Fix bug with nested composite analysis

qiskit_experiments/framework/composite/composite_analysis.py

@@ -96,13 +96,10 @@ def _run_analysis(self, experiment_data: ExperimentData):
             )
             analysis_results.append(result)
 
-        # Add callback to wait for all component analysis to finish before returning
+        # Wait for all component analysis to finish before returning
         # the parent experiment analysis results
-        def _wait_for_components(experiment_data, component_ids):
-            for comp_id in component_ids:
-                experiment_data.child_data(comp_id).block_for_results()
-
-        experiment_data.add_analysis_callback(_wait_for_components, component_ids=component_ids)
+        for comp_id in component_ids:
+            experiment_data.child_data(comp_id).block_for_results()
 
         return analysis_results, []
 

releasenotes/notes/fix-nested-comp-66a2b8b6e3b404be.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixes bug in :class:`.CompositeAnalysis` where analysis of nested
+    composite experiments could raise a RuntimeError.

test/test_composite.py

@@ -161,6 +161,20 @@ def test_composite_copy(self):
         self.check_attributes(new_instance)
         self.assertEqual(new_instance.parent_id, None)
 
+    def test_nested_composite(self):
+        """
+        Test nested parallel experiments.
+        """
+        exp1 = FakeExperiment([0, 2])
+        exp2 = FakeExperiment([1, 3])
+        exp3 = ParallelExperiment([exp1, exp2])
+        exp4 = BatchExperiment([exp3, exp1])
+        exp5 = ParallelExperiment([exp4, FakeExperiment([4])])
+        nested_exp = BatchExperiment([exp5, exp3])
+        expdata = nested_exp.run(FakeBackend()).block_for_results()
+        status = expdata.status()
+        self.assertEqual(status, "DONE")
+
     def test_analysis_replace_results_true(self):
         """
         Test replace results when analyzing composite experiment data