map bool -> map struct{} (#2386)

This clear out the remaining map[x]bool usage and moves the bool to an
empty struct.

Two note worthy other changes:

* EnableChaos in the server is now also exported to make it show up in
  the documentation.
* The auto plugin is left as is, because there the boolean is
  explicitaly set to false to signal 'to-be-deleted' and the key is left
  as-is.

Signed-off-by: Miek Gieben <miek@miek.nl>

7 files changed, 49 insertions, 47 deletions

diff --git a/plugin/kubernetes/xfr_test.go b/plugin/kubernetes/xfr_test.go
index dc6404c0c..db55aa8ed 100644
--- a/plugin/kubernetes/xfr_test.go
+++ b/plugin/kubernetes/xfr_test.go
@@ -129,9 +129,9 @@ func TestKubernetesXFRNotAllowed(t *testing.T) {
 
 // difference shows what we're missing when comparing two RR slices
 func difference(testRRs []dns.RR, gotRRs []dns.RR) []dns.RR {
-	expectedRRs := map[string]bool{}
+	expectedRRs := map[string]struct{}{}
 	for _, rr := range testRRs {
-		expectedRRs[rr.String()] = true
+		expectedRRs[rr.String()] = struct{}{}
 	}
 
 	foundRRs := []dns.RR{}
diff --git a/plugin/log/log.go b/plugin/log/log.go
index d963a134f..327bbf032 100644
--- a/plugin/log/log.go
+++ b/plugin/log/log.go
@@ -55,7 +55,9 @@ func (l Logger) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
 		class := response.Classify(tpe)
 		// If we don't set up a class in config, the default "all" will be added
 		// and we shouldn't have an empty rule.Class.
-		if rule.Class[response.All] || rule.Class[class] {
+		_, ok := rule.Class[response.All]
+		_, ok1 := rule.Class[class]
+		if ok || ok1 {
 			rep := replacer.New(ctx, r, rrw, CommonLogEmptyValue)
 			clog.Infof(rep.Replace(rule.Format))
 		}
@@ -72,7 +74,7 @@ func (l Logger) Name() string { return "log" }
 // Rule configures the logging plugin.
 type Rule struct {
 	NameScope string
-	Class     map[response.Class]bool
+	Class     map[response.Class]struct{}
 	Format    string
 }
 
diff --git a/plugin/log/log_test.go b/plugin/log/log_test.go
index 6d74f23ad..2de633aa5 100644
--- a/plugin/log/log_test.go
+++ b/plugin/log/log_test.go
@@ -21,7 +21,7 @@ func TestLoggedStatus(t *testing.T) {
 	rule := Rule{
 		NameScope: ".",
 		Format:    DefaultLogFormat,
-		Class:     map[response.Class]bool{response.All: true},
+		Class:     map[response.Class]struct{}{response.All: struct{}{}},
 	}
 
 	var f bytes.Buffer
@@ -53,7 +53,7 @@ func TestLoggedClassDenial(t *testing.T) {
 	rule := Rule{
 		NameScope: ".",
 		Format:    DefaultLogFormat,
-		Class:     map[response.Class]bool{response.Denial: true},
+		Class:     map[response.Class]struct{}{response.Denial: struct{}{}},
 	}
 
 	var f bytes.Buffer
@@ -82,7 +82,7 @@ func TestLoggedClassError(t *testing.T) {
 	rule := Rule{
 		NameScope: ".",
 		Format:    DefaultLogFormat,
-		Class:     map[response.Class]bool{response.Error: true},
+		Class:     map[response.Class]struct{}{response.Error: struct{}{}},
 	}
 
 	var f bytes.Buffer
diff --git a/plugin/log/setup.go b/plugin/log/setup.go
index c3c1af4ca..4a2afceda 100644
--- a/plugin/log/setup.go
+++ b/plugin/log/setup.go
@@ -40,13 +40,13 @@ func logParse(c *caddy.Controller) ([]Rule, error) {
 			rules = append(rules, Rule{
 				NameScope: ".",
 				Format:    DefaultLogFormat,
-				Class:     make(map[response.Class]bool),
+				Class:     make(map[response.Class]struct{}),
 			})
 		} else if len(args) == 1 {
 			rules = append(rules, Rule{
 				NameScope: dns.Fqdn(args[0]),
 				Format:    DefaultLogFormat,
-				Class:     make(map[response.Class]bool),
+				Class:     make(map[response.Class]struct{}),
 			})
 		} else {
 			// Name scope, and maybe a format specified
@@ -64,7 +64,7 @@ func logParse(c *caddy.Controller) ([]Rule, error) {
 			rules = append(rules, Rule{
 				NameScope: dns.Fqdn(args[0]),
 				Format:    format,
-				Class:     make(map[response.Class]bool),
+				Class:     make(map[response.Class]struct{}),
 			})
 		}
 
