fix(storcli2): treat absent "System Overview" as no controllers

pkg/implementation/controllergetter/storcli2.go

@@ -114,23 +114,48 @@ func (s *StorCLI2) Controllers() ([]*raidcontroller.RAIDController, error) {
 	controllers := make([]*raidcontroller.RAIDController, 0)
 
 	for i := range cmd.Controllers {
-		overview, err := utils.UnmarshalToSlice[storcli2SystemOverview](
-			cmd.Controllers[i].ResponseData, "System Overview",
-		)
+		found, err := s.controllersFromOverview(cmd.Controllers[i])
 		if err != nil {
-			return nil, errors.Wrap(err, "failed to unmarshal system overview")
+			return nil, err
 		}
 
-		for j := range overview {
-			metadata := &raidcontroller.Metadata{ID: overview[j].Ctrl}
+		controllers = append(controllers, found...)
+	}
 
-			controller, err := s.Controller(metadata)
-			if err != nil {
-				return nil, errors.Wrapf(err, "failed to get controller %d", metadata.ID)
-			}
+	return controllers, nil
+}
 
-			controllers = append(controllers, controller)
+// controllersFromOverview resolves every controller listed in one "show all"
+// envelope's "System Overview" section. storcli2 omits that section when the
+// host has no controllers ("Number of Controllers": 0); that is an empty
+// inventory, not an error, mirroring the logical-volume and physical-drive
+// getters.
+func (s *StorCLI2) controllersFromOverview(controller storcli2.Controller) (
+	[]*raidcontroller.RAIDController,
+	error,
+) {
+	overview, err := utils.UnmarshalToSlice[storcli2SystemOverview](
+		controller.ResponseData, "System Overview",
+	)
+	if err != nil {
+		if errors.Is(err, utils.ErrKeyNotFound) {
+			return nil, nil
 		}
+
+		return nil, errors.Wrap(err, "failed to unmarshal system overview")
+	}
+
+	controllers := make([]*raidcontroller.RAIDController, 0, len(overview))
+
+	for j := range overview {
+		metadata := &raidcontroller.Metadata{ID: overview[j].Ctrl}
+
+		found, err := s.Controller(metadata)
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed to get controller %d", metadata.ID)
+		}
+
+		controllers = append(controllers, found)
 	}
 
 	return controllers, nil

pkg/implementation/controllergetter/storcli2_test.go

@@ -52,6 +52,11 @@ func TestStorCLI2Controllers(t *testing.T) {
 			showAll:     []byte(`{"Controllers":[]}`),
 			expectError: true,
 		},
+		{
+			name:        "no managed controllers",
+			showAll:     storcli2Fixture(t, "all_no_controllers.json"),
+			expectedLen: 0,
+		},
 	}
 
 	for _, tt := range tests {
@@ -81,7 +86,10 @@ func TestStorCLI2Controllers(t *testing.T) {
 
 			require.NoError(t, err)
 			require.Len(t, controllers, tt.expectedLen)
-			assert.Equal(t, 0, controllers[0].ID)
+
+			if tt.expectedLen > 0 {
+				assert.Equal(t, 0, controllers[0].ID)
+			}
 		})
 	}
 }

pkg/implementation/controllergetter/testdata/storcli2/all_no_controllers.json

@@ -0,0 +1,19 @@
+{
+"Controllers":[
+{
+	"Command Status" : {
+		"CLI Version" : "008.0005.0000.0010 Feb 22, 2023",
+		"Operating system" : "Linux4.18.0-553.124.1.el8_10.x86_64",
+		"Status Code" : 0,
+		"Status" : "Success",
+		"Description" : "None"
+	},
+	"Response Data" : {
+		"Number of Controllers" : 0,
+		"Host Name" : "application-node",
+		"Operating System " : "Linux4.18.0-553.124.1.el8_10.x86_64",
+		"SL8 Library Version" : "08.0507.0000"
+	}
+}
+]
+}