api: Return empty list instead of nil

command/agent/agent_endpoint.go

@@ -96,6 +96,14 @@ func (s *HTTPServer) AgentServices(resp http.ResponseWriter, req *http.Request)
 	if err := s.agent.filterServices(token, &services); err != nil {
 		return nil, err
 	}
+
+	// Use empty list instead of nil
+	for _, s := range services {
+		if s.Tags == nil {
+			s.Tags = make([]string, 0)
+		}
+	}
+
 	return services, nil
 }
 
@@ -108,6 +116,14 @@ func (s *HTTPServer) AgentChecks(resp http.ResponseWriter, req *http.Request) (i
 	if err := s.agent.filterChecks(token, &checks); err != nil {
 		return nil, err
 	}
+
+	// Use empty list instead of nil
+	for _, c := range checks {
+		if c.ServiceTags == nil {
+			c.ServiceTags = make([]string, 0)
+		}
+	}
+
 	return checks, nil
 }
 

command/agent/catalog_endpoint.go

@@ -96,6 +96,11 @@ func (s *HTTPServer) CatalogServices(resp http.ResponseWriter, req *http.Request
 	if err := s.agent.RPC("Catalog.ListServices", &args, &out); err != nil {
 		return nil, err
 	}
+
+	// Use empty map instead of nil
+	if out.Services == nil {
+		out.Services = make(structs.Services, 0)
+	}
 	return out.Services, nil
 }
 
@@ -135,6 +140,11 @@ func (s *HTTPServer) CatalogServiceNodes(resp http.ResponseWriter, req *http.Req
 	if out.ServiceNodes == nil {
 		out.ServiceNodes = make(structs.ServiceNodes, 0)
 	}
+	for _, s := range out.ServiceNodes {
+		if s.ServiceTags == nil {
+			s.ServiceTags = make([]string, 0)
+		}
+	}
 	return out.ServiceNodes, nil
 }
 
@@ -163,5 +173,13 @@ func (s *HTTPServer) CatalogNodeServices(resp http.ResponseWriter, req *http.Req
 		translateAddresses(s.agent.config, args.Datacenter, out.NodeServices.Node)
 	}
 
+	// Use empty list instead of nil
+	if out.NodeServices != nil {
+		for _, s := range out.NodeServices.Services {
+			if s.Tags == nil {
+				s.Tags = make([]string, 0)
+			}
+		}
+	}
 	return out.NodeServices, nil
 }

command/agent/health_endpoint.go

@@ -37,6 +37,11 @@ func (s *HTTPServer) HealthChecksInState(resp http.ResponseWriter, req *http.Req
 	if out.HealthChecks == nil {
 		out.HealthChecks = make(structs.HealthChecks, 0)
 	}
+	for _, c := range out.HealthChecks {
+		if c.ServiceTags == nil {
+			c.ServiceTags = make([]string, 0)
+		}
+	}
 	return out.HealthChecks, nil
 }
 
@@ -66,6 +71,11 @@ func (s *HTTPServer) HealthNodeChecks(resp http.ResponseWriter, req *http.Reques
 	if out.HealthChecks == nil {
 		out.HealthChecks = make(structs.HealthChecks, 0)
 	}
+	for _, c := range out.HealthChecks {
+		if c.ServiceTags == nil {
+			c.ServiceTags = make([]string, 0)
+		}
+	}
 	return out.HealthChecks, nil
 }
 
@@ -97,6 +107,11 @@ func (s *HTTPServer) HealthServiceChecks(resp http.ResponseWriter, req *http.Req
 	if out.HealthChecks == nil {
 		out.HealthChecks = make(structs.HealthChecks, 0)
 	}
+	for _, c := range out.HealthChecks {
+		if c.ServiceTags == nil {
+			c.ServiceTags = make([]string, 0)
+		}
+	}
 	return out.HealthChecks, nil
 }
 
@@ -140,6 +155,9 @@ func (s *HTTPServer) HealthServiceNodes(resp http.ResponseWriter, req *http.Requ
 	translateAddresses(s.agent.config, args.Datacenter, out.Nodes)
 
 	// Use empty list instead of nil
+	if out.Nodes == nil {
+		out.Nodes = make(structs.CheckServiceNodes, 0)
+	}
 	for i := range out.Nodes {
 		// TODO (slackpad) It's lame that this isn't a slice of pointers
 		// but it's not a well-scoped change to fix this. We should
@@ -147,11 +165,15 @@ func (s *HTTPServer) HealthServiceNodes(resp http.ResponseWriter, req *http.Requ
 		if out.Nodes[i].Checks == nil {
 			out.Nodes[i].Checks = make(structs.HealthChecks, 0)
 		}
+		for _, c := range out.Nodes[i].Checks {
+			if c.ServiceTags == nil {
+				c.ServiceTags = make([]string, 0)
+			}
+		}
+		if out.Nodes[i].Service != nil && out.Nodes[i].Service.Tags == nil {
+			out.Nodes[i].Service.Tags = make([]string, 0)
+		}
 	}
-	if out.Nodes == nil {
-		out.Nodes = make(structs.CheckServiceNodes, 0)
-	}
-
 	return out.Nodes, nil
 }