@@ -82,14 +82,14 @@ func logParse(c *caddy.Controller) ([]Rule, error) {
 					if err != nil {
 						return nil, err
 					}
-					rules[len(rules)-1].Class[cls] = true
+					rules[len(rules)-1].Class[cls] = struct{}{}
 				}
 			default:
 				return nil, c.ArgErr()
 			}
 		}
 		if len(rules[len(rules)-1].Class) == 0 {
-			rules[len(rules)-1].Class[response.All] = true
+			rules[len(rules)-1].Class[response.All] = struct{}{}
 		}
 	}
 
diff --git a/plugin/log/setup_test.go b/plugin/log/setup_test.go
index bf2ac3c3d..3c65c1c85 100644
--- a/plugin/log/setup_test.go
+++ b/plugin/log/setup_test.go
@@ -18,42 +18,42 @@ func TestLogParse(t *testing.T) {
 		{`log`, false, []Rule{{
 			NameScope: ".",
 			Format:    DefaultLogFormat,
-			Class:     map[response.Class]bool{response.All: true},
+			Class:     map[response.Class]struct{}{response.All: struct{}{}},
 		}}},
 		{`log example.org`, false, []Rule{{
 			NameScope: "example.org.",
 			Format:    DefaultLogFormat,
-			Class:     map[response.Class]bool{response.All: true},
+			Class:     map[response.Class]struct{}{response.All: struct{}{}},
 		}}},
 		{`log example.org. {common}`, false, []Rule{{
 			NameScope: "example.org.",
 			Format:    CommonLogFormat,
-			Class:     map[response.Class]bool{response.All: true},
+			Class:     map[response.Class]struct{}{response.All: struct{}{}},
 		}}},
 		{`log example.org {combined}`, false, []Rule{{
 			NameScope: "example.org.",
 			Format:    CombinedLogFormat,
-			Class:     map[response.Class]bool{response.All: true},
+			Class:     map[response.Class]struct{}{response.All: struct{}{}},
 		}}},
 		{`log example.org.
 		log example.net {combined}`, false, []Rule{{
 			NameScope: "example.org.",
 			Format:    DefaultLogFormat,
-			Class:     map[response.Class]bool{response.All: true},
+			Class:     map[response.Class]struct{}{response.All: struct{}{}},
 		}, {
 			NameScope: "example.net.",
 			Format:    CombinedLogFormat,
-			Class:     map[response.Class]bool{response.All: true},
+			Class:     map[response.Class]struct{}{response.All: struct{}{}},
 		}}},
 		{`log example.org {host}
 			  log example.org {when}`, false, []Rule{{
 			NameScope: "example.org.",
 			Format:    "{host}",
-			Class:     map[response.Class]bool{response.All: true},
+			Class:     map[response.Class]struct{}{response.All: struct{}{}},
 		}, {
 			NameScope: "example.org.",
 			Format:    "{when}",
-			Class:     map[response.Class]bool{response.All: true},
+			Class:     map[response.Class]struct{}{response.All: struct{}{}},
 		}}},
 
