Fix is_sampled and its test (#1126)

* is_sampled and test fix * changelog * fix
PennyLaneAI · Mar 9, 2021 · 12c3dc2 · 12c3dc2
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diff --git a/.github/CHANGELOG.md b/.github/CHANGELOG.md
@@ -237,6 +237,10 @@
 
 <h3>Bug fixes</h3>
 
+* Fixes a bug and a test where the ``QuantumTape.is_sampled`` attribute was not
+  being updated.
+  [(#1126)](https://github.com/PennyLaneAI/pennylane/pull/1126)
+
 * Fixes a bug where `BasisEmbedding` would not accept inputs whose bits are all ones 
   or all zeros. 
   [(#1114)](https://github.com/PennyLaneAI/pennylane/pull/1114)
@@ -261,7 +265,7 @@
 This release contains contributions from (in alphabetical order):
 
 Thomas Bromley, Olivia Di Matteo, Kyle Godbey, Diego Guala, Josh Izaac, Daniel Polatajko, Chase Roberts,
-Sankalp Sanand, Pritish Sehzpaul, Maria Schuld.
+Sankalp Sanand, Pritish Sehzpaul, Maria Schuld, Antal Száva.
 
 # Release 0.14.1 (current release)
 

diff --git a/pennylane/tape/tapes/tape.py b/pennylane/tape/tapes/tape.py
@@ -379,6 +379,8 @@ def _update_circuit_info(self):
             [op.wires for op in self.operations + self.observables]
         )
         self.num_wires = len(self.wires)
+
+        self.is_sampled = any(m.return_type is Sample for m in self.measurements)
         self.all_sampled = all(m.return_type is Sample for m in self.measurements)
 
     def _update_observables(self):

diff --git a/tests/tape/tapes/test_tape.py b/tests/tape/tapes/test_tape.py
@@ -856,9 +856,14 @@ def circuit():
                 qml.T(wires=0)
                 return sample(qml.PauliZ(0))
 
-            qnode = qml.tape.QNode(circuit, dev)
+            # Choosing parameter-shift not to swap the device under the hood
+            qnode = qml.tape.QNode(circuit, dev, diff_method="parameter-shift")
             qnode()
 
+            # Double-checking that the T gate is not supported
+            assert "T" not in qnode.device.operations
+            assert "T" not in qnode._original_device.operations
+
             assert qnode.qtape.is_sampled
 
 class TestExecution: