Improve performance of attr.astuple (#1469)

* Improve performance of attr.astuple

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Add news fragment

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Hynek Schlawack <hs@ox.cx>

Author: 3 people

changelog.d/1469.change.md

@@ -0,0 +1 @@
+The performance of `attrs.astuple()` has been improved by 49–270%.

src/attr/_funcs.py

@@ -278,8 +278,11 @@ def astuple(
         v = getattr(inst, a.name)
         if filter is not None and not filter(a, v):
             continue
+        value_type = type(v)
         if recurse is True:
-            if has(v.__class__):
+            if value_type in _ATOMIC_TYPES:
+                rv.append(v)
+            elif has(value_type):
                 rv.append(
                     astuple(
                         v,
@@ -289,7 +292,7 @@ def astuple(
                         retain_collection_types=retain,
                     )
                 )
-            elif isinstance(v, (tuple, list, set, frozenset)):
+            elif issubclass(value_type, (tuple, list, set, frozenset)):
                 cf = v.__class__ if retain is True else list
                 items = [
                     (
@@ -313,8 +316,8 @@ def astuple(
                     # Workaround for TypeError: cf.__new__() missing 1 required
                     # positional argument (which appears, for a namedturle)
                     rv.append(cf(*items))
-            elif isinstance(v, dict):
-                df = v.__class__ if retain is True else dict
+            elif issubclass(value_type, dict):
+                df = value_type if retain is True else dict
                 rv.append(
                     df(
                         (

tests/test_funcs.py

@@ -499,6 +499,23 @@ class A:
         with pytest.raises(TypeError, match=re.escape(message)):
             attr.astuple(instance, retain_collection_types=True)
 
+    def test_non_atomic_types(self, C):
+        """
+        Non-atomic types that don't have special treatment for are serialized
+        and the types are retained.
+        """
+
+        class Int(int):
+            pass
+
+        c = C(Int(10), [Int(1), 2])
+        expected = (Int(10), [Int(1), 2])
+
+        result = astuple(c)
+        assert expected == result
+        assert type(result[0]) is Int
+        assert type(result[1][0]) is Int
+
 
 class TestHas:
     """