[API Proposal]: YAML configuration provider

[stasberkov]

Background and motivation

Currently, ASP.NET Core supports configuration providers for JSON, XML, and INI files. However, YAML is a popular configuration format due to its readability and support for complex data structures. Adding a YAML configuration provider would enhance the flexibility and usability of ASP.NET Core applications, especially for developers who prefer or require YAML for their configuration needs.

Benefits:

• Increased flexibility in configuration file formats.
• Improved readability and maintainability of configuration files for developers who prefer YAML.
• Enhanced support for complex configuration scenarios.

YAML is widely used in various applications and tools, such as Kubernetes and Ansible, making it a valuable addition to the ASP.NET Core configuration system. By supporting YAML, ASP.NET Core can better align with the preferences and needs of a broader developer community.

API Proposal

builder.Configuration
    .AddYamlFile("appsettings.yaml", optional: false, reloadOnChange: true)
    .AddYamlFile($"appsettings.{builder.Environment.EnvironmentName}.yaml", optional: true, reloadOnChange: true);

API Usage

builder.Configuration
    .AddYamlFile("appsettings.yaml", optional: false, reloadOnChange: true)
    .AddYamlFile($"appsettings.{builder.Environment.EnvironmentName}.yaml", optional: true, reloadOnChange: true);

Alternative Designs

No response

Risks

No response

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[am11]

Currently, runtime libraries do not offer built-in support for YAML serialization, which is the prerequisite of this feature request. However, there are community-driven YAML serialization packages like YamlDotNet, which serve as the foundation for various extensions, such as NetEscapades.Configuration.Yaml (https://www.nuget.org/packages/NetEscapades.Configuration.Yaml) and SharpDotYaml.Extensions.Configuration (https://www.nuget.org/packages/SharpDotYaml.Extensions.Configuration). Do these options meet the requirements of your use case?

[stasberkov]

Yeah, I saw these libs. I would like to minimize dependency on 3rd party libs for core functionality. I believe configuration is a part of application core.

[am11]

I would like to minimize dependency on 3rd party libs for core functionality.

See this discussion #83313 (comment), generally third party libraries is the way to go when it comes to YAML. #83313 is the prerequisite, and other similar proposals before that (which were not accepted).

[StephenHodgson]

As much as I'd love to see a native yaml parser in .net, I think since json is a subset of yaml, probably better to just use the json format for this specific purpose.

That being said most people prefer yaml for configuration files.