added detection for duplicate names in yaml sequence

src/Persistence.Tests/PaYaml/Serialization/PaYamlSerializerTests.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+using Microsoft.PowerPlatform.PowerApps.Persistence;
+using Microsoft.PowerPlatform.PowerApps.Persistence.PaYaml.Models;
 using Microsoft.PowerPlatform.PowerApps.Persistence.PaYaml.Models.SchemaV3;
 using Microsoft.PowerPlatform.PowerApps.Persistence.PaYaml.Serialization;
 
@@ -152,6 +154,14 @@ public void DeserializeExamplePaYamlSingleFileApp()
             .And.ContainNames("Label1", "TextInput1");
     }
 
+    [TestMethod]
+    public void DeserializeDuplicateControlNamesShouldFail()
+    {
+        var path = @"_TestData/InvalidYaml-CI/duplicate-control-in-sequence.pa.yaml";
+        var ex = Assert.ThrowsException<PersistenceLibraryException>(() => PaYamlSerializer.Deserialize<NamedObjectSequence<ControlInstance>>(File.ReadAllText(path)));
+        ex.ErrorCode.Should().Be(PersistenceErrorCode.DuplicateNameInSequence);
+    }
+
     #endregion
 
     #region RoundTrip from yaml

src/Persistence.Tests/_TestData/InvalidYaml-CI/duplicate-control-in-sequence.pa.yaml

@@ -0,0 +1,10 @@
+- Label1:
+    Control: Label
+    Properties:
+      X: =40
+      Y: =40
+- Label1:
+    Control: Label
+    Properties:
+      X: =60
+      Y: =60

src/Persistence/PaYaml/Serialization/PaYamlSerializer.cs

@@ -117,7 +117,11 @@ private static void WriteTextWriter<TValue>(TextWriter writer, in TValue? value,
         }
         catch (YamlException ex)
         {
-            throw PersistenceLibraryException.FromYamlException(ex, PersistenceErrorCode.YamlInvalidSyntax);
+            var errorCode = PersistenceErrorCode.YamlInvalidSyntax;
+            if (ex.InnerException is ArgumentException && ex.InnerException.Message.Contains("An item with the same key has already been added"))
+                errorCode = PersistenceErrorCode.DuplicateNameInSequence;
+
+            throw PersistenceLibraryException.FromYamlException(ex, errorCode);
         }
 
         // TODO: Consider using FluentValidation nuget package to validate the deserialized object

src/Persistence/PersistenceErrorCode.cs

@@ -26,6 +26,7 @@ public enum PersistenceErrorCode
     InvalidEditorStateJson = 3300,
     ControlInstanceInvalid = 3501,
     RoundTripValidationFailed = 3502,
+    DuplicateNameInSequence = 3503,
 
     //
     MsappArchiveError = 5000,
@@ -64,6 +65,7 @@ internal static PersistenceErrorCode CheckArgumentInRange(this PersistenceErrorC
             PersistenceErrorCode.InvalidEditorStateJson => "An editor state json file could not be deserialized due to being invalid.",
             PersistenceErrorCode.ControlInstanceInvalid => "A control instance object in YAML has an invalid state.",
             PersistenceErrorCode.RoundTripValidationFailed => "Round trip yaml validation failed.",
+            PersistenceErrorCode.DuplicateNameInSequence => "An item name was duplicated.",
             PersistenceErrorCode.MsappArchiveError => "An error was detected in an msapp file.",
             PersistenceErrorCode._LastErrorExclusive => throw new InvalidOperationException("The error code is out of range."),
             _ => "An exception occurred in the persistence library.",