Breaking changes on ConfigurationBinder behaviour

[mapogolions]

Description

Before this changes I could convert any non-terminal section (section that doesn't have a value, but has child keys) to an array as shown the example below. This is not possible in the current implementation.

var configRoot = new ConfigurationBuilder()
    .AddInMemoryCollection(new KeyValuePair<string, string>[]
    {
        new("section:key1", "1"),
        new("section:key2", "2"),
        new("section:key3", "3")
        /**
         {
             "section": {
                 "key1": "1",
                 "key2": "2",
                 "key3": "3"
             }
         }
        */
    })
    .Build();
var values = configRoot.GetSection("section").Get<int[]>();


Assert.Equal(3, values.Length);
Assert.Equal(1, values[0]);
Assert.Equal(2, values[1]);
Assert.Equal(3, values[2]);

Other information

This line of code requires the child key (as "key1", "key2", "key3" in example above) to be an integer.

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.

Tagging subscribers to this area: @safern
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

Before this changes I could convert any non-terminal section (section that doesn't have a value, but has child keys) to an array as shown the example below. This is not possible in the current implementation.

var configRoot = new ConfigurationBuilder()
    .AddInMemoryCollection(new KeyValuePair<string, string>[]
    {
        new("section:key1", "1"),
        new("section:key2", "2"),
        new("section:key3", "3")
        /**
         {
             "section": {
                 "key1": "1",
                 "key2": "2",
                 "key3": "3"
             }
         }
        */
    })
    .Build();
var values = configRoot.GetSection("section").Get<int[]>();


Assert.Equal(3, values.Length);
Assert.Equal(1, values[0]);
Assert.Equal(2, values[1]);
Assert.Equal(3, values[2]);

Other information

This line of code requires the child key (as "key1", "key2", "key3" in example above) to be an integer.

Author:	mapogolions
Assignees:	-
Labels:	area-System.Configuration, untriaged
Milestone:	-

[mapogolions]

In my opinion, the most unexpected side effect of the introduced changes is demonstrated by the example below.

       [Fact]
        public void ShouldGetArrayOfConfigurationSections()
        {
            var configRoot = new ConfigurationBuilder()
                .AddInMemoryCollection(new KeyValuePair<string, string>[]
                {
                    new("Foo", "1"),
                    new("Bar", "2")
                })
                .Build();

            var sections = configRoot.Get<IConfigurationSection[]>();
            var fooConfigSection = sections.SingleOrDefault(x => x.Key == "Foo");
            var barConfigSection = sections.SingleOrDefault(x => x.Key == "Bar");

            Assert.Equal(2, sections.Count());
            Assert.Equal("1", fooConfigSection.Value);
            Assert.Equal("2", barConfigSection.Value);
        }

This test case will fail. As you can see now we cannot get array of sections from the configuration root.

Tagging subscribers to this area: @maryamariyan, @safern
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

Before this changes I could convert any non-terminal section (section that doesn't have a value, but has child keys) to an array as shown the example below. This is not possible in the current implementation.

var configRoot = new ConfigurationBuilder()
    .AddInMemoryCollection(new KeyValuePair<string, string>[]
    {
        new("section:key1", "1"),
        new("section:key2", "2"),
        new("section:key3", "3")
        /**
         {
             "section": {
                 "key1": "1",
                 "key2": "2",
                 "key3": "3"
             }
         }
        */
    })
    .Build();
var values = configRoot.GetSection("section").Get<int[]>();


Assert.Equal(3, values.Length);
Assert.Equal(1, values[0]);
Assert.Equal(2, values[1]);
Assert.Equal(3, values[2]);

Other information

This line of code requires the child key (as "key1", "key2", "key3" in example above) to be an integer.

Author:	mapogolions
Assignees:	-
Labels:	untriaged, area-Extensions-Configuration
Milestone:	-

[joperezr]

cc: @maryamariyan can you please take a look?

[maryamariyan]

Thanks for the feedback @mapogolions.
You could use an AppContext switch (Microsoft.Extensions.Configuration.BindSingleElementsToArray) to provide "temporary" access to the previous behavior.
We could perhaps document this breaking change explained in your sample.

[vidommet]

As @maryamariyan commented, the old behavior can be opted in. But in my opinion, the casting above doesn't make complete sense as the objects are not part of an array. The children can still be retrieved using IConfigurationSection[] section = root.GetChildren().ToArray(). It could be an unintended behavior of the old implementation.