Cosmos: return null instead of throwing from Find

src/EFCore.Cosmos/Query/Internal/CosmosQueryableMethodTranslatingExpressionVisitor.cs

@@ -129,7 +129,7 @@ public override Expression Visit(Expression expression)
                                     var readItemExpression = new ReadItemExpression(entityType, propertyParameterList);
 
                                     return CreateShapedQueryExpression(entityType, readItemExpression)
-                                        .UpdateResultCardinality(ResultCardinality.Single);
+                                        .UpdateResultCardinality(ResultCardinality.SingleOrDefault);
                                 }
                             }
                         }

src/EFCore.Cosmos/Storage/Internal/CosmosClientWrapper.cs

@@ -551,7 +551,7 @@ public virtual IAsyncEnumerable<JObject> ExecuteSqlQueryAsync(
         ///     any release. You should only use it directly in your code with extreme caution and knowing that
         ///     doing so can result in application failures when updating to a new Entity Framework Core release.
         /// </summary>
-        public virtual JObject ExecuteReadItem(
+        public virtual JObject? ExecuteReadItem(
             string containerId,
             string? partitionKey,
             string resourceId)
@@ -577,7 +577,7 @@ public virtual JObject ExecuteReadItem(
         ///     any release. You should only use it directly in your code with extreme caution and knowing that
         ///     doing so can result in application failures when updating to a new Entity Framework Core release.
         /// </summary>
-        public virtual async Task<JObject> ExecuteReadItemAsync(
+        public virtual async Task<JObject?> ExecuteReadItemAsync(
             string containerId,
             string? partitionKey,
             string resourceId,
@@ -622,8 +622,13 @@ private static Task<ResponseMessage> CreateSingleItemQueryAsync(
                     cancellationToken: cancellationToken);
         }
 
-        private static JObject JObjectFromReadItemResponseMessage(ResponseMessage responseMessage)
+        private static JObject? JObjectFromReadItemResponseMessage(ResponseMessage responseMessage)
         {
+            if (responseMessage.StatusCode == HttpStatusCode.NotFound)
+            {
+                return null;
+            }
+
             responseMessage.EnsureSuccessStatusCode();
 
             var responseStream = responseMessage.Content;

src/EFCore.Cosmos/Storage/Internal/ICosmosClientWrapper.cs

@@ -148,7 +148,7 @@ Task<bool> DeleteItemAsync(
         ///     any release. You should only use it directly in your code with extreme caution and knowing that
         ///     doing so can result in application failures when updating to a new Entity Framework Core release.
         /// </summary>
-        JObject ExecuteReadItem(
+        JObject? ExecuteReadItem(
             string containerId,
             string? partitionKey,
             string resourceId);
@@ -159,7 +159,7 @@ JObject ExecuteReadItem(
         ///     any release. You should only use it directly in your code with extreme caution and knowing that
         ///     doing so can result in application failures when updating to a new Entity Framework Core release.
         /// </summary>
-        Task<JObject> ExecuteReadItemAsync(
+        Task<JObject?> ExecuteReadItemAsync(
             string containerId,
             string? partitionKey,
             string resourceId,

test/EFCore.Cosmos.FunctionalTests/FindCosmosTest.cs

@@ -0,0 +1,83 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Threading.Tasks;
+using Microsoft.EntityFrameworkCore.TestUtilities;
+using Xunit;
+
+namespace Microsoft.EntityFrameworkCore
+{
+    public abstract class FindCosmosTest : FindTestBase<FindCosmosTest.FindCosmosFixture>
+    {
+        protected FindCosmosTest(FindCosmosFixture fixture)
+            : base(fixture)
+        {
+            fixture.TestSqlLoggerFactory.Clear();
+        }
+
+        [ConditionalFact(Skip = "#25886")]
+        public override void Find_base_type_using_derived_set_tracked() {}
+
+        [ConditionalFact(Skip = "#25886")]
+        public override Task Find_base_type_using_derived_set_tracked_async()
+            => Task.CompletedTask;
+
+        [ConditionalFact(Skip = "#25886")]
+        public override void Find_derived_using_base_set_type_from_store() {}
+
+        [ConditionalFact(Skip = "#25886")]
+        public override Task Find_derived_using_base_set_type_from_store_async()
+            => Task.CompletedTask;
+
+        public class FindCosmosTestSet : FindCosmosTest
+        {
+            public FindCosmosTestSet(FindCosmosFixture fixture)
+                : base(fixture)
+            {
+            }
+
+            protected override TEntity Find<TEntity>(DbContext context, params object[] keyValues)
+                => context.Set<TEntity>().Find(keyValues);
+
+            protected override ValueTask<TEntity> FindAsync<TEntity>(DbContext context, params object[] keyValues)
+                => context.Set<TEntity>().FindAsync(keyValues);
+        }
+
+        public class FindCosmosTestContext : FindCosmosTest
+        {
+            public FindCosmosTestContext(FindCosmosFixture fixture)
+                : base(fixture)
+            {
+            }
+
+            protected override TEntity Find<TEntity>(DbContext context, params object[] keyValues)
+                => context.Find<TEntity>(keyValues);
+
+            protected override ValueTask<TEntity> FindAsync<TEntity>(DbContext context, params object[] keyValues)
+                => context.FindAsync<TEntity>(keyValues);
+        }
+
+        public class FindCosmosTestNonGeneric : FindCosmosTest
+        {
+            public FindCosmosTestNonGeneric(FindCosmosFixture fixture)
+                : base(fixture)
+            {
+            }
+
+            protected override TEntity Find<TEntity>(DbContext context, params object[] keyValues)
+                => (TEntity)context.Find(typeof(TEntity), keyValues);
+
+            protected override async ValueTask<TEntity> FindAsync<TEntity>(DbContext context, params object[] keyValues)
+                => (TEntity)await context.FindAsync(typeof(TEntity), keyValues);
+        }
+
+        public class FindCosmosFixture : FindFixtureBase
+        {
+            public TestSqlLoggerFactory TestSqlLoggerFactory
+                => (TestSqlLoggerFactory)ListLoggerFactory;
+
+            protected override ITestStoreFactory TestStoreFactory
+                => CosmosTestStoreFactory.Instance;
+        }
+    }
+}