Fix pickling of conditioned custom gates from OpenQASM 2 import (Qisk…

…it#11175) (Qiskit#11258)

The condition of a gate defined by a `gate` statement in an OpenQASM 2
program was not previously exported as part of its state during
pickling, causing pickle roundtrips or deepcopies to lose the condition
on the new copy.

(cherry picked from commit 196221f)

Co-authored-by: Jake Lishman <[email protected]>

qiskit/qasm2/parse.py

@@ -324,14 +324,15 @@ def _define(self):
     # to pickle ourselves, we just eagerly create the definition and pickle that.
 
     def __getstate__(self):
-        return (self.name, self.num_qubits, self.params, self.definition)
+        return (self.name, self.num_qubits, self.params, self.definition, self.condition)
 
     def __setstate__(self, state):
-        name, num_qubits, params, definition = state
+        name, num_qubits, params, definition, condition = state
         super().__init__(name, num_qubits, params)
         self._gates = ()
         self._bytecode = ()
         self._definition = definition
+        self._condition = condition
 
 
 def _gate_builder(name, num_qubits, known_gates, bytecode):

releasenotes/notes/fix-qasm2-deepcopy-conditioned-gate-2fa75fee622c1fc0.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Conditioned custom gates imported from OpenQASM 2 will now correctly retain their conditions
+    when pickled and deep-copied.  Previously, any conditional custom gate (defined by a ``gate``
+    statement in an OpenQASM 2 file) would lose its condition when copied or pickled.

test/python/qasm2/test_structure.py

@@ -12,6 +12,7 @@
 
 # pylint: disable=missing-module-docstring,missing-class-docstring,missing-function-docstring
 
+import copy
 import io
 import math
 import os
@@ -696,6 +697,32 @@ def test_qpy_double_call_roundtrip(self):
             loaded = qpy.load(fptr)[0]
         self.assertEqual(loaded, qc)
 
+    def test_deepcopy_conditioned_defined_gate(self):
+        program = """
+            include "qelib1.inc";
+            gate my_gate a {
+                x a;
+            }
+            qreg q[1];
+            creg c[1];
+            if (c == 1) my_gate q[0];
+        """
+        parsed = qiskit.qasm2.loads(program)
+        my_gate = parsed.data[0].operation
+
+        self.assertEqual(my_gate.name, "my_gate")
+        self.assertEqual(my_gate.condition, (parsed.cregs[0], 1))
+
+        copied = copy.deepcopy(parsed)
+        copied_gate = copied.data[0].operation
+        self.assertEqual(copied_gate.name, "my_gate")
+        self.assertEqual(copied_gate.condition, (copied.cregs[0], 1))
+
+        pickled = pickle.loads(pickle.dumps(parsed))
+        pickled_gate = pickled.data[0].operation
+        self.assertEqual(pickled_gate.name, "my_gate")
+        self.assertEqual(pickled_gate.condition, (pickled.cregs[0], 1))
+
 
 class TestOpaque(QiskitTestCase):
     def test_simple(self):