From 64e45ab19997ef0b543095835bcde613f5153f0f Mon Sep 17 00:00:00 2001
From: Thibaud DESODT <thibaud.desodt@dgtresor.gouv.fr>
Date: Tue, 7 Nov 2017 07:16:48 +0100
Subject: [PATCH] Make ReadFrom.KeyValuePairs not throw when duplicate keys

Instead, take the last value of each key, to remove work from future Serilog.Settings.Combined
---
 .../LoggerSettingsConfiguration.cs            | 12 ++++++++-
 .../Settings/KeyValuePairSettingsTests.cs     | 25 +++++++++++--------
 2 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/src/Serilog/Configuration/LoggerSettingsConfiguration.cs b/src/Serilog/Configuration/LoggerSettingsConfiguration.cs
index ce279f0eb..6acbf70ac 100644
--- a/src/Serilog/Configuration/LoggerSettingsConfiguration.cs
+++ b/src/Serilog/Configuration/LoggerSettingsConfiguration.cs
@@ -50,11 +50,21 @@ public LoggerConfiguration Settings(ILoggerSettings settings)
         /// </summary>
         /// <param name="settings">A list of key-value pairs describing logger settings.</param>
         /// <returns>Configuration object allowing method chaining.</returns>
+        /// <remarks>In case of duplicate keys, the last value for the key is kept and the previous ones are ignored.</remarks>
         public LoggerConfiguration KeyValuePairs(IEnumerable<KeyValuePair<string, string>> settings)
         {
             if (settings == null) throw new ArgumentNullException(nameof(settings));
+            var uniqueSettings = new Dictionary<string, string>();
+            foreach (var kvp in settings)
+            {
+                uniqueSettings[kvp.Key] = kvp.Value;
+            }
+            return KeyValuePairs(uniqueSettings);
+        }
 
-            return Settings(new KeyValuePairSettings(settings.ToDictionary(x => x.Key, x => x.Value)));
+        LoggerConfiguration KeyValuePairs(IReadOnlyDictionary<string, string> settings)
+        {
+            return Settings(new KeyValuePairSettings(settings));
         }
     }
 }
diff --git a/test/Serilog.Tests/Settings/KeyValuePairSettingsTests.cs b/test/Serilog.Tests/Settings/KeyValuePairSettingsTests.cs
index d20f57889..275f82b82 100644
--- a/test/Serilog.Tests/Settings/KeyValuePairSettingsTests.cs
+++ b/test/Serilog.Tests/Settings/KeyValuePairSettingsTests.cs
@@ -16,19 +16,24 @@ namespace Serilog.Tests.Settings
     public class KeyValuePairSettingsTests
     {
         [Fact]
-        public void DuplicateKeysCauseArgumentException()
+        public void LastValueIsTakenWhenKeysAreDuplicate()
         {
-            Action action = () => new LoggerConfiguration()
+            LogEvent evt = null;
+            var log = new LoggerConfiguration()
                 .ReadFrom.KeyValuePairs(new List<KeyValuePair<string, string>>
                 {
-                    new KeyValuePair<string, string>("setting", "Value"),
-                    new KeyValuePair<string, string>("setting", "SameSettingOtherValue"),
-                });
+                    new KeyValuePair<string, string>("enrich:with-property:App", "InitialValue"),
+                    new KeyValuePair<string, string>("enrich:with-property:App", "OverridenValue"),
+                    new KeyValuePair<string, string>("enrich:with-property:App", "FinalValue")
+                })
+                .WriteTo.Sink(new DelegatingSink(e => evt = e))
+                .CreateLogger();
 
-            var ex = Assert.ThrowsAny<ArgumentException>(action);
-            Assert.NotNull(ex);
-            Assert.Contains("An item with the same key has already been added.", ex.Message);
-        }        
+            log.Information("Has a test property");
+
+            Assert.NotNull(evt);
+            Assert.Equal("FinalValue", evt.Properties["App"].LiteralValue());
+        }
 
         [Fact]
         public void FindsConfigurationAssemblies()
@@ -328,7 +333,7 @@ public void LoggingLevelSwitchCanBeUsedForMinimumLevelOverrides()
             systemLogger.Write(Some.WarningEvent());
             Assert.False(evt is null, "LoggingLevelSwitch initial level was Warning for logger System.*. It should log Warning messages for SourceContext System.Bar");
 
-            
+
             evt = null;
             var controlSwitch = DummyWithLevelSwitchSink.ControlLevelSwitch;