AddEnvironmentVariables(prefix) - prefix is not respected by generic host

[legezam]

Describe the bug

.AddEnvironmentVariables(string prefix) behaves inconsistently when used in .NET generic host.

When creating a plain ConfigurationBuilder and calling .AddEnvironmentVariables(prefix) or combining it with a ServiceCollection, the provided prefix value is respected. If all the above is inside a .NET Generic Host builder, the prefix somehow gets ignored. Confirmed on .NET 5, linux (fedora) and OSX.

To Reproduce

https://gist.github.com/legezam/44343abf8649b2900f7214020d82aa5e

The above code will be sufficient to reproduce the inconsistency.

Use this for appsettings.json:

{
    "Defaults": {
        "Instance": "NOT OK"
    }
}

run this from terminal:
env foo_Defaults__Instance=foo dotnet run

I expect the following output:

foo
foo
foo

Instead i get:

NOT OK
foo
foo

Exceptions (if any)

• no

Further technical details

   dotnet --info
.NET SDK (reflecting any global.json):
 Version:   6.0.100
 Commit:    9e8b04bbff

Runtime Environment:
 OS Name:     fedora
 OS Version:  35
 OS Platform: Linux
 RID:         fedora.35-x64
 Base Path:   /home/bela/.local/share/dotnet/sdk/6.0.100/

Host (useful for support):
  Version: 6.0.0
  Commit:  4822e3c3aa

.NET SDKs installed:
  3.0.103 [/home/bela/.local/share/dotnet/sdk]
  3.1.409 [/home/bela/.local/share/dotnet/sdk]
  5.0.101 [/home/bela/.local/share/dotnet/sdk]
  5.0.200 [/home/bela/.local/share/dotnet/sdk]
  5.0.300 [/home/bela/.local/share/dotnet/sdk]
  6.0.100 [/home/bela/.local/share/dotnet/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 5.0.6 [/home/bela/.local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.0 [/home/bela/.local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 5.0.6 [/home/bela/.local/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.0 [/home/bela/.local/share/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET runtimes or SDKs:
  https://aka.ms/dotnet-download

restricting the project to use 5.0.300, through global.json. No IDE is involved, running from terminal.

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.

[KalleOlaviNiemitalo]

Does the same happen if you use new HostBuilder() instead of Host.CreateDefaultBuilder(), which already prepares to use environment variables?

[legezam]

Does the same happen if you use new HostBuilder() instead of Host.CreateDefaultBuilder(), which already prepares to use environment variables?

@KalleOlaviNiemitalo , thanks for the suggestion, it works!

Is this still an issue from sdk perspective?

[legezam]

I believe it is, from user perspective, if i am able to call .ConfigureHostConfiguration and call .AddEnvironmentVariables(prefix) without an exception being thrown by the underlying library, then i would expect my actions to have effect

[KalleOlaviNiemitalo]

It seems to be working as designed, then.
I'm not very familiar with the hosting APIs, though.

If you want to use CreateDefaultBuilder so that your app can benefit from the other default services, perhaps you can also explicitly remove the default EnvironmentVariablesConfigurationSource from the IConfigurationBuilder… well, apparently not reliably, because the IConfigurationBuilder.Sources implementation in WebAssemblyHostConfiguration returns a read-only collection.

[legezam]

Actually, i did further experiments and can have the cake and eat it too:

• using DefaultBuilder, i get all the default functionality it provides
• but instead of ConfigureHostConfiguration, if i use ConfigureAppConfiguration, prefixes are respected in there

(i am not sure anymore what is expected, but it works :) )

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

Issue Details

---

Describe the bug

.AddEnvironmentVariables(string prefix) behaves inconsistently when used in .NET generic host.

When creating a plain ConfigurationBuilder and calling .AddEnvironmentVariables(prefix) or combining it with a ServiceCollection, the provided prefix value is respected. If all the above is inside a .NET Generic Host builder, the prefix somehow gets ignored. Confirmed on .NET 5, linux (fedora) and OSX.

To Reproduce

https://gist.github.com/legezam/44343abf8649b2900f7214020d82aa5e

The above code will be sufficient to reproduce the inconsistency.

Use this for appsettings.json:

{
    "Defaults": {
        "Instance": "NOT OK"
    }
}

run this from terminal:
env foo_Defaults__Instance=foo dotnet run

I expect the following output:

foo
foo
foo

Instead i get:

NOT OK
foo
foo

Exceptions (if any)

• no

Further technical details

   dotnet --info
.NET SDK (reflecting any global.json):
 Version:   6.0.100
 Commit:    9e8b04bbff

Runtime Environment:
 OS Name:     fedora
 OS Version:  35
 OS Platform: Linux
 RID:         fedora.35-x64
 Base Path:   /home/bela/.local/share/dotnet/sdk/6.0.100/

Host (useful for support):
  Version: 6.0.0
  Commit:  4822e3c3aa

.NET SDKs installed:
  3.0.103 [/home/bela/.local/share/dotnet/sdk]
  3.1.409 [/home/bela/.local/share/dotnet/sdk]
  5.0.101 [/home/bela/.local/share/dotnet/sdk]
  5.0.200 [/home/bela/.local/share/dotnet/sdk]
  5.0.300 [/home/bela/.local/share/dotnet/sdk]
  6.0.100 [/home/bela/.local/share/dotnet/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 5.0.6 [/home/bela/.local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.0 [/home/bela/.local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 5.0.6 [/home/bela/.local/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.0 [/home/bela/.local/share/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET runtimes or SDKs:
  https://aka.ms/dotnet-download

restricting the project to use 5.0.300, through global.json. No IDE is involved, running from terminal.

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

[maryamariyan]

Actually, i did further experiments and can have the cake and eat it too:
using DefaultBuilder, i get all the default functionality it provides
but instead of ConfigureHostConfiguration, if i use ConfigureAppConfiguration, prefixes are respected in there

Seems like this issue can be closed then.