Fix workflow filters that map to no workloads

lib/ramble/ramble/test/cmd/workspace.py

@@ -2240,3 +2240,29 @@ def test_workspace_info_software(request):
     assert "spack-pkg" in output
     assert "pip-test" in output
     assert "spack-test" not in output
+
+
+def test_workspace_no_empty_workloads(request):
+    workspace_name = request.node.name
+    global_args = ["-w", workspace_name]
+
+    with ramble.workspace.create(workspace_name) as ws:
+        ws.write()
+
+        workspace(
+            "manage",
+            "experiments",
+            "basic",
+            "--wf",
+            "nothing*",
+            "-v",
+            "n_nodes=1",
+            "-v",
+            "n_ranks=1",
+            global_args=global_args,
+        )
+
+        with open(ws.config_file_path) as f:
+            data = f.read()
+            assert "basic:" not in data
+            assert "workloads: {}" not in data

lib/ramble/ramble/workspace/workspace.py

@@ -1141,6 +1141,8 @@ def yaml_add_comment_before_key(
 
         import ruamel.yaml as yaml
 
+        edited = False
+
         workspace_vars = self.get_workspace_vars()
         apps_dict = self.get_applications().copy()
 
@@ -1219,6 +1221,7 @@ def yaml_add_comment_before_key(
             workload_names = [ramble.expander.Expander.expansion_str(workload_name_variable)]
 
         for workload_name in workload_names:
+            edited = True
             if workload_name not in workloads_dict:
                 workloads_dict[workload_name] = syaml.syaml_dict()
                 workloads_dict[workload_name][namespace.experiment] = syaml.syaml_dict()
@@ -1301,11 +1304,11 @@ def yaml_add_comment_before_key(
                 if namespace.matrix not in exp_dict:
                     exp_dict[namespace.matrix] = exp_matrix.copy()
 
-        if not self.dry_run:
+        if edited and not self.dry_run:
             ramble.config.config.update_config(
                 namespace.application, apps_dict, scope=self.ws_file_config_scope_name()
             )
-        else:
+        elif edited:
             workspace_dict = self._get_workspace_dict()
             workspace_dict[namespace.ramble][namespace.application] = apps_dict