Fix lazy submodule loading and add changelog fragment

- Use sys.modules[mod_name].__dict__ instead of globals() so the
  lazy-loaded module is cached in the correct package when
  _make_getattr is used by attrs/__init__.py
- Add __dir__ to both attr and attrs packages so that converters
  and validators appear in dir() (tab-completion, introspection)
- Add changelog.d entry for this PR

Author: KRRT7

changelog.d/1547.change.md

@@ -0,0 +1 @@
+Deferred the import of `inspect` and the loading of the `validators` and `converters` submodules until first use, reducing `import attr`/`import attrs` time by ~25%.

src/attr/__init__.py

@@ -4,6 +4,8 @@
 Classes Without Boilerplate
 """
 
+import sys
+
 from functools import partial
 from typing import Callable, Literal, Protocol
 
@@ -92,7 +94,7 @@ def __getattr__(name: str) -> str:
             import importlib
 
             mod = importlib.import_module(f".{name}", mod_name)
-            globals()[name] = mod
+            sys.modules[mod_name].__dict__[name] = mod
             return mod
 
         if name not in ("__version__", "__version_info__"):
@@ -112,3 +114,7 @@ def __getattr__(name: str) -> str:
 
 
 __getattr__ = _make_getattr(__name__)
+
+
+def __dir__() -> list[str]:
+    return __all__

src/attrs/__init__.py

@@ -70,3 +70,7 @@
 ]
 
 __getattr__ = _make_getattr(__name__)
+
+
+def __dir__() -> list[str]:
+    return __all__