deployed-labeler: serialise errors as strings

per golang/go#5161 serializing an `error` object to json emits an empty object; this caused deployed-labeler to emit an empty object when erroring. This commit converts all errors to strings before returning to the user to provide more context.

Author: adrienthebo

plugins/deployed-labeler/main.go

@@ -94,16 +94,19 @@ func main() {
 func (s *server) markDeployedPR(w http.ResponseWriter, req *http.Request) {
 	var commitSHA string
 	var team string
+
 	for k, v := range req.URL.Query() {
 		switch k {
 		case "commit":
 			commitSHA = v[0]
 		case "team":
 			team = v[0]
+
 		default:
 			s.log.Warnf("Unrecognized parameter received: %s", k)
 		}
 	}
+
 	if team == "" || commitSHA == "" {
 
 		var preconditionFailed struct {
@@ -127,16 +130,28 @@ func (s *server) markDeployedPR(w http.ResponseWriter, req *http.Request) {
 		return
 	}
 
+	var errs []error
+
 	switch req.Method {
 	case "GET":
 		var msg struct {
 			PRs struct {
 				Labeled   []string `json:"labeled"`
 				Unlabeled []string `json:"unlabeled"`
 			}
-			Errors []error `json:"errors"`
+			Errors []string `json:"errors"`
+		}
+
+		msg.PRs.Labeled, msg.PRs.Unlabeled, errs = s.handleGetUnmarkedPRs(req.Context(), commitSHA, team)
+
+		msg.Errors = make([]string, 0, len(errs))
+		for _, err := range errs {
+			msg.Errors = append(msg.Errors, err.Error())
+		}
+
+		if len(msg.Errors) > 0 {
+			w.WriteHeader(http.StatusUnprocessableEntity)
 		}
-		msg.PRs.Labeled, msg.PRs.Unlabeled, msg.Errors = s.handleGetUnmarkedPRs(req.Context(), commitSHA, team)
 
 		enc := json.NewEncoder(w)
 		enc.SetIndent("", "  ")
@@ -150,8 +165,18 @@ func (s *server) markDeployedPR(w http.ResponseWriter, req *http.Request) {
 			} `json:"deployedPRs"`
 			Errors []error `json:"errors"`
 		}
+
 		msg.DeployedPRs.Team, msg.DeployedPRs.All, msg.Errors = s.handleMarkDeployedPRs(req.Context(), commitSHA, team)
 
+		msg.Errors = make([]string, 0, len(errs))
+		for _, err := range errs {
+			msg.Errors = append(msg.Errors, err.Error())
+		}
+
+		if len(msg.Errors) > 0 {
+			w.WriteHeader(http.StatusUnprocessableEntity)
+		}
+
 		enc := json.NewEncoder(w)
 		enc.SetIndent("", "  ")
 		enc.Encode(msg)