Fix ExecuteUpdate over scalar projections (#37791)

Fixes #37771

Author: roji

src/EFCore/Query/Internal/NavigationExpandingExpressionVisitor.cs

@@ -61,6 +61,9 @@ private static readonly PropertyInfo QueryContextContextPropertyInfo
     private static readonly bool UseOldBehavior37247 =
         AppContext.TryGetSwitch("Microsoft.EntityFrameworkCore.Issue37247", out var enabled) && enabled;
 
+    private static readonly bool UseOldBehavior37771 =
+        AppContext.TryGetSwitch("Microsoft.EntityFrameworkCore.Issue37771", out var enabled) && enabled;
+
     /// <summary>
     ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
     ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
@@ -1071,11 +1074,18 @@ private Expression ProcessExecuteUpdate(NavigationExpansionExpression source, Me
         {
             // Apply any pending selector before processing the ExecuteUpdate setters; this adds a Select() (if necessary) before
             // ExecuteUpdate, to avoid the pending selector flowing into each setter lambda and making it more complicated.
+            // However, only do this when the pending selector produces entity/structural type references (i.e. the snapshot is not just
+            // a DefaultExpression). When the pending selector projects only scalar values (e.g. select new { p.Used, n.Qty }),
+            // applying it would lose the connection between the projected scalar and the original entity property, breaking
+            // ExecuteUpdate's property selector recognition (#37771).
             var newStructure = SnapshotExpression(source.PendingSelector);
-            var queryable = Reduce(source);
-            var navigationTree = new NavigationTreeExpression(newStructure);
-            var parameterName = source.CurrentParameter.Name ?? GetParameterName("e");
-            source = new NavigationExpansionExpression(queryable, navigationTree, navigationTree, parameterName);
+            if (newStructure is not DefaultExpression || UseOldBehavior37771)
+            {
+                var queryable = Reduce(source);
+                var navigationTree = new NavigationTreeExpression(newStructure);
+                var parameterName = source.CurrentParameter.Name ?? GetParameterName("e");
+                source = new NavigationExpansionExpression(queryable, navigationTree, navigationTree, parameterName);
+            }
         }
 
         NewArrayExpression settersArray;

test/EFCore.Relational.Specification.Tests/BulkUpdates/NorthwindBulkUpdatesRelationalTestBase.cs

@@ -99,6 +99,44 @@ FROM [Customers]
                 }
             });
 
+    [ConditionalTheory, MemberData(nameof(IsAsyncData))] // #37771
+    public virtual Task Update_with_select_mixed_entity_scalar_anonymous_projection(bool async)
+        => TestHelpers.ExecuteWithStrategyInTransactionAsync(
+            () => Fixture.CreateContext(),
+            (facade, transaction) => Fixture.UseTransaction(facade, transaction),
+            async context =>
+            {
+                var queryable = context.Set<Customer>().Select(c => new { Entity = c, c.ContactName });
+
+                if (async)
+                {
+                    await queryable.ExecuteUpdateAsync(s => s.SetProperty(c => c.Entity.ContactName, "Updated"));
+                }
+                else
+                {
+                    queryable.ExecuteUpdate(s => s.SetProperty(c => c.Entity.ContactName, "Updated"));
+                }
+            });
+
+    [ConditionalTheory, MemberData(nameof(IsAsyncData))] // #37771
+    public virtual Task Update_with_select_scalar_anonymous_projection(bool async)
+        => TestHelpers.ExecuteWithStrategyInTransactionAsync(
+            () => Fixture.CreateContext(),
+            (facade, transaction) => Fixture.UseTransaction(facade, transaction),
+            async context =>
+            {
+                var queryable = context.Set<Customer>().Select(c => new { c.ContactName, c.City });
+
+                if (async)
+                {
+                    await queryable.ExecuteUpdateAsync(s => s.SetProperty(c => c.ContactName, "Updated"));
+                }
+                else
+                {
+                    queryable.ExecuteUpdate(s => s.SetProperty(c => c.ContactName, "Updated"));
+                }
+            });
+
     protected static async Task AssertTranslationFailed(string details, Func<Task> query)
         => Assert.Contains(
             CoreStrings.NonQueryTranslationFailedWithDetails("", details)[21..],

test/EFCore.SqlServer.FunctionalTests/BulkUpdates/NorthwindBulkUpdatesSqlServerTest.cs

@@ -1651,6 +1651,34 @@ OFFSET @p ROWS
 """);
     }
 
+    public override async Task Update_with_select_mixed_entity_scalar_anonymous_projection(bool async)
+    {
+        await base.Update_with_select_mixed_entity_scalar_anonymous_projection(async);
+
+        AssertSql(
+            """
+@p='Updated' (Size = 30)
+
+UPDATE [c]
+SET [c].[ContactName] = @p
+FROM [Customers] AS [c]
+""");
+    }
+
+    public override async Task Update_with_select_scalar_anonymous_projection(bool async)
+    {
+        await base.Update_with_select_scalar_anonymous_projection(async);
+
+        AssertSql(
+            """
+@p='Updated' (Size = 30)
+
+UPDATE [c]
+SET [c].[ContactName] = @p
+FROM [Customers] AS [c]
+""");
+    }
+
     private void AssertSql(params string[] expected)
         => Fixture.TestSqlLoggerFactory.AssertBaseline(expected);
 

test/EFCore.Sqlite.FunctionalTests/BulkUpdates/NorthwindBulkUpdatesSqliteTest.cs

@@ -1558,6 +1558,32 @@ ORDER BY "o"."OrderID"
 """);
     }
 
+    public override async Task Update_with_select_mixed_entity_scalar_anonymous_projection(bool async)
+    {
+        await base.Update_with_select_mixed_entity_scalar_anonymous_projection(async);
+
+        AssertSql(
+            """
+@p='Updated' (Size = 7)
+
+UPDATE "Customers" AS "c"
+SET "ContactName" = @p
+""");
+    }
+
+    public override async Task Update_with_select_scalar_anonymous_projection(bool async)
+    {
+        await base.Update_with_select_scalar_anonymous_projection(async);
+
+        AssertSql(
+            """
+@p='Updated' (Size = 7)
+
+UPDATE "Customers" AS "c"
+SET "ContactName" = @p
+""");
+    }
+
     private void AssertSql(params string[] expected)
         => Fixture.TestSqlLoggerFactory.AssertBaseline(expected);