Configuration binding with nested types and readonly properties not working

[glucaci]

Description

With #67258 the binding of immutable types is working but with nested types seams not to work.

Reproduction Steps

public record RootConfig(NestedConfig Nested);

public record NestedConfig(string MyProp);

public RootConfig GetConfiguration()
{
    IConfiguration configuration = new ConfigurationBuilder()
        .AddInMemoryCollection(new Dictionary<string, string?>
        {
            { "Nested:MyProp", "Dummy" }
        })
        .Build();

    return configuration.Get<RootConfig>();            
}

In the above case the following exception will be thrown:

Cannot create instance of type 'RootConfig' because parameter 'Nested' has no matching config. 
Each parameter in the constructor that does not have a default value must have a corresponding config entry.

If the Nested property is declared with init modifier like bellow it will work.

public record RootConfig
{
    public NestedConfig Nested { get; init; }
}

Expected behavior

No exception.

Actual behavior

Throws InvalidOperationException.

Regression?

No response

Known Workarounds

Declare the Nested property with init modifier.

Configuration

.NET 7 RC2

Other information

No response

[ghost]

Tagging subscribers to this area: @dotnet/area-extensions-configuration
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Issue Details

---

Description

With #67258 the binding of immutable types is working but with nested types seams not to work.

Reproduction Steps

public record RootConfig(NestedConfig Nested);

public record NestedConfig(string MyProp);

public RootConfig GetConfiguration()
{
    IConfiguration configuration = new ConfigurationBuilder()
        .AddInMemoryCollection(new Dictionary<string, string?>
        {
            { "Nested:MyProp", "Dummy" }
        })
        .Build();

    return configuration.Get<RootConfig>();            
}

In the above case the following exception will be thrown:

Cannot create instance of type 'RootConfig' because parameter 'Nested' has no matching config. 
Each parameter in the constructor that does not have a default value must have a corresponding config entry.

If the Nested property is declared with init modifier like bellow it will work.

public record RootConfig
{
    public NestedConfig Nested { get; init; }
}

Expected behavior

No exception.

Actual behavior

Throws InvalidOperationException.

Regression?

No response

Known Workarounds

Declare the Nested property with init modifier.

Configuration

.NET 7 RC2

Other information

No response

Author:	glucaci
Assignees:	-
Labels:	area-Extensions-Configuration
Milestone:	-

[tarekgh]

@SteveDunn will you have some spare time to look at this one?

[SteveDunn]

@tarekgh / @glucaci - hi - I just got main and added this test and it passed without the exception described above

Admittedly, this was a very quick exercise as my time is rather limited with my day job.

Have I missed something?

(PR added - please feel free to modify it so that it breaks, and I'll attempt a fix when time permits - #77693)

[tarekgh]

@SteveDunn thanks for the follow up. I am trying that with .NET 7.0 rc2 and I am seeing it failing. I'll try the rtm bits to see if it reproduces there.

FrameworkDescription: .NET 7.0.0-rc.2.22472.3
RuntimeIdentifier: win10-x64

Unhandled exception. System.InvalidOperationException: Cannot create instance of type 'NetCoreApp.Program+RootConfig' because parameter 'Nested' has no matching config. Each parameter in the constructor that does not have a default value must have a corresponding config entry.
   at Microsoft.Extensions.Configuration.ConfigurationBinder.BindParameter(ParameterInfo parameter, Type type, IConfiguration config, BinderOptions options)
   at Microsoft.Extensions.Configuration.ConfigurationBinder.CreateInstance(Type type, IConfiguration config, BinderOptions options)
   at Microsoft.Extensions.Configuration.ConfigurationBinder.BindInstance(Type type, BindingPoint bindingPoint, IConfiguration config, BinderOptions options)
   at Microsoft.Extensions.Configuration.ConfigurationBinder.Get(IConfiguration configuration, Type type, Action`1 configureOptions)
   at Microsoft.Extensions.Configuration.ConfigurationBinder.Get[T](IConfiguration configuration, Action`1 configureOptions)
   at Microsoft.Extensions.Configuration.ConfigurationBinder.Get[T](IConfiguration configuration)
   at NetCoreApp.Program.BindWithNestedTypesWithReadOnlyProperties() in C:\Temp\NetCoreApp\Program.cs:line 114
   at NetCoreApp.Program.Main(String[] args) in C:\Temp\NetCoreApp\Program.cs:line 159

[tarekgh]

Interesting, it looks something has been changed in .NET 8.0 which fixed the issue. We need to understand what has changed.

[SteveDunn]

It is this:

Left is RC2, right is Main as of yesterday (31st October '22)

The commit on the right is ca0d3e4d by @Saalvage

I'm happy if you want to close this PR.

[SteveDunn]

Actually, it might be worth merging in as the test is useful as a regression.

[glucaci]

It is this:

Left is RC2, right is Main as of yesterday (31st October '22)

The commit on the right is ca0d3e4d by @Saalvage

I'm happy if you want to close this PR.

@tarekgh could this be cherry-picked into .NET 7?

[tarekgh]

Actually, it might be worth merging in as the test is useful as a regression.

Agree. Thanks for pointing at the change that fixed this issue.

could this be cherry-picked into .NET 7?

.NET 7.0 is done. It is going to be released in a few days. We may consider servicing this later if proven it is a blocker to important scenarios. Considering the workaround is trivial and it is not a regression, this will be difficult to meet the servicing bar.

[aradalvand]

Just encountered the same problem; such a shame that the fix didn't make it to 7.0...

Considering the workaround is trivial

What is the workaround, please?

[tarekgh]

@aradalvand

In the issue description, it mentioned the following

Known Workarounds
Declare the Nested property with init modifier.