NLogLoggingConfiguration - Add support for config variables with JsonLayout (#465)

Author: snakefoot

src/NLog.Extensions.Logging/Config/NLogLoggingConfiguration.cs

@@ -160,15 +160,6 @@ public LoggingConfigurationElement(IConfigurationSection configurationSection, s
 
             private IEnumerable<KeyValuePair<string, string>> GetValues()
             {
-                var children = _configurationSection.GetChildren();
-                foreach (var child in children)
-                {
-                    if (!child.GetChildren().Any())
-                    {
-                        yield return new KeyValuePair<string, string>(GetConfigKey(child), child.Value);
-                    }
-                }
-
                 if (_nameOverride != null)
                 {
                     if (ReferenceEquals(_nameOverride, DefaultTargetParameters))
@@ -182,7 +173,20 @@ private IEnumerable<KeyValuePair<string, string>> GetValues()
 
                     if (ReferenceEquals(_nameOverride, VariableKey))
                     {
-                        yield return new KeyValuePair<string, string>("value", _configurationSection.Value);
+                        var value = _configurationSection.Value;
+                        if (value != null)
+                            yield return new KeyValuePair<string, string>("value", value);
+                        else
+                            yield break;    // Signal to NLog Config Parser to check GetChildren() for variable layout
+                    }
+                }
+
+                var children = _configurationSection.GetChildren();
+                foreach (var child in children)
+                {
+                    if (!child.GetChildren().Any())
+                    {
+                        yield return new KeyValuePair<string, string>(GetConfigKey(child), child.Value);
                     }
                 }
             }
@@ -207,10 +211,17 @@ private IEnumerable<ILoggingConfigurationElement> GetChildren()
                     }
                 }
 
-                var children = _configurationSection.GetChildren();
-                foreach (var loggingConfigurationElement in GetChildren(children, variables, isTargetsSection))
+                if (ReferenceEquals(_nameOverride, VariableKey) && _configurationSection.Value == null)
+                {
+                    yield return new LoggingConfigurationElement(_configurationSection);
+                }
+                else
                 {
-                    yield return loggingConfigurationElement;
+                    var children = _configurationSection.GetChildren();
+                    foreach (var loggingConfigurationElement in GetChildren(children, variables, isTargetsSection))
+                    {
+                        yield return loggingConfigurationElement;
+                    }
                 }
             }
 

test/NLog.Extensions.Logging.Tests/NLogLoggingConfigurationTests.cs

@@ -102,6 +102,31 @@ public void LoadVariablesConfig()
             Assert.Equal("hello.txt", (logConfig.FindTargetByName("file") as FileTarget)?.FileName.Render(LogEventInfo.CreateNullEvent()));
         }
 
+        [Fact]
+        public void LoadVariableJsonLayoutConfig()
+        {
+            var memoryConfig = CreateMemoryConfigConsoleTargetAndRule();
+            memoryConfig["NLog:Targets:file:type"] = "File";
+            memoryConfig["NLog:Targets:file:fileName"] = "hello.txt";
+            memoryConfig["NLog:Targets:file:layout"] = "${my_json}";
+            memoryConfig["NLog:Targets:console:layout"] = "${my_json}";
+            memoryConfig["NLog:Variables:my_json:type"] = "JsonLayout";
+            memoryConfig["NLog:Variables:my_json:attributes:0:name"] = "message";
+            memoryConfig["NLog:Variables:my_json:attributes:0:layout"] = "${message}";
+            memoryConfig["NLog:Variables:my_json:attributes:1:name"] = "logger";
+            memoryConfig["NLog:Variables:my_json:attributes:1:layout"] = "${logger}";
+
+            var logConfig = CreateNLogLoggingConfigurationWithNLogSection(memoryConfig);
+
+            Assert.Single(logConfig.LoggingRules);
+            Assert.Equal(1, logConfig.Variables.Count);
+            Assert.Equal(2, logConfig.LoggingRules[0].Targets.Count);
+            Assert.Equal(2, logConfig.AllTargets.Count);
+            Assert.Single(logConfig.AllTargets.Where(t => t is FileTarget));
+            Assert.Single(logConfig.AllTargets.Where(t => t is ConsoleTarget));
+            Assert.Equal(2, logConfig.AllTargets.Count(t => (t as TargetWithLayout)?.Layout is NLog.Layouts.JsonLayout));
+        }
+
         [Fact]
         public void LoadDefaultWrapperConfig()
         {