fix(inputs.gnmi): Handle canonical field-name correctly for non-explicit subscriptions (#13332)

plugins/inputs/gnmi/handler.go

@@ -239,29 +239,26 @@ func (h *handler) handleSubscribeResponseUpdate(acc telegraf.Accumulator, respon
 		// Group metrics
 		for k, v := range fields {
 			key := k
-			if len(aliasPath) < len(key) && len(aliasPath) != 0 {
-				// This may not be an exact prefix, due to naming style
-				// conversion on the key.
-				key = key[len(aliasPath)+1:]
-			} else if len(aliasPath) >= len(key) {
-				if h.canonicalFieldNames {
-					// Strip the origin is any for the field names
-					if parts := strings.SplitN(key, ":", 2); len(parts) == 2 {
-						key = parts[1]
-					}
-				} else {
+			if h.canonicalFieldNames {
+				// Strip the origin is any for the field names
+				if parts := strings.SplitN(key, ":", 2); len(parts) == 2 {
+					key = parts[1]
+				}
+			} else {
+				if len(aliasPath) < len(key) && len(aliasPath) != 0 {
+					// This may not be an exact prefix, due to naming style
+					// conversion on the key.
+					key = key[len(aliasPath)+1:]
+				} else if len(aliasPath) >= len(key) {
 					// Otherwise use the last path element as the field key.
 					key = path.Base(key)
-
-					// If there are no elements skip the item; this would be an
-					// invalid message.
-					key = strings.TrimLeft(key, "/.")
-					if key == "" {
-						h.log.Errorf("invalid empty path: %q", k)
-						continue
-					}
 				}
 			}
+			key = strings.TrimLeft(key, "/.")
+			if key == "" {
+				h.log.Errorf("invalid empty path: %q", k)
+				continue
+			}
 			grouper.Add(name, tags, timestamp, key, v)
 		}
 	}

plugins/inputs/gnmi/testcases/canonical_field_names/expected.out

@@ -1 +1 @@
-interfaces,name=eth42,path=openconfig-interfaces:/interfaces/interface,source=127.0.0.1 /interfaces/interface/descr="eth42",/interfaces/interface/config/id=42425u,/interfaces/interface/state/in_pkts=5678u,/interfaces/interface/state/out_pkts=5125u 1673608605875353770
+interfaces,name=eth42,path=openconfig-interfaces:/interfaces/interface,source=127.0.0.1 interfaces/interface/descr="eth42",interfaces/interface/config/id=42425u,interfaces/interface/state/in_pkts=5678u,interfaces/interface/state/out_pkts=5125u 1673608605875353770

plugins/inputs/gnmi/testcases/canonical_field_names/telegraf.conf

@@ -18,12 +18,6 @@
   [[inputs.gnmi.subscription]]
     name              = "interfaces"
     origin            = "openconfig-interfaces"
-    path              = "/interfaces/interface/state/in-pkts"
-    subscription_mode = "sample"
-    sample_interval   = "10s"
-  [[inputs.gnmi.subscription]]
-    name              = "interfaces"
-    origin            = "openconfig-interfaces"
-    path              = "/interfaces/interface/state/out-pkts"
+    path              = "/interfaces/interface/state"
     subscription_mode = "sample"
     sample_interval   = "10s"