consul/connect: fix upstream mesh gateway default mode setting

This PR fixes the API to _not_ set the default mesh gateway mode. Before,
the mode would be set to "none" in Canonicalize, which is incorrect. We
should pass through the empty string so that folks can make use of Consul
service-defaults Config entries to configure the default mode.

api/services.go

@@ -310,13 +310,9 @@ type ConsulMeshGateway struct {
 }
 
 func (c *ConsulMeshGateway) Canonicalize() {
-	if c == nil {
-		return
-	}
-
-	if c.Mode == "" {
-		c.Mode = "none"
-	}
+	// Mode may be empty string, indicating behavior will defer to Consul
+	// service-defaults config entry.
+	return
 }
 
 func (c *ConsulMeshGateway) Copy() *ConsulMeshGateway {

api/services_test.go

@@ -613,13 +613,15 @@ func TestService_ConsulMeshGateway_Canonicalize(t *testing.T) {
 	})
 
 	t.Run("unset mode", func(t *testing.T) {
-		c := &ConsulMeshGateway{
-			Mode: "",
-		}
+		c := &ConsulMeshGateway{Mode: ""}
 		c.Canonicalize()
-		require.Equal(t, &ConsulMeshGateway{
-			Mode: "none",
-		}, c)
+		require.Equal(t, "", c.Mode)
+	})
+
+	t.Run("set mode", func(t *testing.T) {
+		c := &ConsulMeshGateway{Mode: "remote"}
+		c.Canonicalize()
+		require.Equal(t, "remote", c.Mode)
 	})
 }
 

website/content/docs/job-specification/upstreams.mdx

@@ -94,8 +94,8 @@ job "countdash" {
 
 ### `mesh_gateway` Parameters
 
-- `mode` `(string: "default")` - The mode of operation in which to use [Connect Mesh Gateways][mesh_gateways]
-Defaults to the mode as determined by the Consul [service-defaults][service_defaults_mode]
+- `mode` `(string: "")` - The mode of operation in which to use [Connect Mesh Gateways][mesh_gateways].
+  If left unset, the mode will default to the mode as determined by the Consul [service-defaults][service_defaults_mode]
   configuration for the service. Can be configured with the following modes:
   - `local` - In this mode the Connect proxy makes its outbound connection to a
   gateway running in the same datacenter. That gateway is then responsible for