ec2/ec2test: handle "tag:" filter for volumes

Handle the "tag:key=value" type filter for
volumes. This is required for Juju to be able
to list volumes belonging to an environment.

ec2/ec2test/server.go

@@ -2198,6 +2198,10 @@ func (v *volume) matchAttr(attr, value string) (ok bool, err error) {
 	if strings.HasPrefix(attr, "attachment.") {
 		return false, fmt.Errorf("%q filter is not implemented", attr)
 	}
+	if strings.HasPrefix(attr, "tag:") {
+		key := attr[len("tag:"):]
+		return matchTag(v.Tags, key, value), nil
+	}
 	switch attr {
 	case "volume-type":
 		return v.VolumeType == value, nil
@@ -2787,3 +2791,12 @@ func fatalf(statusCode int, code string, f string, a ...interface{}) {
 		Message:    fmt.Sprintf(f, a...),
 	})
 }
+
+func matchTag(tags []ec2.Tag, key, value string) bool {
+	for _, tag := range tags {
+		if tag.Key == key {
+			return tag.Value == value
+		}
+	}
+	return false
+}

ec2/volumes_test.go

@@ -223,6 +223,41 @@ func (s *ServerTests) TestVolumes(c *C) {
 	assertVolume(c, list.Volumes[0], id2, vol2.VolumeType, vol2.AvailZone, 101, vol2.IOPS)
 }
 
+func (s *ServerTests) TestVolumesTagFilter(c *C) {
+	createVolume := func() string {
+		resp, err := s.ec2.CreateVolume(ec2.CreateVolume{
+			AvailZone:  "us-east-1b",
+			VolumeType: "standard",
+			VolumeSize: 1,
+		})
+		c.Assert(err, IsNil)
+		return resp.Id
+	}
+	destroyVolume := func(id string) {
+		_, err := s.ec2.DeleteVolume(id)
+		c.Assert(err, IsNil)
+	}
+
+	volId1 := createVolume()
+	defer destroyVolume(volId1)
+	volId2 := createVolume()
+	defer destroyVolume(volId2)
+
+	filter := ec2.NewFilter()
+	filter.Add("tag:key", "value")
+	resp, err := s.ec2.Volumes(nil, filter)
+	c.Assert(err, IsNil)
+	c.Assert(resp.Volumes, HasLen, 0)
+
+	_, err = s.ec2.CreateTags([]string{volId1}, []ec2.Tag{{"key", "value"}})
+	c.Assert(err, IsNil)
+
+	resp, err = s.ec2.Volumes(nil, filter)
+	c.Assert(err, IsNil)
+	c.Assert(resp.Volumes, HasLen, 1)
+	c.Assert(resp.Volumes[0].Id, Equals, volId1)
+}
+
 func assertVolume(c *C, obtained ec2.Volume, expectId, expectType, availZone string, expectSize int, expectIOPS int64) {
 	if expectId != "" {
 		c.Check(obtained.Id, Equals, expectId)