Backport of connect: Add support for ConsulResolver to specifies a filter expression into release/1.14.x (#15800)

* backport of commit b73068cdf1
* manual cherry pick

Co-authored-by: Pier-Luc Caron-St-Pierre <pier-luc.caronst-pierre@hashicorp.com>

.changelog/15659.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+connect: Add support for ConsulResolver to specifies a filter expression
+```

connect/resolver.go

@@ -78,6 +78,9 @@ type ConsulResolver struct {
 
 	// Datacenter to resolve in, empty indicates agent's local DC.
 	Datacenter string
+
+	// Specifies the expression used to filter the queries results prior to returning the data.
+	Filter string
 }
 
 // Resolve performs service discovery against the local Consul agent and returns
@@ -173,6 +176,7 @@ func (cr *ConsulResolver) queryOptions(ctx context.Context) *api.QueryOptions {
 
 		// For prepared queries
 		Connect: true,
+		Filter:  cr.Filter,
 	}
 	return q.WithContext(ctx)
 }

connect/resolver_test.go

@@ -68,6 +68,9 @@ func TestConsulResolver_Resolve(t *testing.T) {
 		Proxy: &api.AgentServiceConnectProxyConfig{
 			DestinationServiceName: "web",
 		},
+		Meta: map[string]string{
+			"MetaKey": "MetaValue",
+		},
 	}
 	err = client.Agent().ServiceRegister(regProxy)
 	require.Nil(t, err)
@@ -75,6 +78,7 @@ func TestConsulResolver_Resolve(t *testing.T) {
 	// And another proxy so we can test handling with multiple endpoints returned
 	regProxy.Port = 9091
 	regProxy.ID = "web-proxy-2"
+	regProxy.Meta = map[string]string{}
 	err = client.Agent().ServiceRegister(regProxy)
 	require.Nil(t, err)
 
@@ -110,6 +114,7 @@ func TestConsulResolver_Resolve(t *testing.T) {
 		Name       string
 		Type       int
 		Datacenter string
+		Filter     string
 	}
 	tests := []struct {
 		name        string
@@ -145,6 +150,32 @@ func TestConsulResolver_Resolve(t *testing.T) {
 			wantCertURI: connect.TestSpiffeIDServiceWithHost(t, "db", ""),
 			wantErr:     false,
 		},
+		{
+			name: "service discovery with filter",
+			fields: fields{
+				Namespace: "default",
+				Name:      "web",
+				Type:      ConsulResolverTypeService,
+				Filter:    "Service.Meta[`MetaKey`] == `MetaValue`",
+			},
+			// Want empty host since we don't enforce trust domain outside of TLS and
+			// don't need to load the current one this way.
+			wantCertURI: connect.TestSpiffeIDServiceWithHost(t, "web", ""),
+			wantErr:     false,
+			addrs: []string{
+				agent.Config.AdvertiseAddrLAN.String() + ":9090",
+			},
+		},
+		{
+			name: "service discovery with filter",
+			fields: fields{
+				Namespace: "default",
+				Name:      "web",
+				Type:      ConsulResolverTypeService,
+				Filter:    "`AnotherMetaValue` in Service.Meta.MetaKey",
+			},
+			wantErr: true,
+		},
 		{
 			name: "Bad Type errors",
 			fields: fields{
@@ -206,6 +237,7 @@ func TestConsulResolver_Resolve(t *testing.T) {
 				Name:       tt.fields.Name,
 				Type:       tt.fields.Type,
 				Datacenter: tt.fields.Datacenter,
+				Filter:     tt.fields.Filter,
 			}
 			// WithCancel just to have a cancel func in scope to assign in the if
 			// clause.