Static analyzer for httputil.HandleError calls (#16134)

**What type of PR is this?**

Tooling

**What does the PR do?**

Every call to `httputil.HandleError` must be followed by a `return`
statement. It's easy to miss this during reviews, so having a static
analyzer that enforces this will make our life easier.

**Acknowledgements**

- [x] I have read
[CONTRIBUTING.md](https://github.com/prysmaticlabs/prysm/blob/develop/CONTRIBUTING.md).
- [x] I have included a uniquely named [changelog fragment
file](https://github.com/prysmaticlabs/prysm/blob/develop/CONTRIBUTING.md#maintaining-changelogmd).
- [x] I have added a description with sufficient context for reviewers
to understand this PR.
- [x] I have tested that my changes work as expected and I added a
testing plan to the PR description (if applicable).

---------

Co-authored-by: james-prysm <90280386+james-prysm@users.noreply.github.com>

beacon-chain/rpc/eth/light-client/handlers.go

@@ -116,6 +116,7 @@ func (s *Server) GetLightClientUpdatesByRange(w http.ResponseWriter, req *http.R
 		for _, update := range updates {
 			if ctx.Err() != nil {
 				httputil.HandleError(w, "Context error: "+ctx.Err().Error(), http.StatusInternalServerError)
+				return
 			}
 
 			updateSlot := update.AttestedHeader().Beacon().Slot
@@ -131,12 +132,15 @@ func (s *Server) GetLightClientUpdatesByRange(w http.ResponseWriter, req *http.R
 			chunkLength = ssz.MarshalUint64(chunkLength, uint64(len(updateSSZ)+4))
 			if _, err := w.Write(chunkLength); err != nil {
 				httputil.HandleError(w, "Could not write chunk length: "+err.Error(), http.StatusInternalServerError)
+				return
 			}
 			if _, err := w.Write(updateEntry.ForkDigest[:]); err != nil {
 				httputil.HandleError(w, "Could not write fork digest: "+err.Error(), http.StatusInternalServerError)
+				return
 			}
 			if _, err := w.Write(updateSSZ); err != nil {
 				httputil.HandleError(w, "Could not write update SSZ: "+err.Error(), http.StatusInternalServerError)
+				return
 			}
 		}
 	} else {
@@ -145,6 +149,7 @@ func (s *Server) GetLightClientUpdatesByRange(w http.ResponseWriter, req *http.R
 		for _, update := range updates {
 			if ctx.Err() != nil {
 				httputil.HandleError(w, "Context error: "+ctx.Err().Error(), http.StatusInternalServerError)
+				return
 			}
 
 			updateJson, err := structs.LightClientUpdateFromConsensus(update)

beacon-chain/rpc/eth/node/handlers.go

@@ -132,6 +132,7 @@ func (s *Server) GetHealth(w http.ResponseWriter, r *http.Request) {
 	optimistic, err := s.OptimisticModeFetcher.IsOptimistic(ctx)
 	if err != nil {
 		httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+		return
 	}
 	if s.SyncChecker.Synced() && !optimistic {
 		return

beacon-chain/rpc/eth/validator/handlers.go

@@ -1103,7 +1103,8 @@ func (s *Server) GetProposerDuties(w http.ResponseWriter, r *http.Request) {
 		httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
 		return
 	}
-	if !sortProposerDuties(w, duties) {
+	if err = sortProposerDuties(duties); err != nil {
+		httputil.HandleError(w, "Could not sort proposer duties: "+err.Error(), http.StatusInternalServerError)
 		return
 	}
 
@@ -1447,22 +1448,20 @@ func syncCommitteeDutiesAndVals(
 	return duties, vals, nil
 }
 
-func sortProposerDuties(w http.ResponseWriter, duties []*structs.ProposerDuty) bool {
-	ok := true
+func sortProposerDuties(duties []*structs.ProposerDuty) error {
+	var err error
 	sort.Slice(duties, func(i, j int) bool {
-		si, err := strconv.ParseUint(duties[i].Slot, 10, 64)
-		if err != nil {
-			httputil.HandleError(w, "Could not parse slot: "+err.Error(), http.StatusInternalServerError)
-			ok = false
+		si, parseErr := strconv.ParseUint(duties[i].Slot, 10, 64)
+		if parseErr != nil {
+			err = errors.Wrap(parseErr, "could not parse slot")
 			return false
 		}
-		sj, err := strconv.ParseUint(duties[j].Slot, 10, 64)
-		if err != nil {
-			httputil.HandleError(w, "Could not parse slot: "+err.Error(), http.StatusInternalServerError)
-			ok = false
+		sj, parseErr := strconv.ParseUint(duties[j].Slot, 10, 64)
+		if parseErr != nil {
+			err = errors.Wrap(parseErr, "could not parse slot")
 			return false
 		}
 		return si < sj
 	})
-	return ok
+	return err
 }