Query: Convert SubSelectExpression to search condition as necessary

src/EFCore.SqlServer/Query/Pipeline/SearchConditionConvertingExpressionVisitor.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Generic;
 using System.Linq.Expressions;
 using Microsoft.EntityFrameworkCore.Relational.Query.Pipeline;
@@ -202,7 +203,6 @@ protected override Expression VisitSqlBinary(SqlBinaryExpression sqlBinaryExpres
                     || sqlBinaryExpression.OperatorType == ExpressionType.LessThan
                     || sqlBinaryExpression.OperatorType == ExpressionType.LessThanOrEqual;
 
-
             return ApplyConversion(sqlBinaryExpression, condition);
         }
 
@@ -223,10 +223,14 @@ protected override Expression VisitSqlUnary(SqlUnaryExpression sqlUnaryExpressio
                     resultCondition = false;
                     break;
 
-                default:
+                case ExpressionType.Equal:
+                case ExpressionType.NotEqual:
                     _isSearchCondition = false;
                     resultCondition = true;
                     break;
+
+                default:
+                    throw new InvalidOperationException("Unknown operator type encountered in SqlUnaryExpression.");
             }
 
             var operand = (SqlExpression)Visit(sqlUnaryExpression.Operand);
@@ -325,9 +329,11 @@ protected override Expression VisitLeftJoin(LeftJoinExpression leftJoinExpressio
 
         protected override Expression VisitSubSelect(SubSelectExpression subSelectExpression)
         {
+            var parentSearchCondition = _isSearchCondition;
             var subquery = (SelectExpression)Visit(subSelectExpression.Subquery);
+            _isSearchCondition = parentSearchCondition;
 
-            return subSelectExpression.Update(subquery);
+            return ApplyConversion(subSelectExpression.Update(subquery), condition: false);
         }
     }
 }

test/EFCore.Specification.Tests/Query/GearsOfWarQueryTestBase.cs

@@ -7504,6 +7504,15 @@ public virtual Task Anonymous_projection_take_followed_by_projecting_single_elem
                 gs => gs.Select(g => new { Gear = g }).Take(25).Select(e => e.Gear.Weapons.OrderBy(w => w.Id).FirstOrDefault()));
         }
 
+        [ConditionalTheory]
+        [MemberData(nameof(IsAsyncData))]
+        public virtual Task Bool_projection_from_subquery_treated_appropriately_in_where(bool isAsync)
+        {
+            return AssertQuery<City, Gear>(
+                isAsync,
+                (cs, gs) => cs.Where(c => gs.OrderBy(g => g.Nickname).ThenBy(g => g.SquadId).FirstOrDefault().HasSoulPatch));
+        }
+
         protected GearsOfWarContext CreateContext() => Fixture.CreateContext();
 
         protected virtual void ClearLog()

test/EFCore.Specification.Tests/TestUtilities/TestHelpers.cs

@@ -300,8 +300,8 @@ public static int AssertResults<T>(
                 }
             }
 
-            elementSorter = elementSorter ?? (e => e);
-            elementAsserter = elementAsserter ?? Assert.Equal;
+            elementSorter ??= (e => e);
+            elementAsserter ??= Assert.Equal;
             if (!verifyOrdered)
             {
                 expected = expected.OrderBy(elementSorter).ToList();
@@ -340,7 +340,7 @@ public static int AssertResults<T>(
                 }
             }
 
-            elementAsserter = elementAsserter ?? Assert.Equal;
+            elementAsserter ??= Assert.Equal;
             if (!verifyOrdered)
             {
                 expected = expected.OrderBy(elementSorter).ToList();
@@ -380,7 +380,7 @@ public static int AssertResultsNullable<T>(
                 }
             }
 
-            elementAsserter = elementAsserter ?? Assert.Equal;
+            elementAsserter ??= Assert.Equal;
             if (!verifyOrdered)
             {
                 expected = expected.OrderBy(elementSorter).ToList();

test/EFCore.SqlServer.FunctionalTests/Query/GearsOfWarQuerySqlServerTest.cs

@@ -8565,6 +8565,20 @@ public override async Task Anonymous_projection_take_followed_by_projecting_sing
                 @"");
         }
 
+        public override async Task Bool_projection_from_subquery_treated_appropriately_in_where(bool isAsync)
+        {
+            await base.Bool_projection_from_subquery_treated_appropriately_in_where(isAsync);
+
+            AssertSql(
+                @"SELECT [c].[Name], [c].[Location], [c].[Nation]
+FROM [Cities] AS [c]
+WHERE (
+    SELECT TOP(1) [g].[HasSoulPatch]
+    FROM [Gears] AS [g]
+    WHERE [g].[Discriminator] IN (N'Gear', N'Officer')
+    ORDER BY [g].[Nickname], [g].[SquadId]) = CAST(1 AS bit)");
+        }
+
         private void AssertSql(params string[] expected)
             => Fixture.TestSqlLoggerFactory.AssertBaseline(expected);