Deprecate cURL

[das-sein]

Part of the simplification project: #1611

Deprecates cURL in favor of reqwest.

This is the preliminary step for the complete disuse of cURL by rustup; on-going discussion: #1657

cc's from previous PR:
@dwijnand
@brson
@briansmith
@jnicholls
@seanmonstar

[dwijnand]

I don't think RUSTUP_USE_CURL should be introduced and on usage it emits a warning message. I think the old UsingCurl notification should remain.

[das-sein]

@dwijnand Does this mean we should have the user compile themselves with the default feature in the Cargo.toml set to cURL if they want to use it?

[dwijnand]

No, no compilation necessary, as the rustup binary crate depends on both backends/features:

https://github.com/rust-lang/rustup.rs/blob/194026d2cac3d06c8ef19dc6e23dabda5d3900c4/Cargo.toml#L23

[das-sein]

How would a user enable one backend over the other without some kind of environment variable? I think I'm missing something here.

[dwijnand]

Ah, I see the confusion. I meant we should introduce RUSTUP_USE_CURL but, if a user sets it, it shouldn't emit a deprecation warning message. Just "downloading with curl".

[das-sein]

@dwijnand Removed the deprecation warning.

[dwijnand]

LGTM. Thanks!

[kinnison]

This is good, though I'd prefer the odd bogon of a diff hunk was fixed.

[das-sein]

@kinnison Weird delta removed from commits.

[nrc]

LGTM other than the Hyper thing

Odd bogon of a diff hunk fixed

[acid-bong]

Hi there, hello. How safe would it be to drop Curl from dependencies, when building packages for different distros?

By glancing at big distros and OSes at Repology, I found out only OpenSUSE and FreeBSD compile Rustup without Curl, and I'm currently thinking about dropping that dependency in Nixpkgs (the relevant PR is linked above)

[rami3l]

@acid-bong Hello, and thanks for your interest!

As clarified in #4296, we will be dropping the cURL backend soon anyway, so I don't think it'll be extremely helpful to keep supporting it: we are currently keeping it just in case someone has a very particular system environment, and starting from the next release we'll be issuing a warning for them to report to our issue tracker.

PS: We have shipped since v1.28.0 UA-based tracking for backend usages, but I might need to refer to @rust-lang/infra for the real proportion of users using the cURL backend... Hopefully it'll be reasonably small.

[djc]

@decathorpe would be curious to hear your feedback/thoughts! And maybe @sylvestre?

[decathorpe]

@decathorpe would be curious to hear your feedback/thoughts!

I see no problems with dropping the cURL backend in favor of reqwest. The Fedora package will most likely just follow the rustup upstream preference here, if that's why you tagged me :)

[sylvestre]

I think we (in Debian) will be fine :)

[djc]

@decathorpe would be curious to hear your feedback/thoughts!

I see no problems with dropping the cURL backend in favor of reqwest. The Fedora package will most likely just follow the rustup upstream preference here, if that's why you tagged me :)

Sounds good! Are you defaulting rustup to native-tls over rustls today?

[decathorpe]

@decathorpe would be curious to hear your feedback/thoughts!

I see no problems with dropping the cURL backend in favor of reqwest. The Fedora package will most likely just follow the rustup upstream preference here, if that's why you tagged me :)

Sounds good! Are you defaulting rustup to native-tls over rustls today?

No, the only feature flag we pass for our build is to enable no-self-update, otherwise it follows defaults.