 		{`log example.org {
@@ -61,28 +61,28 @@ func TestLogParse(t *testing.T) {
 			}`, false, []Rule{{
 			NameScope: "example.org.",
 			Format:    CommonLogFormat,
-			Class:     map[response.Class]bool{response.All: true},
+			Class:     map[response.Class]struct{}{response.All: struct{}{}},
 		}}},
 		{`log example.org {
 			class denial
 		}`, false, []Rule{{
 			NameScope: "example.org.",
 			Format:    CommonLogFormat,
-			Class:     map[response.Class]bool{response.Denial: true},
+			Class:     map[response.Class]struct{}{response.Denial: struct{}{}},
 		}}},
 		{`log {
 			class denial
 		}`, false, []Rule{{
 			NameScope: ".",
 			Format:    CommonLogFormat,
-			Class:     map[response.Class]bool{response.Denial: true},
+			Class:     map[response.Class]struct{}{response.Denial: struct{}{}},
 		}}},
 		{`log {
 			class denial error
 		}`, false, []Rule{{
 			NameScope: ".",
 			Format:    CommonLogFormat,
-			Class:     map[response.Class]bool{response.Denial: true, response.Error: true},
+			Class:     map[response.Class]struct{}{response.Denial: struct{}{}, response.Error: struct{}{}},
 		}}},
 		{`log {
 			class denial
@@ -90,7 +90,7 @@ func TestLogParse(t *testing.T) {
 		}`, false, []Rule{{
 			NameScope: ".",
 			Format:    CommonLogFormat,
-			Class:     map[response.Class]bool{response.Denial: true, response.Error: true},
+			Class:     map[response.Class]struct{}{response.Denial: struct{}{}, response.Error: struct{}{}},
 		}}},
 		{`log {
 			class abracadabra
diff --git a/plugin/metrics/metrics.go b/plugin/metrics/metrics.go
index 159eec014..2a87dcb17 100644
--- a/plugin/metrics/metrics.go
+++ b/plugin/metrics/metrics.go
@@ -26,7 +26,7 @@ type Metrics struct {
 	srv     *http.Server
 
 	zoneNames []string
-	zoneMap   map[string]bool
+	zoneMap   map[string]struct{}
 	zoneMu    sync.RWMutex
 }
 
@@ -35,7 +35,7 @@ func New(addr string) *Metrics {
 	met := &Metrics{
 		Addr:    addr,
 		Reg:     prometheus.NewRegistry(),
-		zoneMap: make(map[string]bool),
+		zoneMap: make(map[string]struct{}),
 	}
 	// Add the default collectors
 	met.MustRegister(prometheus.NewGoCollector())
@@ -69,7 +69,7 @@ func (m *Metrics) MustRegister(c prometheus.Collector) {
 // AddZone adds zone z to m.
 func (m *Metrics) AddZone(z string) {
 	m.zoneMu.Lock()
-	m.zoneMap[z] = true
+	m.zoneMap[z] = struct{}{}
 	m.zoneNames = keys(m.zoneMap)
 	m.zoneMu.Unlock()
 }
@@ -140,7 +140,7 @@ func (m *Metrics) OnFinalShutdown() error {
 	return m.stopServer()
 }
 
-func keys(m map[string]bool) []string {
+func keys(m map[string]struct{}) []string {
 	sx := []string{}
 	for k := range m {
 		sx = append(sx, k)
diff --git a/plugin/metrics/vars/report.go b/plugin/metrics/vars/report.go
index d0c64b864..f354b6551 100644
--- a/plugin/metrics/vars/report.go
+++ b/plugin/metrics/vars/report.go
@@ -50,25 +50,25 @@ func WithServer(ctx context.Context) string {
 	return srv.(string)
 }
 
-var monitorType = map[uint16]bool{
-	dns.TypeAAAA:   true,
-	dns.TypeA:      true,
-	dns.TypeCNAME:  true,
-	dns.TypeDNSKEY: true,
-	dns.TypeDS:     true,
-	dns.TypeMX:     true,
-	dns.TypeNSEC3:  true,
-	dns.TypeNSEC:   true,
-	dns.TypeNS:     true,
-	dns.TypePTR:    true,
-	dns.TypeRRSIG:  true,
-	dns.TypeSOA:    true,
-	dns.TypeSRV:    true,
-	dns.TypeTXT:    true,
+var monitorType = map[uint16]struct{}{
+	dns.TypeAAAA:   struct{}{},
+	dns.TypeA:      struct{}{},
+	dns.TypeCNAME:  struct{}{},
+	dns.TypeDNSKEY: struct{}{},
+	dns.TypeDS:     struct{}{},
+	dns.TypeMX:     struct{}{},
+	dns.TypeNSEC3:  struct{}{},
+	dns.TypeNSEC:   struct{}{},
+	dns.TypeNS:     struct{}{},
+	dns.TypePTR:    struct{}{},
+	dns.TypeRRSIG:  struct{}{},
+	dns.TypeSOA:    struct{}{},
+	dns.TypeSRV:    struct{}{},
+	dns.TypeTXT:    struct{}{},
 	// Meta Qtypes
-	dns.TypeIXFR: true,
-	dns.TypeAXFR: true,
-	dns.TypeANY:  true,
+	dns.TypeIXFR: struct{}{},
+	dns.TypeAXFR: struct{}{},
+	dns.TypeANY:  struct{}{},
 }
 
 const other = "other"