Fix PendingModelChangesWarning for Unicode diacritics (NFC/NFD) on Linux

src/EFCore/ChangeTracking/ValueComparer.cs

@@ -304,10 +304,14 @@ public static ValueComparer CreateDefault
             return new DefaultDateTimeOffsetValueComparer(favorStructuralComparisons);
         }
 
+        if (nonNullableType == typeof(string))
+        {
+            return new DefaultStringValueComparer(favorStructuralComparisons);
+        }
+
         return nonNullableType.IsInteger()
             || nonNullableType == typeof(decimal)
             || nonNullableType == typeof(bool)
-            || nonNullableType == typeof(string)
             || nonNullableType == typeof(DateTime)
             || nonNullableType == typeof(DateOnly)
             || nonNullableType == typeof(Guid)
@@ -376,4 +380,23 @@ private static readonly MethodInfo EqualsExactMethodInfo
         public override Expression ExtractEqualsBody(Expression leftExpression, Expression rightExpression)
             => Expression.Call(leftExpression, EqualsExactMethodInfo, rightExpression);
     }
+
+#pragma warning disable CA1309 // Use ordinal StringComparison - InvariantCulture is intentional to handle Unicode canonical equivalence (NFC/NFD)
+    internal sealed class DefaultStringValueComparer(bool favorStructuralComparisons)
+        : DefaultValueComparer<string>((v1, v2) => string.Equals(v1, v2, StringComparison.InvariantCulture), favorStructuralComparisons)
+    {
+        private static readonly MethodInfo StringEqualsMethodInfo
+            = typeof(string).GetMethod(nameof(string.Equals), [typeof(string), typeof(string), typeof(StringComparison)])!;
+
+        // String canonical equivalence (e.g. NFC vs NFD Unicode normalization) is handled by InvariantCulture comparison.
+        // Override hash code to be consistent with InvariantCulture equality so that canonically equivalent strings
+        // produce the same hash code.
+        public override int GetHashCode(string instance)
+            => StringComparer.InvariantCulture.GetHashCode(instance);
+
+        public override Expression ExtractEqualsBody(Expression leftExpression, Expression rightExpression)
+            => Expression.Call(StringEqualsMethodInfo, leftExpression, rightExpression, Expression.Constant(StringComparison.InvariantCulture));
+    }
+#pragma warning restore CA1309
 }
+

src/EFCore/ChangeTracking/ValueComparerExtensions.cs

@@ -17,6 +17,19 @@ public static class ValueComparerExtensions
     /// <param name="valueComparer">The value comparer.</param>
     /// <returns><see langword="true" /> if the value comparer is the default; <see langword="false" /> otherwise.</returns>
     public static bool IsDefault(this ValueComparer valueComparer)
-        => valueComparer.GetType().IsGenericType
-            && valueComparer.GetType().GetGenericTypeDefinition() == typeof(ValueComparer.DefaultValueComparer<>);
+    {
+        var type = valueComparer.GetType();
+        while (type != null && type != typeof(object))
+        {
+            if (type.IsGenericType
+                && type.GetGenericTypeDefinition() == typeof(ValueComparer.DefaultValueComparer<>))
+            {
+                return true;
+            }
+
+            type = type.BaseType;
+        }
+
+        return false;
+    }
 }

test/EFCore.Cosmos.FunctionalTests/Scaffolding/Baselines/Basic_cosmos_model/DataEntityType.cs

@@ -94,7 +94,7 @@ public static RuntimeEntityType Create(RuntimeModel model, RuntimeEntityType bas
                     int (long v) => ((object)v).GetHashCode(),
                     long (long v) => v),
                 providerValueComparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 converter: new ValueConverter<long, string>(
@@ -151,7 +151,7 @@ public static RuntimeEntityType Create(RuntimeModel model, RuntimeEntityType bas
                     int (byte[] v) => StructuralComparisons.StructuralEqualityComparer.GetHashCode(((object)v)),
                     byte[] (byte[] source) => source.ToArray()),
                 providerValueComparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 converter: new ValueConverter<byte[], string>(
@@ -271,7 +271,7 @@ public static RuntimeEntityType Create(RuntimeModel model, RuntimeEntityType bas
                 storeGenerationIndex: -1);
             map.TypeMapping = CosmosTypeMapping.Default.Clone(
                 comparer: new StringDictionaryComparer<Dictionary<string, string[]>, string[]>(new ConvertingValueComparer<string[], object>(new ListOfReferenceTypesComparer<string[], string>(new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v)))),
                 keyComparer: new ValueComparer<Dictionary<string, string[]>>(
@@ -305,15 +305,15 @@ public static RuntimeEntityType Create(RuntimeModel model, RuntimeEntityType bas
                 storeGenerationIndex: -1);
             __id.TypeMapping = CosmosTypeMapping.Default.Clone(
                 comparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 keyComparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 providerValueComparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 clrType: typeof(string),
@@ -375,15 +375,15 @@ public static RuntimeEntityType Create(RuntimeModel model, RuntimeEntityType bas
                 storeGenerationIndex: 1);
             _etag.TypeMapping = CosmosTypeMapping.Default.Clone(
                 comparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 keyComparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 providerValueComparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 clrType: typeof(string),

test/EFCore.Cosmos.FunctionalTests/Scaffolding/Baselines/BigModel/DependentBaseEntityType.cs

@@ -96,7 +96,7 @@ public static RuntimeEntityType Create(RuntimeModel model, RuntimeEntityType bas
                     int (Guid v) => ((object)v).GetHashCode(),
                     Guid (Guid v) => v),
                 providerValueComparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 converter: new ValueConverter<Guid, string>(
@@ -217,15 +217,15 @@ public static RuntimeEntityType Create(RuntimeModel model, RuntimeEntityType bas
                 storeGenerationIndex: -1);
             __id.TypeMapping = CosmosTypeMapping.Default.Clone(
                 comparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 keyComparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 providerValueComparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 clrType: typeof(string),

test/EFCore.Cosmos.FunctionalTests/Scaffolding/Baselines/BigModel/DependentDerivedEntityType.cs

@@ -66,15 +66,15 @@ public static RuntimeEntityType Create(RuntimeModel model, RuntimeEntityType bas
                 storeGenerationIndex: -1);
             data.TypeMapping = CosmosTypeMapping.Default.Clone(
                 comparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 keyComparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 providerValueComparer: new ValueComparer<string>(
-                    bool (string v1, string v2) => v1 == v2,
+                    bool (string v1, string v2) => string.Equals(v1, v2, StringComparison.InvariantCulture),
                     int (string v) => ((object)v).GetHashCode(),
                     string (string v) => v),
                 clrType: typeof(string),