Parameter for collection of enum values contains ints even when correlated column has strings

[ajcvickers]

using (var context = new SomeDbContext())
{
    context.Database.EnsureDeleted();
    context.Database.EnsureCreated();

    var terrains = new[] { Terrain.River, Terrain.Beach, Terrain.Park };
    var walksWithTerrain = await context.Walks
        .Where(e => terrains.Contains(e.Terrain))
        .ToListAsync();
}

public class DogWalk
{
    public int Id { get; set; }
    public Terrain Terrain { get; set; }
}

public enum Terrain
{
    Forest,
    River,
    Hills,
    Village,
    Park,
    Beach,
}

public class SomeDbContext : DbContext
{
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseSqlServer(@"Data Source=(LocalDb)\MSSQLLocalDB;Database=AllTogetherNow")
            .LogTo(Console.WriteLine, LogLevel.Information)
            .EnableSensitiveDataLogging();

    public DbSet<DogWalk> Walks => Set<DogWalk>();

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<DogWalk>().Property(e => e.Terrain).HasConversion<string>();
    }
}

Parameter value below should be ["River", "Beach", "Park"]:

info: 5/18/2023 10:32:12.104 RelationalEventId.CommandExecuted[20101] (Microsoft.EntityFrameworkCore.Database.Command)
      Executed DbCommand (40ms) [Parameters=[@__terrains_0='[1,5,4]' (Size = 4000)], CommandType='Text', CommandTimeout='30']
      SELECT [w].[Id], [w].[Terrain]
      FROM [Walks] AS [w]
      WHERE EXISTS (
          SELECT 1
          FROM OpenJson(@__terrains_0) AS [t]
          WHERE [t].[value] = [w].[Terrain])

[roji]

I looked into it, and the type mapping is correctly inferred from e.Terrain and applied to the parameter collection. However, we currently just hand the collection to JsonSerializer within CollectionToJsonStringConverter - we currently effectively ignore the element type mapping when writing the parameter.

When JSON serialization/deserialization is properly implemented (#30677), we'll build up the parameter JSON string with that, at which point everything should be fine.

We can keep this open to remember to test this specific scenario, or just close it as a dup.

[be-marks]

Just want to raise a concern as early as possible here - this bug changes the output of .Contains queries we wrote as early as EF Core 5. This prevents us from using 8 until fixed but we're at least aware of the bug - if this goes out as-is in GA many users could upgrade and be unaware

#30677 is currently tagged "type-enhancement" and "needs-design". We're already at preview 4 so I'm nervous that this is a prerequisite - especially if this is closed as a dup

Thanks!

[roji]

@be-marks we absolutely intend to get this working before 8.0 GA.

[roji]

@be-marks also, just to make sure that you're aware: you can configure the SQL compatibility level to an old level (as per the blog post) to make EF switch back to the older SQL. This should allow you to continue using previews even before we fix this (the compatibility level doesn't currently affect anything else).

[ajcvickers]

Verified fixed:

info: 9/8/2023 13:08:58.838 RelationalEventId.CommandExecuted[20101] (Microsoft.EntityFrameworkCore.Database.Command) 
      Executed DbCommand (29ms) [Parameters=[@__terrains_0='["River","Beach","Park"]' (Size = 4000)], CommandType='Text', CommandTimeout='30']
      SELECT [w].[Id], [w].[Terrain]
      FROM [Walks] AS [w]
      WHERE [w].[Terrain] IN (
          SELECT [t].[value]
          FROM OPENJSON(@__terrains_0) WITH ([value] nvarchar(max) '$') AS [t]
      )