Fixes issue #1427

changelog.d/1427.change.md

@@ -0,0 +1 @@
+Values passed to the `__init__()` method of `attrs` classes are now correctly passed to `__attrs_pre_init__()` instead of their default values (in cases where *kw_only* was not specified).

src/attr/_make.py

@@ -2126,8 +2126,9 @@ def _attrs_to_init_script(
     )
     lines.extend(extra_lines)
 
-    args = []
-    kw_only_args = []
+    args = []  # Parameters in the definition of __init__
+    pre_init_args = []  # Parameters in the call to __attrs_pre_init__
+    kw_only_args = []  # Used for both 'args' and 'pre_init_args' above
     attrs_to_validate = []
 
     # This is a dictionary of names to validator and converter callables.
@@ -2205,6 +2206,7 @@ def _attrs_to_init_script(
                 kw_only_args.append(arg)
             else:
                 args.append(arg)
+                pre_init_args.append(arg_name)
 
             if converter is not None:
                 lines.append(
@@ -2224,6 +2226,7 @@ def _attrs_to_init_script(
                 kw_only_args.append(arg)
             else:
                 args.append(arg)
+                pre_init_args.append(arg_name)
             lines.append(f"if {arg_name} is not NOTHING:")
 
             init_factory_name = _INIT_FACTORY_PAT % (a.name,)
@@ -2266,6 +2269,7 @@ def _attrs_to_init_script(
                 kw_only_args.append(arg_name)
             else:
                 args.append(arg_name)
+                pre_init_args.append(arg_name)
 
             if converter is not None:
                 lines.append(
@@ -2322,7 +2326,7 @@ def _attrs_to_init_script(
         lines.append(f"BaseException.__init__(self, {vals})")
 
     args = ", ".join(args)
-    pre_init_args = args
+    pre_init_args = ", ".join(pre_init_args)
     if kw_only_args:
         # leading comma & kw_only args
         args += f"{', ' if args else ''}*, {', '.join(kw_only_args)}"
@@ -2337,7 +2341,7 @@ def _attrs_to_init_script(
         pre_init_args += pre_init_kw_only_args
 
     if call_pre_init and pre_init_has_args:
-        # If pre init method has arguments, pass same arguments as `__init__`.
+        # If pre init method has arguments, pass the values given to __init__.
         lines[0] = f"self.__attrs_pre_init__({pre_init_args})"
 
     # Python <3.12 doesn't allow backslashes in f-strings.

tests/test_make.py

@@ -715,6 +715,49 @@ def __attrs_pre_init__(self, *, kw_and_default):
 
         assert 3 == val == inst.kw_and_default
 
+    @pytest.mark.usefixtures("with_and_without_validation")
+    def test_pre_init_with_mixture_of_defaults_and_kw_only(self):
+        """
+        Attrs should properly handle a mixture of positional, positional with
+        default, keyword-only, and keyword-only with default attributes when
+        passing values to __attrs_pre_init__.
+        """
+        g_val1 = None
+        g_val2 = None
+        g_val3 = None
+        g_val4 = None
+        g_val5 = None
+        g_val6 = None
+
+        @attr.define
+        class MixtureClass:
+            val1: int
+            val2: int = 100
+            val3: int = attr.field(factory=int)
+            val4: int = attr.field(kw_only=True)
+            val5: int = attr.field(default=100, kw_only=True)
+            val6: int = attr.field(factory=int, kw_only=True)
+
+            def __attrs_pre_init__(self, val1, val2, val3, val4, val5, val6):
+                nonlocal g_val1, g_val2, g_val3, g_val4, g_val5, g_val6
+                g_val1 = val1
+                g_val2 = val2
+                g_val3 = val3
+                g_val4 = val4
+                g_val5 = val5
+                g_val6 = val6
+
+        inst = MixtureClass(
+            val1=200, val2=200, val3=200, val4=200, val5=200, val6=200
+        )
+
+        assert 200 == g_val1 == inst.val1
+        assert 200 == g_val2 == inst.val2
+        assert 200 == g_val3 == inst.val3
+        assert 200 == g_val4 == inst.val4
+        assert 200 == g_val5 == inst.val5
+        assert 200 == g_val6 == inst.val6
+
     @pytest.mark.usefixtures("with_and_without_validation")
     def test_post_init(self):
         """