Handle dataclass kw_only keyword correctly

[DanielNoord]

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Description

Type of Changes

	Type
✓	🐛 Bug fix

Related Issue

Closes pylint-dev/pylint#7290

Edit after merge: Closes pylint-dev/pylint#6550

[coveralls]

Pull Request Test Coverage Report for Build 2993872918

• 47 of 47 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.05%) to 92.4%

---

Totals
Change from base Build 2989127382:	0.05%
Covered Lines:	9750
Relevant Lines:	10552

---

💛 - Coveralls

[jacobtylerwalls]

Looking good, but I think the string contains test for the argument names needs to be more robust.

[jacobtylerwalls]

I see that it works, but for my understanding can you explain the iteration going on here?

[DanielNoord]

node.bases are nodes.Name. So, I get the first base node which then gets inferred, of which I get the first inference result. This should be the ClassDef.

This works because we mangle the __init__ of each dataclass so there is no need to iterate over all base classes, the last base is fine.

I use next(iter( as it is a nice safe guard against not finding any bases using the try ... except I needed anyway for the call to .infer().

[jacobtylerwalls]

I managed to break this assumption because "e" is contained in "ee":

This test will now fail:

diff --git a/tests/unittest_brain_dataclasses.py b/tests/unittest_brain_dataclasses.py
index a2077d1c..92a61a85 100644
--- a/tests/unittest_brain_dataclasses.py
+++ b/tests/unittest_brain_dataclasses.py
@@ -761,7 +761,7 @@ def test_kw_only_decorator() -> None:
     @dataclass(kw_only=True)
     class Foo:
         a: int
-        b: str
+        e: str
 
 
     @dataclass(kw_only=False)
@@ -776,7 +776,7 @@ def test_kw_only_decorator() -> None:
 
     @dataclass(kw_only=True)
     class Dee(Cee):
-        e: int
+        ee: int
 
 
     Foo.__init__  #@
@@ -789,31 +789,31 @@ def test_kw_only_decorator() -> None:
     foo_init: bases.UnboundMethod = next(foodef.infer())
     if PY310_PLUS:
         assert [a.name for a in foo_init.args.args] == ["self"]
-        assert [a.name for a in foo_init.args.kwonlyargs] == ["a", "b"]
+        assert [a.name for a in foo_init.args.kwonlyargs] == ["a", "e"]
     else:
-        assert [a.name for a in foo_init.args.args] == ["self", "a", "b"]
+        assert [a.name for a in foo_init.args.args] == ["self", "a", "e"]
         assert [a.name for a in foo_init.args.kwonlyargs] == []
 
     bar_init: bases.UnboundMethod = next(bardef.infer())
     if PY310_PLUS:
         assert [a.name for a in bar_init.args.args] == ["self", "c"]
-        assert [a.name for a in bar_init.args.kwonlyargs] == ["a", "b"]
+        assert [a.name for a in bar_init.args.kwonlyargs] == ["a", "e"]
     else:
-        assert [a.name for a in bar_init.args.args] == ["self", "a", "b", "c"]
+        assert [a.name for a in bar_init.args.args] == ["self", "a", "e", "c"]
         assert [a.name for a in bar_init.args.kwonlyargs] == []
 
     cee_init: bases.UnboundMethod = next(cee.infer())
     if PY310_PLUS:
         assert [a.name for a in cee_init.args.args] == ["self", "c", "d"]
-        assert [a.name for a in cee_init.args.kwonlyargs] == ["a", "b"]
+        assert [a.name for a in cee_init.args.kwonlyargs] == ["a", "e"]
     else:
-        assert [a.name for a in cee_init.args.args] == ["self", "a", "b", "c", "d"]
+        assert [a.name for a in cee_init.args.args] == ["self", "a", "e", "c", "d"]
         assert [a.name for a in cee_init.args.kwonlyargs] == []
 
     dee_init: bases.UnboundMethod = next(dee.infer())
     if PY310_PLUS:
         assert [a.name for a in dee_init.args.args] == ["self", "c", "d"]
-        assert [a.name for a in dee_init.args.kwonlyargs] == ["a", "b", "e"]
+        assert [a.name for a in dee_init.args.kwonlyargs] == ["a", "e", "e"]
     else:
-        assert [a.name for a in dee_init.args.args] == ["self", "a", "b", "c", "d", "e"]
+        assert [a.name for a in dee_init.args.args] == ["self", "a", "e", "c", "d", "ee"]
         assert [a.name for a in dee_init.args.kwonlyargs] == []

[DanielNoord]

😅

[DanielNoord]

This also closed pylint-dev/pylint#6550 and pylint-dev/pylint#5857