Prioritize method matching

Problem: A recent clarification in the gateway API stated that methods are prioritized higher than headers when matching. We were not abiding by this order.

Solution: Check for methods to prioritize rules before we check headers.

internal/state/dataplane/sort.go

@@ -24,6 +24,7 @@ Precedence must be given to the Rule with the largest number of (Continuing on t
 - Characters in a matching non-wildcard hostname.
 - Characters in a matching hostname.
 - Characters in a matching path.
+- Method match.
 - Header matches.
 - Query param matches.
 
@@ -43,16 +44,25 @@ func higherPriority(rule1, rule2 MatchRule) bool {
 	match1 := rule1.GetMatch()
 	match2 := rule2.GetMatch()
 
-	// If both matches exists then compare the number of header matches
-	// The match with the largest number of header matches wins
+	// Compare if a method exists on one of the matches but not the other.
+	// The match with the method specified wins.
+	if match1.Method != nil && match2.Method == nil {
+		return true
+	}
+	if match2.Method != nil && match1.Method == nil {
+		return false
+	}
+
+	// Compare the number of header matches.
+	// The match with the largest number of header matches wins.
 	l1 := len(match1.Headers)
 	l2 := len(match2.Headers)
 
 	if l1 != l2 {
 		return l1 > l2
 	}
-	// If the number of headers is equal then compare the number of query param matches
-	// The match with the most query param matches wins
+	// If the number of headers is equal then compare the number of query param matches.
+	// The match with the most query param matches wins.
 	l1 = len(match1.QueryParams)
 	l2 = len(match2.QueryParams)
 

internal/state/dataplane/sort_test.go

@@ -77,6 +77,12 @@ func TestSort(t *testing.T) {
 			},
 		},
 	}
+	methodMatch := v1beta1.HTTPRouteMatch{
+		Path: &v1beta1.HTTPPathMatch{
+			Value: helpers.GetStringPointer("/path"),
+		},
+		Method: helpers.GetPointer(v1beta1.HTTPMethodPost),
+	}
 
 	hr1 := v1beta1.HTTPRoute{
 		ObjectMeta: metav1.ObjectMeta{
@@ -96,6 +102,7 @@ func TestSort(t *testing.T) {
 					Matches: []v1beta1.HTTPRouteMatch{
 						twoHeaderOneParamMatch, // tie decided on params
 						threeHeaderMatch,       // tie decided on headers
+						methodMatch,            // tie decided on method
 					},
 				},
 			},
@@ -153,6 +160,11 @@ func TestSort(t *testing.T) {
 			RuleIdx:  2,
 			Source:   &hr1,
 		},
+		{
+			MatchIdx: 2, // methodMatch
+			RuleIdx:  2,
+			Source:   &hr1,
+		},
 		{
 			MatchIdx: 0, // twoHeaderMatch / later timestamp / test/hr2
 			RuleIdx:  0,
@@ -166,6 +178,11 @@ func TestSort(t *testing.T) {
 	}
 
 	sortedRoutes := []MatchRule{
+		{
+			MatchIdx: 2, // methodMatch
+			RuleIdx:  2,
+			Source:   &hr1,
+		},
 		{
 			MatchIdx: 1, // threeHeaderMatch
 			RuleIdx:  2,