Prevent duplicate entries in User Agent custom components

Author: muhammad-othman

generator/.DevConfigs/e890aefd-0815-4204-a9bb-e1b5754184a3.json

@@ -0,0 +1,9 @@
+{
+  "core": {
+    "changeLogMessages": [
+      "Prevent duplicate entries in User Agent custom components"
+    ],
+    "type": "patch",
+    "updateMinimum": true
+  }
+}

sdk/src/Core/Amazon.Runtime/Internal/UserAgent/UserAgentDetails.cs

@@ -27,7 +27,7 @@ public class UserAgentDetails
     {
         private const int MaxSizeBytes = 1024; // 1 KB size limit
         private readonly HashSet<string> _trackedFeatureIds = new HashSet<string>();
-        private readonly StringBuilder _userAgentBuilder = new StringBuilder();
+        private readonly HashSet<string> _userAgentCustomComponents = new HashSet<string>();
 
         /// <summary>
         /// Gets the list of tracked feature IDs.
@@ -40,9 +40,9 @@ public class UserAgentDetails
         /// <param name="component">The user-agent component to append.</param>
         public void AddUserAgentComponent(string component)
         {
-            if (!string.IsNullOrEmpty(component))
+            if (!string.IsNullOrWhiteSpace(component))
             {
-                _userAgentBuilder.Append(' ').Append(component);
+                _userAgentCustomComponents.Add(component.Trim());
             }
         }
 
@@ -62,7 +62,7 @@ public void AddFeature(UserAgentFeatureId featureId)
         /// </summary>
         public string GetCustomUserAgentComponents()
         {
-            return _userAgentBuilder.ToString().Trim();
+            return string.Join(" ", _userAgentCustomComponents);
         }
 
         /// <summary>
@@ -74,9 +74,9 @@ public string GenerateUserAgentWithMetrics()
             var metricsUserAgent = GenerateMetricsUserAgent();
             if (!string.IsNullOrEmpty(metricsUserAgent))
             {
-                return $"{_userAgentBuilder.ToString().Trim()} {metricsUserAgent}";
+                return $"{string.Join(" ", _userAgentCustomComponents)} {metricsUserAgent}";
             }
-            return _userAgentBuilder.ToString().Trim();
+            return string.Join(" ", _userAgentCustomComponents);
         }
 
         /// <summary>

sdk/test/UnitTests/Custom/Runtime/UserAgentTests.cs

@@ -232,6 +232,43 @@ public void Test_AddsCustomUserAgentAddition()
             Assert.IsTrue(userAgentParts.Contains(userAgentAddition));
         }
 
+        [TestMethod]
+        public void Test_AddsCustomUserAgentAddition_SkipDuplicates()
+        {
+            var userAgentAddition = "custom-feature/1.0";
+            var userAgentAddition2 = "custom-feature/2.0";
+
+            var putObjectRequest = new PutObjectRequest
+            {
+                BucketName = "test-bucket",
+                Key = "test-key",
+                ContentBody = "test-content",
+            };
+
+            var userAgentDetails = ((IAmazonWebServiceRequest)putObjectRequest).UserAgentDetails;
+
+            userAgentDetails.AddUserAgentComponent(userAgentAddition);
+            userAgentDetails.AddUserAgentComponent(userAgentAddition);
+
+            userAgentDetails.AddUserAgentComponent(userAgentAddition2);
+            userAgentDetails.AddUserAgentComponent(userAgentAddition2);
+            userAgentDetails.AddUserAgentComponent(userAgentAddition2);
+
+            var config = new AmazonS3Config();
+            var request = RunMockRequest(putObjectRequest, config, new PutObjectRequestMarshaller(), new PutObjectResponseUnmarshaller());
+
+            request.Headers.TryGetValue(HeaderKeys.UserAgentHeader, out string userAgentHeader);
+            Assert.IsNotNull(userAgentHeader);
+
+            var userAgentParts = userAgentHeader.Split(' ');
+
+            Assert.IsTrue(userAgentParts.Contains(userAgentAddition));
+            Assert.AreEqual(1, userAgentParts.Count(e => e == userAgentAddition));
+
+            Assert.IsTrue(userAgentParts.Contains(userAgentAddition2));
+            Assert.AreEqual(1, userAgentParts.Count(e => e == userAgentAddition2));
+        }
+
         [TestMethod]
         public void ObservabilityFeatureIds_NoInUserAgentByDefault()
         {