[release/10.0] Fix empty scalar collection support

src/EFCore.Relational/Query/SqlNullabilityProcessor.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections;
+using System.Collections.ObjectModel;
 using System.Diagnostics.CodeAnalysis;
 using Microsoft.EntityFrameworkCore.Query.SqlExpressions;
 
@@ -28,6 +29,9 @@ public class SqlNullabilityProcessor : ExpressionVisitor
     /// </summary>
     private readonly Dictionary<SqlParameterExpression, List<SqlParameterExpression>> _collectionParameterExpansionMap;
 
+    private static readonly bool UseOldBehavior37216 =
+        AppContext.TryGetSwitch("Microsoft.EntityFrameworkCore.Issue37216", out var enabled) && enabled;
+
     /// <summary>
     ///     Creates a new instance of the <see cref="SqlNullabilityProcessor" /> class.
     /// </summary>
@@ -185,6 +189,33 @@ protected override Expression VisitExtension(Expression node)
                         throw new UnreachableException();
                 }
 
+                // We've inlined the user-provided collection from the values parameter into the SQL VALUES expression: (VALUES (1), (2)...).
+                // However, if the collection happens to be empty, this doesn't work as VALUES does not support empty sets. We convert it
+                // to a SELECT ... WHERE false to produce an empty result set instead.
+                if (!UseOldBehavior37216 && processedValues.Count == 0)
+                {
+                    var select = new SelectExpression(
+                        valuesExpression.Alias,
+                        tables: [],
+                        predicate: new SqlConstantExpression(false, Dependencies.TypeMappingSource.FindMapping(typeof(bool))),
+                        groupBy: [],
+                        having: null,
+                        projections: valuesExpression.ColumnNames
+                            .Select(n => new ProjectionExpression(
+                                new SqlConstantExpression(value: null, elementTypeMapping.ClrType, elementTypeMapping), n))
+                            .ToList(),
+                        distinct: false,
+                        orderings: [],
+                        offset: null,
+                        limit: null,
+                        tags: ReadOnlySet<string>.Empty,
+                        annotations: null,
+                        sqlAliasManager: null!,
+                        isMutable: false);
+
+                    return select;
+                }
+
                 return valuesExpression.Update(processedValues);
             }
 

test/EFCore.Cosmos.FunctionalTests/Query/PrimitiveCollectionsQueryCosmosTest.cs

@@ -777,6 +777,28 @@ WHERE ARRAY_CONTAINS(@ints, c["Int"])
 """);
     }
 
+    public override async Task Parameter_collection_empty_Contains()
+    {
+        await base.Parameter_collection_empty_Contains();
+
+        AssertSql(
+            """
+@ints='[]'
+
+SELECT VALUE c
+FROM root c
+WHERE ARRAY_CONTAINS(@ints, c["Int"])
+""");
+    }
+
+    public override async Task Parameter_collection_empty_Join()
+    {
+        // Cosmos join support. Issue #16920.
+        await AssertTranslationFailed(base.Parameter_collection_empty_Join);
+
+        AssertSql();
+    }
+
     public override async Task Parameter_collection_Contains_with_EF_Constant()
     {
         // #34327

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

@@ -458,6 +458,26 @@ await AssertQuery(
             assertEmpty: true);
     }
 
+    [ConditionalFact]
+    public virtual async Task Parameter_collection_empty_Contains()
+    {
+        int[] ints = [];
+
+        await AssertQuery(
+            ss => ss.Set<PrimitiveCollectionsEntity>().Where(c => ints.Contains(c.Int)),
+            assertEmpty: true);
+    }
+
+    [ConditionalFact] // #37216
+    public virtual async Task Parameter_collection_empty_Join()
+    {
+        int[] ints = [];
+
+        await AssertQuery(
+            ss => ss.Set<PrimitiveCollectionsEntity>().Join(ints, e => e.Id, i => i, (e, i) => e),
+            assertEmpty: true);
+    }
+
     [ConditionalFact]
     public virtual Task Parameter_collection_Contains_with_EF_Constant()
     {

