last_access_time/last_modified_time args in
  FileAttributes.from_path
- Fix error message in Cursor.first_enclosing_or_throw using wrong
  variable (T.__name__ instead of type.__name__)
- Use identity check (is not) instead of equality (!=) in all 63
  PaddingHelper.padding properties to avoid O(n) __eq__ comparisons
- Use deque.popleft() instead of list.pop(0) in RpcReceiveQueue for
  O(1) message consumption
- Combine multiple replace() calls into single operations in
  visit_right_padded and parse_python_source
- Remove unused imports and dead code

* Extract shared utilities and buffer RPC stdin reads in rewrite-python

- Extract duplicated import helpers (get_qualid_name, get_name_string,
  get_alias_name, pad_right) into import_utils.py, replacing copies in
  add_import.py, remove_import.py, and change_import.py
- Extract duplicated format helpers (common_margin, concatenate_prefix)
  into format/_helpers.py, replacing copies in minimum_viable_spacing.py
  and normalize_format.py
- Replace byte-at-a-time os.read(fd, 1) in RPC server with a buffered
  _StdinBuffer that reads in 8 KB chunks, reducing syscalls per message
  from ~25+ to 1-2

Author: knutwannheden

rewrite-python/rewrite/src/rewrite/discovery.py

@@ -18,16 +18,13 @@
 
 import inspect
 from importlib.metadata import entry_points
-from typing import List, Tuple, Type, TYPE_CHECKING
+from typing import List, Tuple, Type
 
 from rewrite.category import CategoryDescriptor
 from rewrite.decorators import get_recipe_category
 from rewrite.marketplace import RecipeMarketplace
 from rewrite.recipe import Recipe
 
-if TYPE_CHECKING:
-    pass
-
 
 def discover_recipes() -> RecipeMarketplace:
     """

rewrite-python/rewrite/src/rewrite/execution.py

@@ -36,7 +36,8 @@ def put_message(self, key, value):
 
 
 class InMemoryExecutionContext(ExecutionContext):
-    _messages: dict[str, Any] = {}
+    def __init__(self):
+        self._messages: dict[str, Any] = {}
 
     def get_message(self, key: str, default_value=None) -> Any:
         return self._messages[key] if key in self._messages else default_value

rewrite-python/rewrite/src/rewrite/java/extensions.py

@@ -35,10 +35,11 @@ def visit_right_padded(v: 'JavaVisitor', right: Optional[JRightPadded[T]], p: P)
     if t is None:
         return None
 
-    right = right.replace(element=t)
-    right = right.replace(after=v.visit_space(right.after, p))
-    right = right.replace(markers=v.visit_markers(right.markers, p))
-    return right
+    after = v.visit_space(right.after, p)
+    markers = v.visit_markers(right.markers, p)
+    if t is right.element and after is right.after and markers is right.markers:
+        return right
+    return JRightPadded(t, after, markers)
 
 
 def visit_left_padded(v: 'JavaVisitor', left: Optional[JLeftPadded[T]], p: P) -> Optional[JLeftPadded[T]]:

rewrite-python/rewrite/src/rewrite/java/support_types.py

@@ -569,7 +569,7 @@ def padding(self) -> JContainer.PaddingHelper[J2]:
         else:
             p = self._padding()
             # noinspection PyProtectedMember
-            if p is None or p._t != self:
+            if p is None or p._t is not self:
                 p = JContainer.PaddingHelper(self)
                 object.__setattr__(self, '_padding', weakref.ref(p))
         return p