PY-81861 Pattern matching for dataclasses - allow matching a subset of attributes

(cherry picked from commit 30a865e64cee7be630567b7d23223fc79eac9dbf)

IJ-MR-168826

GitOrigin-RevId: 8383913015485a6b6e477131c47d502bb655dd30

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;

python/testSrc/com/jetbrains/python/PyPatternTypeTest.java

@@ -673,6 +673,26 @@ match x:
                    """);
   }
   
+  // 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() {
     doTestByText("""