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

@@ -768,6 +768,33 @@ FROM [PrimitiveCollectionsEntity] AS [p]
 """);
     }
 
+    public override async Task Parameter_collection_empty_Contains()
+    {
+        await base.Parameter_collection_empty_Contains();
+
+        AssertSql(
+            """
+SELECT [p].[Id], [p].[Bool], [p].[Bools], [p].[DateTime], [p].[DateTimes], [p].[Enum], [p].[Enums], [p].[Int], [p].[Ints], [p].[NullableInt], [p].[NullableInts], [p].[NullableString], [p].[NullableStrings], [p].[NullableWrappedId], [p].[NullableWrappedIdWithNullableComparer], [p].[String], [p].[Strings], [p].[WrappedId]
+FROM [PrimitiveCollectionsEntity] AS [p]
+WHERE 0 = 1
+""");
+    }
+
+    public override async Task Parameter_collection_empty_Join()
+    {
+        await base.Parameter_collection_empty_Join();
+
+        AssertSql(
+            """
+SELECT [p].[Id], [p].[Bool], [p].[Bools], [p].[DateTime], [p].[DateTimes], [p].[Enum], [p].[Enums], [p].[Int], [p].[Ints], [p].[NullableInt], [p].[NullableInts], [p].[NullableString], [p].[NullableStrings], [p].[NullableWrappedId], [p].[NullableWrappedIdWithNullableComparer], [p].[String], [p].[Strings], [p].[WrappedId]
+FROM [PrimitiveCollectionsEntity] AS [p]
+INNER JOIN (
+    SELECT NULL AS [Value]
+    WHERE 0 = 1
+) AS [p0] ON [p].[Id] = [p0].[Value]
+""");
+    }
+
     public override async Task Parameter_collection_Contains_with_EF_Constant()
     {
         await base.Parameter_collection_Contains_with_EF_Constant();

test/EFCore.SqlServer.FunctionalTests/Query/PrimitiveCollectionsQuerySqlServer160Test.cs

@@ -762,6 +762,33 @@ FROM [PrimitiveCollectionsEntity] AS [p]
 """);
     }
 
+    public override async Task Parameter_collection_empty_Contains()
+    {
+        await base.Parameter_collection_empty_Contains();
+
+        AssertSql(
+            """
+SELECT [p].[Id], [p].[Bool], [p].[Bools], [p].[DateTime], [p].[DateTimes], [p].[Enum], [p].[Enums], [p].[Int], [p].[Ints], [p].[NullableInt], [p].[NullableInts], [p].[NullableString], [p].[NullableStrings], [p].[NullableWrappedId], [p].[NullableWrappedIdWithNullableComparer], [p].[String], [p].[Strings], [p].[WrappedId]
+FROM [PrimitiveCollectionsEntity] AS [p]
+WHERE 0 = 1
+""");
+    }
+
+    public override async Task Parameter_collection_empty_Join()
+    {
+        await base.Parameter_collection_empty_Join();
+
+        AssertSql(
+            """
+SELECT [p].[Id], [p].[Bool], [p].[Bools], [p].[DateTime], [p].[DateTimes], [p].[Enum], [p].[Enums], [p].[Int], [p].[Ints], [p].[NullableInt], [p].[NullableInts], [p].[NullableString], [p].[NullableStrings], [p].[NullableWrappedId], [p].[NullableWrappedIdWithNullableComparer], [p].[String], [p].[Strings], [p].[WrappedId]
+FROM [PrimitiveCollectionsEntity] AS [p]
+INNER JOIN (
+    SELECT NULL AS [Value]
+    WHERE 0 = 1
+) AS [p0] ON [p].[Id] = [p0].[Value]
+""");
+    }
+
     public override async Task Parameter_collection_Contains_with_EF_Constant()
     {
         await base.Parameter_collection_Contains_with_EF_Constant();

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

@@ -966,6 +966,33 @@ FROM [PrimitiveCollectionsEntity] AS [p]
 """);
     }
 
+    public override async Task Parameter_collection_empty_Contains()
+    {
+        await base.Parameter_collection_empty_Contains();
+
+        AssertSql(
+            """
+SELECT [p].[Id], [p].[Bool], [p].[Bools], [p].[DateTime], [p].[DateTimes], [p].[Enum], [p].[Enums], [p].[Int], [p].[Ints], [p].[NullableInt], [p].[NullableInts], [p].[NullableString], [p].[NullableStrings], [p].[NullableWrappedId], [p].[NullableWrappedIdWithNullableComparer], [p].[String], [p].[Strings], [p].[WrappedId]
+FROM [PrimitiveCollectionsEntity] AS [p]
+WHERE 0 = 1
+""");
+    }
+
+    public override async Task Parameter_collection_empty_Join()
+    {
+        await base.Parameter_collection_empty_Join();
+
+        AssertSql(
+            """
+SELECT [p].[Id], [p].[Bool], [p].[Bools], [p].[DateTime], [p].[DateTimes], [p].[Enum], [p].[Enums], [p].[Int], [p].[Ints], [p].[NullableInt], [p].[NullableInts], [p].[NullableString], [p].[NullableStrings], [p].[NullableWrappedId], [p].[NullableWrappedIdWithNullableComparer], [p].[String], [p].[Strings], [p].[WrappedId]
+FROM [PrimitiveCollectionsEntity] AS [p]
+INNER JOIN (
+    SELECT NULL AS [Value]
+    WHERE 0 = 1
+) AS [p0] ON [p].[Id] = [p0].[Value]
+""");
+    }
+
     public override async Task Column_collection_of_ints_Contains()
     {
         await base.Column_collection_of_ints_Contains();

