fix: apply tag:<key> filters to DescribeTags rows

spinifex/handlers/ec2/tags/service_impl.go

@@ -344,6 +344,9 @@ func (s *TagsServiceImpl) DescribeTags(ctx context.Context, input *ec2.DescribeT
 			if !filterutil.MatchesAny(filters["tag-key"], key) || !filterutil.MatchesAny(filters["tag-value"], value) {
 				continue
 			}
+			if !rowMatchesTagFilters(filters, key, value) {
+				continue
+			}
 
 			tags = append(tags, &ec2.TagDescription{
 				ResourceId:   aws.String(resourceID),
@@ -361,6 +364,22 @@ func (s *TagsServiceImpl) DescribeTags(ctx context.Context, input *ec2.DescribeT
 	}, nil
 }
 
+// rowMatchesTagFilters applies each tag:<key> filter to one tag row, as
+// tag-key and tag-value are applied here: the row must be that key, with a
+// value the filter names.
+func rowMatchesTagFilters(filters map[string][]string, key, value string) bool {
+	for name, values := range filters {
+		tagKey, ok := strings.CutPrefix(name, "tag:")
+		if !ok {
+			continue
+		}
+		if key != tagKey || !filterutil.MatchesAny(values, value) {
+			return false
+		}
+	}
+	return true
+}
+
 // DeleteTags removes tags from the specified resources.
 func (s *TagsServiceImpl) DeleteTags(ctx context.Context, input *ec2.DeleteTagsInput, accountID string) (*ec2.DeleteTagsOutput, error) {
 	if input == nil {

spinifex/handlers/ec2/tags/service_impl_test.go

@@ -322,6 +322,41 @@ func TestDescribeTags_FilterByTagKeyAndTagValue(t *testing.T) {
 	assert.Empty(t, describe("tag-value", "zz-awsdiff-none"))
 }
 
+// TestDescribeTags_FilterByTagKeyName checks that a tag:<key> filter selects
+// the matching tag row, and only rows of resources that carry it.
+func TestDescribeTags_FilterByTagKeyName(t *testing.T) {
+	svc, _ := setupTestTagsService(t)
+
+	for id, run := range map[string]string{"subnet-test1": "run-1", "subnet-test2": "run-2"} {
+		_, err := svc.CreateTags(context.Background(), &ec2.CreateTagsInput{
+			Resources: []*string{aws.String(id)},
+			Tags: []*ec2.Tag{
+				{Key: aws.String("env"), Value: aws.String("prod")},
+				{Key: aws.String("awsdiff"), Value: aws.String(run)},
+			},
+		}, testAccountID)
+		require.NoError(t, err)
+	}
+
+	result, err := svc.DescribeTags(context.Background(), &ec2.DescribeTagsInput{
+		Filters: []*ec2.Filter{
+			{Name: aws.String("resource-type"), Values: []*string{aws.String("subnet")}},
+			{Name: aws.String("tag:awsdiff"), Values: []*string{aws.String("run-1")}},
+		},
+	}, testAccountID)
+	require.NoError(t, err)
+	require.Len(t, result.Tags, 1)
+	assert.Equal(t, "subnet-test1", aws.StringValue(result.Tags[0].ResourceId))
+	assert.Equal(t, "awsdiff", aws.StringValue(result.Tags[0].Key))
+	assert.Equal(t, "run-1", aws.StringValue(result.Tags[0].Value))
+
+	result, err = svc.DescribeTags(context.Background(), &ec2.DescribeTagsInput{
+		Filters: []*ec2.Filter{{Name: aws.String("tag:awsdiff"), Values: []*string{aws.String("zz-awsdiff-none")}}},
+	}, testAccountID)
+	require.NoError(t, err)
+	assert.Empty(t, result.Tags)
+}
+
 // TestDescribeTags_Empty tests listing tags when none exist.
 func TestDescribeTags_Empty(t *testing.T) {
 	svc, _ := setupTestTagsService(t)