Grafana's Slack webhooks can't be parsed

Hello John,

We faced an error when we tried to connect Grafana slack webhooks to Glip:

json: cannot unmarshal number into Go struct field Field.attachments.fields.value of type string

Here is an example Grafana payload:

{
    "attachments": [
        {
            "color": "#D63232",
            "fallback": "[Alerting] TEST",
            "fields": [
                {
                    "short": true,
                    "title": "server $tag_name replication_lag",
                    "value": 0
                },
                {
                    "short": true,
                    "title": "server $tag_name replication_lag",
                    "value": 0
                },
                {
                    "short": true,
                    "title": "server $tag_name replication_lag",
                    "value": 0
                },
                {
                    "short": true,
                    "title": "server $tag_name replication_lag",
                    "value": 0
                },
                {
                    "short": true,
                    "title": "server $tag_name replication_lag",
                    "value": 0
                },
                {
                    "short": true,
                    "title": "server $tag_name replication_lag",
                    "value": 0
                }
            ],
            "footer": "Grafana v8",
            "footer_icon": "https://grafana.com/assets/img/fav32.png",
            "text": "",
            "title": "[Alerting] TEST",
            "title_link": "https://grafana/",
            "ts": 1643390857
        }
    ],
    "channel": ""
}

As you can see value is an int and not a string as expected.

This probably could be fixed by being more flexible on the expected values:

type Flexval struct {
  Value string `json:value,omitempty`
}

func (flexval *Flexval) UnmarshalJSON(msg []byte) error {
  var f interface{}

  err := json.Unmarshal(msg, &f)
  if (err != nil) {
    panic(err)
  }

  str, ok := f.(string)

  if ok {
    flexval.Value = str
  }

  fl, ok := f.(float64)

  if ok {
    flexval.Value = fmt.Sprintf("%g", fl)
  }

  return nil;
}

type Field struct {
       Title string    `json:"title,omitempty"`
       FlexVal Flexval `json:"value,omitempty"`
       Short bool      `json:"short,omitempty"`
 }

other changes to fix the type + value access

WDYT?

grokify / commonchat

Grafana's Slack webhooks can't be parsed #3