Change barrier/delay default behavior

oqpy/program.py

@@ -384,19 +384,31 @@ def declare(
         return self
 
     def delay(
-        self, time: AstConvertible, qubits_or_frames: AstConvertible | Iterable[AstConvertible] = ()
+        self,
+        time: AstConvertible,
+        qubits_or_frames: AstConvertible | Iterable[AstConvertible] | None = None,
     ) -> Program:
         """Apply a delay to a set of qubits or frames."""
-        if not isinstance(qubits_or_frames, Iterable):
-            qubits_or_frames = [qubits_or_frames]
+        if isinstance(qubits_or_frames, Iterable) and not any(True for _ in qubits_or_frames):
+            return self
+        elif qubits_or_frames is None:
+            ast_qubits_or_frames = []
+        else:
+            if not isinstance(qubits_or_frames, Iterable):
+                qubits_or_frames = [qubits_or_frames]
+            ast_qubits_or_frames = map_to_ast(self, qubits_or_frames)
         ast_duration = to_ast(self, convert_float_to_duration(time))
-        ast_qubits_or_frames = map_to_ast(self, qubits_or_frames)
         self._add_statement(ast.DelayInstruction(ast_duration, ast_qubits_or_frames))
         return self
 
-    def barrier(self, qubits_or_frames: Iterable[AstConvertible]) -> Program:
+    def barrier(self, qubits_or_frames: Iterable[AstConvertible] | None = None) -> Program:
         """Apply a barrier to a set of qubits or frames."""
-        ast_qubits_or_frames = map_to_ast(self, qubits_or_frames)
+        if isinstance(qubits_or_frames, Iterable) and not any(True for _ in qubits_or_frames):
+            return self
+        elif qubits_or_frames is None:
+            ast_qubits_or_frames = []
+        else:
+            ast_qubits_or_frames = map_to_ast(self, qubits_or_frames)
         self._add_statement(ast.QuantumBarrier(ast_qubits_or_frames))
         return self
 

tests/test_directives.py

@@ -862,6 +862,36 @@ def multiply(int[32] x, int[32] y) -> int[32] {
     _check_respects_type_hints(prog)
 
 
+def test_barrier_delay_arguments():
+    port = PortVar("portname")
+    frame = FrameVar(port, 1e9, name="frame0")
+    frame1 = FrameVar(port, 1.5e9, name="frame1")
+    prog = Program()
+    prog.barrier()
+    prog.delay(1e-7)
+    prog.barrier([])
+    prog.delay(2e-7, [])
+    prog.barrier([frame, frame1])
+    prog.delay(3e-7, frame1)
+    prog.delay(4e-7, [frame, frame1])
+
+    expected = textwrap.dedent(
+        """
+        OPENQASM 3.0;
+        port portname;
+        frame frame0 = newframe(portname, 1000000000.0, 0);
+        frame frame1 = newframe(portname, 1500000000.0, 0);
+        barrier;
+        delay[100.0ns];
+        barrier frame0, frame1;
+        delay[300.0ns] frame1;
+        delay[400.0ns] frame0, frame1;
+        """
+    ).strip()
+
+    assert prog.to_qasm() == expected
+
+
 def test_box_and_timings():
     constant = declare_waveform_generator("constant", [("length", duration), ("iq", complex128)])
 
@@ -1501,8 +1531,8 @@ def _to_oqpy_expression(self):
         """
         OPENQASM 3.0;
         duration a1 = 100.0ns;
-        duration a2 = 100.0ns;
         frame f1;
+        duration a2 = 100.0ns;
         a1 = 2;
         delay[a2] f1;
         """