Spatial and data seeding: Migration generates files with concrete class (e.g. Point) instead of interface (e.g. IPoint) and do not compile

[divega]

Repro steps:

1. Create project using IPoint, e.g.:

using System;
using System.Linq;
using GeoAPI.Geometries;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using NetTopologySuite;

namespace Demos
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            using (var context = new SensorContext())
            {
                Console.ReadLine();
            }

            using (var context = new SensorContext())
            {
                var currentLocation = context.GeometryFactory.CreatePoint(new Coordinate(0, 0));

                // Step 2: To use tag in follow query add following code after context.Measurements
                // .TagWith("This is my spatial query!")
                var nearestMesurements =
                    (from m in context.Measurements.TagWith("This is my spatial query!")
                    where m.Location.Distance(currentLocation) < 2.5
                    orderby m.Location.Distance(currentLocation) descending
                    select m).Take(5);

                foreach (var m in nearestMesurements)
                {
                    Console.WriteLine($"A temperature of {m.Temperature} was detected on {m.Time} at {m.Location}.");
                }
            }
        }
    }

    public class SensorContext : DbContext
    {
        private static readonly IGeometryFactory _geometryFactory = 
            NtsGeometryServices.Instance.CreateGeometryFactory(srid: 4326);

        private static readonly ILoggerFactory _loggerFactory = new LoggerFactory()
            .AddConsole((s, l) => l == LogLevel.Information && s.EndsWith("Command"));

        public IGeometryFactory GeometryFactory => _geometryFactory;

        public DbSet<Measurement> Measurements { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder
                .UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=Demo.Spatial;Trusted_Connection=True;ConnectRetryCount=0",
                        sqlOptions => sqlOptions.UseNetTopologySuite())
                .UseLoggerFactory(_loggerFactory);
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Measurement>().HasData(
              new Measurement {Id = 1, Time = DateTime.Now, Location = GeometryFactory.CreatePoint(new Coordinate(0, 0)), Temperature = 0.0 },
              new Measurement {Id = 2, Time = DateTime.Now, Location = GeometryFactory.CreatePoint(new Coordinate(1, 1)), Temperature = 0.1 },
              new Measurement {Id = 3, Time = DateTime.Now, Location = GeometryFactory.CreatePoint(new Coordinate(1, 2)), Temperature = 0.2 },
              new Measurement {Id = 4, Time = DateTime.Now, Location = GeometryFactory.CreatePoint(new Coordinate(2, 1)), Temperature = 0.3 },
              new Measurement {Id = 5, Time = DateTime.Now, Location = GeometryFactory.CreatePoint(new Coordinate(2, 2)), Temperature = 0.4 });
        }

    }

    public class Measurement
    {
        public int Id { get; set; }
        public DateTime Time { get; set; }
        public IPoint Location { get; set; }
        public double Temperature { get; set; }
    }
}

2. Add a migration
3. Try to build

Expected:
Only the GeoAPI.Geometries namespace should be imported in all generated files, and the type IPoint should be used for any necessary casts.

Actual:
All files use Point instead of IPoint. The migration file imports the NetTopologySuite.Geometries (probably incorrectly) which means type Point does resolve, but .Designer and snapshot files only import the GeoAPI.Geometries (correctly) but and incorrectly use Point instead of IPoint.

[ajcvickers]

@bricelam @divega I investigated this and the root cause is two fold:

• The interface type used for the property is not always available, most notably in HasData where type mapping is for the concrete type used in the HasData call.
• The type used in the final cast of the literal expression is not always a type for which there is already a using directive. This is coupled to there being currently no way to generate a using based on the types used in this Expression.

Ideally, the best way to fix this is to allow the literal generation to influence the using statements generated. This would also stop us from fully-qualifying other types here, such as the factory. However, this looks non-trivial to do and probably not something we should do for 2.2. For 2.2, we can just start fully qualifying the cast.

I'll send a PR for the latter, but we can discuss tomorrow.

[divega]

@ajcvickers sounds reasonable.

[ajcvickers]

See also #13799