Fix bad deprecation of Register.name_format (backport #9494)

qiskit/circuit/register.py

@@ -17,33 +17,35 @@
 """
 import re
 import itertools
+import warnings
 import numpy as np
 
 from qiskit.circuit.exceptions import CircuitError
 
-# Over-specific import to avoid cyclic imports.
-from qiskit.utils.deprecation import deprecate_function
+
+class _NameFormat:
+    REGEX = re.compile("[a-z][a-zA-Z0-9_]*")
+
+    def __get__(self, obj, objtype=None):
+        warnings.warn(
+            "Register.name_format is deprecated as of Qiskit Terra 0.23, and will be removed in a"
+            " future release. There is no longer a restriction on the names of registers, so the"
+            " attribute has no meaning any more.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.REGEX
 
 
 class Register:
     """Implement a generic register."""
 
     __slots__ = ["_name", "_size", "_bits", "_bit_indices", "_hash", "_repr"]
 
-    _name_format = re.compile("[a-z][a-zA-Z0-9_]*")
-
     # In historical version of Terra, registers' name had to conform to the OpenQASM 2 specification
     # (see appendix A of https://arxiv.org/pdf/1707.03429v2.pdf), and this regex enforced it.  That
     # restriction has been relaxed, so this is no longer necessary.
-    @property
-    @deprecate_function(
-        "Register.name_format is deprecated as of Qiskit Terra 0.23, and will be removed in a"
-        " future release. There is no longer a restriction on the names of registers, so the"
-        " attribute has no meaning any more."
-    )
-    def name_format(self):
-        # pylint: disable=missing-function-docstring
-        return self._name_format
+    name_format = _NameFormat()
 
     # Counter for the number of instances in this class.
     instances_counter = itertools.count()

releasenotes/notes/fix-register-name-format-deprecation-61ad5b06d618bb29.yaml

@@ -0,0 +1,10 @@
+---
+fixes:
+  - |
+    Fixed a bad deprecation of :attr:`.Register.name_format` which had made the class attribute
+    available only from instances and not the class.  When trying to send dynamic-circuits jobs to
+    hardware backends, this would frequently cause the error::
+
+      AttributeError: 'property' object has no attribute 'match'
+
+    Fixed `#9493 <https://github.com/Qiskit/qiskit-terra/issues/9493>`__.

test/python/circuit/test_register.py

@@ -120,3 +120,15 @@ def test_newstyle_register_eq(self, reg_type):
         bits_difftype = [difftype.bit_type() for _ in range(3)]
         reg_difftype = difftype(name="foo", bits=bits_difftype)
         self.assertNotEqual(reg_difftype, test_reg)
+
+    @data(QuantumRegister, ClassicalRegister, AncillaRegister)
+    def test_register_name_format_deprecation(self, reg_type):
+        """Test that the `Register.name_format` class data can be accessed and triggers its
+        deprecation correctly."""
+        # From instance:
+        reg_inst = reg_type(2)
+        with self.assertWarnsRegex(DeprecationWarning, "Register.name_format is deprecated"):
+            self.assertTrue(reg_inst.name_format.match("name"))
+        # From class:
+        with self.assertWarnsRegex(DeprecationWarning, "Register.name_format is deprecated"):
+            self.assertTrue(reg_type.name_format.match("name"))