From 7efaf9a137440f3b2bc273507e9cbedb70701ddb Mon Sep 17 00:00:00 2001
From: "Aleksandr.Govenko" <aleksandr.govenko@jetbrains.com>
Date: Tue, 1 Jul 2025 18:51:26 +0200
Subject: [PATCH] PY-81861 Pattern matching for dataclasses - allow matching a
 subset of attributes

GitOrigin-RevId: 30a865e64cee7be630567b7d23223fc79eac9dbf
---
 .../python/psi/impl/PyClassPatternImpl.java   |  2 +-
 .../jetbrains/python/PyPatternTypeTest.java   | 20 +++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/python/python-psi-impl/src/com/jetbrains/python/psi/impl/PyClassPatternImpl.java b/python/python-psi-impl/src/com/jetbrains/python/psi/impl/PyClassPatternImpl.java
index 1c3498194261..85e7d8239092 100644
--- a/python/python-psi-impl/src/com/jetbrains/python/psi/impl/PyClassPatternImpl.java
+++ b/python/python-psi-impl/src/com/jetbrains/python/psi/impl/PyClassPatternImpl.java
@@ -115,7 +115,7 @@ public class PyClassPatternImpl extends PyElementImpl implements PyClassPattern
         }
 
         List<String> matchArgs = getMatchArgs(classType, context);
-        if (matchArgs == null || matchArgs.size() > arguments.size()) return null;
+        if (matchArgs == null || index >= matchArgs.size()) return null;
 
         final PyTypedElement instanceAttribute = as(resolveTypeMember(classType, matchArgs.get(index), context), PyTypedElement.class);
         if (instanceAttribute == null) return null;
diff --git a/python/testSrc/com/jetbrains/python/PyPatternTypeTest.java b/python/testSrc/com/jetbrains/python/PyPatternTypeTest.java
index 3cd469944a00..8ce67ed21d9c 100644
--- a/python/testSrc/com/jetbrains/python/PyPatternTypeTest.java
+++ b/python/testSrc/com/jetbrains/python/PyPatternTypeTest.java
@@ -672,6 +672,26 @@ match x:
         assert_type(z, str)
                    """);
   }
+  
+  // PY-81861
+  public void testDataclassPartialCapture() {
+    doTestByText("""
+from dataclasses import dataclass
+from typing import assert_type
+
+
+@dataclass
+class A:
+    a: int
+    b: str
+
+
+x = A(1, "a")
+match x:
+    case A(y):
+        assert_type(y, int)
+                   """);
+  }
 
   // PY-79832
   public void testMatchClassPatternSelfCaptureParameterized() {