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

@@ -785,6 +785,33 @@ FROM [PrimitiveCollectionsEntity] AS [p]
 """);
     }
 
+    public override async Task Parameter_collection_empty_Contains()
+    {
+        await base.Parameter_collection_empty_Contains();
+
+        AssertSql(
+            """
+SELECT [p].[Id], [p].[Bool], [p].[Bools], [p].[DateTime], [p].[DateTimes], [p].[Enum], [p].[Enums], [p].[Int], [p].[Ints], [p].[NullableInt], [p].[NullableInts], [p].[NullableString], [p].[NullableStrings], [p].[NullableWrappedId], [p].[NullableWrappedIdWithNullableComparer], [p].[String], [p].[Strings], [p].[WrappedId]
+FROM [PrimitiveCollectionsEntity] AS [p]
+WHERE 0 = 1
+""");
+    }
+
+    public override async Task Parameter_collection_empty_Join()
+    {
+        await base.Parameter_collection_empty_Join();
+
+        AssertSql(
+            """
+SELECT [p].[Id], [p].[Bool], [p].[Bools], [p].[DateTime], [p].[DateTimes], [p].[Enum], [p].[Enums], [p].[Int], [p].[Ints], [p].[NullableInt], [p].[NullableInts], [p].[NullableString], [p].[NullableStrings], [p].[NullableWrappedId], [p].[NullableWrappedIdWithNullableComparer], [p].[String], [p].[Strings], [p].[WrappedId]
+FROM [PrimitiveCollectionsEntity] AS [p]
+INNER JOIN (
+    SELECT NULL AS [Value]
+    WHERE 0 = 1
+) AS [p0] ON [p].[Id] = [p0].[Value]
+""");
+    }
+
     public override async Task Parameter_collection_Contains_with_EF_Constant()
     {
         await base.Parameter_collection_Contains_with_EF_Constant();

test/EFCore.Sqlite.FunctionalTests/Query/PrimitiveCollectionsQuerySqliteTest.cs

@@ -773,6 +773,33 @@ WHERE 0
 """);
     }
 
+    public override async Task Parameter_collection_empty_Contains()
+    {
+        await base.Parameter_collection_empty_Contains();
+
+        AssertSql(
+            """
+SELECT "p"."Id", "p"."Bool", "p"."Bools", "p"."DateTime", "p"."DateTimes", "p"."Enum", "p"."Enums", "p"."Int", "p"."Ints", "p"."NullableInt", "p"."NullableInts", "p"."NullableString", "p"."NullableStrings", "p"."NullableWrappedId", "p"."NullableWrappedIdWithNullableComparer", "p"."String", "p"."Strings", "p"."WrappedId"
+FROM "PrimitiveCollectionsEntity" AS "p"
+WHERE 0
+""");
+    }
+
+    public override async Task Parameter_collection_empty_Join()
+    {
+        await base.Parameter_collection_empty_Join();
+
+        AssertSql(
+            """
+SELECT "p"."Id", "p"."Bool", "p"."Bools", "p"."DateTime", "p"."DateTimes", "p"."Enum", "p"."Enums", "p"."Int", "p"."Ints", "p"."NullableInt", "p"."NullableInts", "p"."NullableString", "p"."NullableStrings", "p"."NullableWrappedId", "p"."NullableWrappedIdWithNullableComparer", "p"."String", "p"."Strings", "p"."WrappedId"
+FROM "PrimitiveCollectionsEntity" AS "p"
+INNER JOIN (
+    SELECT NULL AS "Value"
+    WHERE 0
+) AS "p0" ON "p"."Id" = "p0"."Value"
+""");
+    }
+
     public override async Task Parameter_collection_Contains_with_EF_Constant()
     {
         await base.Parameter_collection_Contains_with_EF_Constant();