Partially nullable composite Foreign Key is not supported

[lybax]

OData returns an incomplete (chunked) JSON response when expanding a navigation property referenced by two foreign keys, of which one is nullable and actually being null.

Assemblies affected

Microsoft.AspNetCore.OData, Version=7.1.0.21120

Reproduce steps

Model

public class SourceEntity
{
   public int ForeignKey1 { get; set; }
   public int? ForeignKey2 { get; set; }
   public virtual TargetEntity NavigationProperty { get; set; }
}

public class TargetEntity
{
   public int Key1 { get; set; }
   public int Key2 { get; set; }
}

ODataConventionalBuilder
builder.EntitySet<SourceEntity>("EntitySet").EntityType.HasOptional(x => x.NavigationProperty, (c, r) => c.ForeignKey1 == r.Key1 && c.ForeignKey2 == r.Key2);

OData query

• OK: http://localhost/odata/EntitySet?$top=1&$select=ForeignKey1,ForeignKey2&$filter=ForeignKey2%20eq%20null
• NOK: http://localhost/odata/EntitySet?$top=1&$select=ForeignKey1,ForeignKey2&$filter=ForeignKey2%20eq%20null&$expand=NavigationProperty

Expected result

Complete JSON response (HTTP Status 200 OK)
{"@odata.context":"http://localhost/odata/$metadata#EntitySet(ForeignKey1,ForeignKey2,NavigationProperty)","value":[{"ForeignKey1":1234,"ForeignKey2":null,"NavigationProperty":null}]}

Actual result

Incomplete (chunked) JSON response (HTTP Status 200 OK)
{"@odata.context":"http://localhost/odata/$metadata#EntitySet(ForeignKey1,ForeignKey2,NavigationProperty)","value":[{"ForeignKey1":1234,"ForeignKey2":null

Additional detail

A similar query in Entity Framework Core (EF Core) works correctly:

var test = DbSet<SourceEntity>().Where(x => x.ForeignKey2 == null).Take(1).Select(x => x.NavigationProperty).ToList();

By definition,

The value of a composite foreign key is null if any component of the value is null.

[lybax]

The issue comes from the generated SQL query.

With this query (which does not work):
http://localhost/odata/EntitySet?$top=1&$select=ForeignKey1,ForeignKey2&$filter=ForeignKey2%20eq%20null&$expand=NavigationProperty

We get:

exec sp_executesql N'SELECT TOP(@__TypedProperty_0) 
[$it.NavigationProperty].[ForeignKey1], 
[$it.NavigationProperty].[ForeignKey2],
[$it.NavigationProperty].[OtherProperty1], 
[$it.NavigationProperty].[OtherProperty2],
[$it].[ForeignKey1] AS [Value], 
[$it].[ForeignKey2] AS [Value0], 
CASE
    WHEN [$it].[ForeignKey1] IS NULL AND [$it].[ForeignKey2] IS NULL
    THEN CAST(1 AS BIT) ELSE CAST(0 AS BIT)
END AS [IsNull]
FROM [secured].[SourceEntities] AS [$it]
LEFT JOIN [secured].[TargetEntities] AS [$it.NavigationProperty] ON ([$it].[ForeignKey1] = [$it.NavigationProperty].[ForeignKey1]) AND ([$it].[ForeignKey2] = [$it.NavigationProperty].[ForeignKey2])
WHERE [$it].[ForeignKey2] IS NULL
ORDER BY [Value]',N'@__TypedProperty_0 int',@__TypedProperty_0=1

where [IsNull] is 0, because it compares both foreign keys with AND statement instead of OR, which is incorrect according to this statement:

The value of a composite foreign key is null if any component of the value is null.

Now using this query (which works):
http://localhost/odata/EntitySet?$top=1&$select=ForeignKey1,ForeignKey2&$filter=ForeignKey2%20eq%20null&$expand=NavigationProperty($select=Key1)

We get:

exec sp_executesql N'SELECT TOP(@__TypedProperty_0) 
[$it.NavigationProperty].[ForeignKey1] AS [Value0], 
[$it.NavigationProperty].[ForeignKey2] AS [Value], 
[$it].[ForeignKey1] AS [Value1], 
[$it].[ForeignKey2] AS [Value2], 
CASE
    WHEN [$it.NavigationProperty].[ForeignKey1] IS NULL
    THEN CAST(1 AS BIT) ELSE CAST(0 AS BIT)
END & CASE
    WHEN [$it.NavigationProperty].[ForeignKey2] IS NULL
    THEN CAST(1 AS BIT) ELSE CAST(0 AS BIT)
END AS [IsNull]
FROM [secured].[SourceEntities] AS [$it]
LEFT JOIN [secured].[TargetEntities] AS [$it.NavigationProperty] ON ([$it].[ForeignKey1] = [$it.NavigationProperty].[ForeignKey1]) AND ([$it].[ForeignKey2] = [$it.NavigationProperty].[ForeignKey2])
WHERE [$it].[ForeignKey2] IS NULL
ORDER BY [Value1]',N'@__TypedProperty_0 int',@__TypedProperty_0=1

where [IsNull] is 1, because it compares 2 fields from the joined table, which are null.