ConfigurationBinder.Bind is not linker friendly

[benaadams]

If Configuration.Bind is called on a type an it is the only method of setting its properties all the properties will be removed at link time and the configuration then will not set for bind

runtime/src/libraries/Microsoft.Extensions.Configuration.Binder/src/ConfigurationBinder.cs

Line 107 in 6072e4d

public static void Bind(this IConfiguration configuration, object instance, Action<BinderOptions> configureOptions)

Repo, link with <TrimMode>Link</TrimMode>

using Microsoft.Extensions.Configuration;
using System;
using System.Collections.Generic;

var config = new ConfigurationBuilder()
            .AddInMemoryCollection(new[]
            {
                KeyValuePair.Create("Value", "100")
            })
            .Build();
var poco = new Poco();
config.Bind(poco);

Console.WriteLine(poco.Value);

public class Poco
{
    public int Value { get; set; }
}

Will output 0 rather than 100

This issue currently occurs for certificates in Kestrel dotnet/aspnetcore#25482 meaning https certs cannot be set via config if ASP.NET Core is trimmed; also for IdentityServer.Configuration.KeyDefinition as they both use .Bind(value)

[Dotnet-GitSync-Bot]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[campersau]

Similar to #40551

[davidfowl]

cc @eerhardt

[eerhardt]

Duplicate of #40551. Closing.

[davidfowl]

Similar but not the same. The other issue there's a type parameter, this is an object parameter. This also isn't about object creation but about the fact that property setters get removed.

[eerhardt]

The other issue covers that the whole assembly isn't linker-safe.

[davidfowl]

It doesn't call out this problem in the description of the issue. Basically anything that uses config binding is busted in a very specific way (recursive properties or not).

[eerhardt]

The second paragraph of #40551 states:

The linker could decide to trim property setters and constructors which would cause the binder to not set properties correctly.

And the title of the issue is "Microsoft.Extensions.Configuration.Binder is not linker-safe".

I don't see any reason why we would need to keep 2 issues open to track the same problem.