wmi: improve error handling

pkg/wmi/wmi.go

@@ -15,27 +15,37 @@ type Data struct {
 }
 
 func Query(query string) (querydata [][]Data, err error) {
-	var ret [][]Data
-
 	err = ole.CoInitialize(0)
 	if err != nil {
-		return nil, fmt.Errorf("check_service: couldn't initialize COM connection: %s", err.Error())
+		return nil, fmt.Errorf("wmi: ole.CoInitialize failed: %s", err.Error())
 	}
 	defer ole.CoUninitialize()
 
-	unknown, _ := oleutil.CreateObject("WbemScripting.SWbemLocator")
+	unknown, err := oleutil.CreateObject("WbemScripting.SWbemLocator")
+	if err != nil {
+		return nil, fmt.Errorf("wmi: CreateObject WbemScripting.SWbemLocator failed: %s", err.Error())
+	}
 	defer unknown.Release()
 
-	wmi, _ := unknown.QueryInterface(ole.IID_IDispatch)
+	wmi, err := unknown.QueryInterface(ole.IID_IDispatch)
+	if err != nil {
+		return nil, fmt.Errorf("wmi: QueryInterface ole.IID_IDispatch failed: %s", err.Error())
+	}
 	defer wmi.Release()
 
 	// service is a SWbemServices
-	serviceRaw, _ := oleutil.CallMethod(wmi, "ConnectServer")
+	serviceRaw, err := oleutil.CallMethod(wmi, "ConnectServer")
+	if err != nil {
+		return nil, fmt.Errorf("wmi: CallMethod ConnectServer failed: %s", err.Error())
+	}
 	service := serviceRaw.ToIDispatch()
 	defer service.Release()
 
 	// result is a SWBemObjectSet
-	resultRaw, _ := oleutil.CallMethod(service, "ExecQuery", query)
+	resultRaw, err := oleutil.CallMethod(service, "ExecQuery", query)
+	if err != nil {
+		return nil, fmt.Errorf("wmi: CallMethod ExecQuery failed: %s", err.Error())
+	}
 	result := resultRaw.ToIDispatch()
 	defer result.Release()
 
@@ -45,47 +55,47 @@ func Query(query string) (querydata [][]Data, err error) {
 	re := regexp.MustCompile(`\w+\s+((?:\w+\s*,\s*)*\w+)`)
 	values := strings.Split(re.FindStringSubmatch(query)[1], ",")
 
+	ret := make([][]Data, 0)
 	for i := 0; i < count; i++ {
 		// item is a SWbemObject, but really a Win32_Process
-		err = func() error {
-			itemRaw, err := oleutil.CallMethod(result, "ItemIndex", i)
-			if err != nil {
-				return fmt.Errorf("wmi call failed: %s", err.Error())
-			}
-			item := itemRaw.ToIDispatch()
-			defer item.Release()
-
-			var obj []Data
-
-			for _, val := range values {
-				var value string
-				property, err := oleutil.GetProperty(item, strings.TrimSpace(val))
-				if err != nil {
-					return fmt.Errorf("WMI: error getting property from item (%s)", err.Error())
-				}
-				if property.Value() == nil {
-					value = ""
-				} else {
-					switch t := property.Value().(type) {
-					case int32:
-						value = fmt.Sprintf("%d", t)
-					default:
-						value = property.ToString()
-					}
-				}
-				obj = append(obj, Data{Key: strings.TrimSpace(val), Value: value})
-			}
+		obj, err := processResult(values, result, i)
+		if err != nil {
+			return nil, err
+		}
+		ret = append(ret, obj)
+	}
 
-			ret = append(ret, obj)
+	return ret, nil
+}
 
-			return nil
-		}()
+func processResult(values []string, result *ole.IDispatch, i int) (obj []Data, err error) {
+	itemRaw, err := oleutil.CallMethod(result, "ItemIndex", i)
+	if err != nil {
+		return nil, fmt.Errorf("oleutil.CallMethod failed: %s", err.Error())
+	}
+	item := itemRaw.ToIDispatch()
+	defer item.Release()
+
+	for _, val := range values {
+		var value string
+		property, err := oleutil.GetProperty(item, strings.TrimSpace(val))
 		if err != nil {
-			return nil, fmt.Errorf("wmi error: %s", err.Error())
+			return nil, fmt.Errorf("oleutil.GetProperty failed for item: %s (%s)", val, err.Error())
 		}
+		if property.Value() == nil {
+			value = ""
+		} else {
+			switch t := property.Value().(type) {
+			case int32:
+				value = fmt.Sprintf("%d", t)
+			default:
+				value = property.ToString()
+			}
+		}
+		obj = append(obj, Data{Key: strings.TrimSpace(val), Value: value})
 	}
 
-	return ret, nil
+	return obj, nil
 }
 
 func ResultToMap(queryResult [][]Data) []map[string]string {