Add feature to use reqwest with rustls/webpki_roots

[everest-boehm]

The webpki_roots crate is an alternative to the ssl certificates provided by the underlying operating system. The discovery process of the latter involves making use of the system's openssl installation on linux which in many development scenarios just isn't present. Here, webpki_roots offers a convenient way to bake certificates into the final binary.

[Copilot]

Pull Request Overview

This PR adds support for using reqwest with webpki_roots as an alternative to native system SSL certificates. The change introduces a new feature flag reqwest_rustls_webpki_roots while maintaining backward compatibility by renaming the existing reqwest_rustls feature to reqwest_rustls_native_roots and creating an alias.

Key changes:

• Introduces reqwest_rustls_webpki_roots feature for embedding certificates in the binary
• Renames reqwest_rustls to reqwest_rustls_native_roots for clarity while maintaining backward compatibility
• Updates all conditional compilation directives to include the new feature flags

Reviewed Changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
sdk/typespec/typespec_client_core/src/http/clients/mod.rs	Updates conditional compilation directives to include new rustls feature variants
sdk/typespec/typespec_client_core/README.md	Documents the new webpki_roots feature and clarifies native_roots feature
sdk/typespec/typespec_client_core/Cargo.toml	Adds feature definitions for both rustls variants with backward compatibility alias
sdk/identity/azure_identity/Cargo.toml	Updates feature mappings to use new rustls feature names
sdk/core/azure_core/README.md	Documents the new webpki_roots feature alongside existing rustls feature
sdk/core/azure_core/Cargo.toml	Adds feature pass-through definitions for both rustls variants

Comments suppressed due to low confidence (1)

sdk/identity/azure_identity/Cargo.toml:42

• The feature name reqwest_rustls_ has a trailing underscore which appears to be a typo. Based on the context and other files, this should likely be reqwest_rustls to maintain the backward compatibility alias.

reqwest_rustls_ = ["reqwest_rustls_native_roots"]

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Thank you for your contribution @everest-boehm! We will review the pull request and get back to you soon.

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[everest-boehm]

Ah, yes. webpki_roots is published under CDLA-Permissive-2.0, which is currently rejected by cargo-deny. Please advise if this is a hard blocker.

[LarryOsterman]

Ah, yes. webpki_roots is published under CDLA-Permissive-2.0, which is currently rejected by cargo-deny. Please advise if this is a hard blocker.

I'm checking to see if this is a blocking issue or not. It may take a few days to get a response, sorry about that.

[everest-boehm]

I created this repository to verify that this actually allows using the core and identity crates in linux images which don't come with openssl. Unfortunately, I was still missing some things before it could work. The crucial part was that when using the name of a dependency also as a feature, and then enabling a dependency-feature on that from another feature, the feature with the same name gets activated with it. So defining the reqwest feature as [reqwest/native-tls] makes it impossible, if I am not totally mistaken here, to use the reqwest_rustls feature without also enabling reqwest/native-tls.

The cargo book is phrased a bit ambiguously here I think

The "package-name/feature-name" syntax will also enable package-name if it is an optional dependency.

as it is unclear whether "enable package-name" here refers to a feature or dependency or both (it seems it is both).

The second big change was that I had to default-features = false the workspace azure-core crate or else we would not be able to depend on it without default features in azure-identity. It seems this can break tests elsewhere in subtle ways.

I apologize for this PR being such a mess. I honestly thought this would be a rather simple mechanical change.

[LarryOsterman]

I apologize for this PR being such a mess. I honestly thought this would be a rather simple mechanical change.

No need to apologize - Rust can be a challenge to deal with.