Enable debug globally if enabled in any server config (#4007)

* Enable debug globally if enabled in any server config

It was currently enabled only if the plugin debug
was enabled in the last server config of the Corefile.

Signed-off-by: Olivier Lemasle <o.lemasle@gmail.com>

* Add test and update debug's README

Signed-off-by: Olivier Lemasle <o.lemasle@gmail.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/core/dnsserver/server_test.go b/core/dnsserver/server_test.go
index c3bed02bc..d7289474b 100644
--- a/core/dnsserver/server_test.go
+++ b/core/dnsserver/server_test.go
@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"github.com/coredns/coredns/plugin"
+	"github.com/coredns/coredns/plugin/pkg/log"
 	"github.com/coredns/coredns/plugin/test"
 
 	"github.com/miekg/dns"
@@ -48,6 +49,33 @@ func TestNewServer(t *testing.T) {
 	}
 }
 
+func TestDebug(t *testing.T) {
+	configNoDebug, configDebug := testConfig("dns", testPlugin{}), testConfig("dns", testPlugin{})
+	configDebug.Debug = true
+
+	s1, err := NewServer("127.0.0.1:53", []*Config{configDebug, configNoDebug})
+	if err != nil {
+		t.Errorf("Expected no error for NewServer, got %s", err)
+	}
+	if !s1.debug {
+		t.Errorf("Expected debug mode enabled for server s1")
+	}
+	if !log.D.Value() {
+		t.Errorf("Expected debug logging enabled")
+	}
+
+	s2, err := NewServer("127.0.0.1:53", []*Config{configNoDebug})
+	if err != nil {
+		t.Errorf("Expected no error for NewServer, got %s", err)
+	}
+	if s2.debug {
+		t.Errorf("Expected debug mode disabled for server s2")
+	}
+	if log.D.Value() {
+		t.Errorf("Expected debug logging disabled")
+	}
+}
+
 func BenchmarkCoreServeDNS(b *testing.B) {
 	s, err := NewServer("127.0.0.1:53", []*Config{testConfig("dns", testPlugin{})})
 	if err != nil {