Add infrastructure for nightly features and flags #4433

alexcrichton · 2017-08-24T22:09:31Z

This PR starts adding infrastructure in Cargo for nightly features and nightly flags. The current design looks like:

There's a new package.cargo-features manifest key which accepts an array of strings. This array of strings is the list of enabled Cargo features for that crate.
A new suite of flags behind -Z, like the compiler, are accepted on the command line for all commands.
Features and unstable flags in Cargo are required to be used on Cargo's nightly channel, which is the same as Rust's nightly channel.
Features and unstable flags cannot be used on the stable/beta channels of Rust/Cargo.
Crates which enable features in their manifest are disallowed from being published to crates.io

The motivation behind this support is unblock a number of efforts in Cargo by allowing them to safely get implemented behind a nightly feature gate. Once behind a feature gate they can iterate in-tree without having to worry about "insta stability" and we can also get valuable usage feedback about upstream users.

Closes #4409

rust-highfive · 2017-08-24T22:09:35Z

r? @matklad

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alexcrichton · 2017-08-24T22:10:00Z

cc @rust-lang/cargo

matklad

Looks good to me, only cosmetic comments!

matklad · 2017-08-24T22:16:58Z

src/bin/bench.rs

@@ -72,6 +73,7 @@ Options:
    --no-fail-fast               Run all benchmarks regardless of failure
    --frozen                     Require Cargo.lock and cache are up to date
    --locked                     Require Cargo.lock is up to date
+    -Z FLAG ...                  Unstable (nightly-only) flags to Cargo


It's possible that it's better to hide this from help, just to avoid having the unstable word in the help for the main Rust tool, but looks like this can be difficult to achieve with docopt, so we can just skip it altogether.

Yeah that's how I felt, and another use case for not using docopt eventually!

matklad · 2017-08-24T22:19:52Z

src/bin/cargo.rs

@@ -1,3 +1,5 @@
+#![allow(non_snake_case)]


Hm, let's allow directly on flag_z fields perhaps? Alternatively, docopt uses serde now, so perhaps we can have flag_z and rename it to flag_Z on serde level?

matklad · 2017-08-24T22:22:19Z

src/cargo/core/features.rs

+//!
+//! And hopefully that's it! Bear with us though that this is, at the time of
+//! this writing, a very new feature in Cargo. If the process differs from this
+//! we'll be sure to update this documentation!


Super great comment! 💯 💯 💯 👍

matklad · 2017-08-24T22:28:55Z

src/cargo/core/features.rs

+    }
+
+    pub fn require(&self, feature: &Feature) -> CargoResult<()> {
+        if *(feature.get)(self) {


*(feature.get)(self) looks cryptic. Why do we return &bool? :)

I would try to write it like this probably:

if feature.is_enabled(self) { return Ok(()) } // bail here

matklad · 2017-08-24T22:39:08Z

src/cargo/util/toml/mod.rs

@@ -644,6 +648,9 @@ impl TomlManifest {
        };
        let profiles = build_profiles(&me.profile);
        let publish = project.publish.unwrap_or(true);
+        let empty = Vec::new();
+        let cargo_features = project.cargo_features.as_ref().unwrap_or(&empty);


Would unwrap_or(&[]) work here?

Oh that just required munging around with Option<&Vec<T>> -> Option<&[T]> which was just a pain.

matklad · 2017-08-24T22:42:54Z

tests/cargo-features.rs

+}
+
+#[test]
+fn nightly_feature_requires_nightly() {


Let's add a similar test, when a feature is activated in a dependency, and not in in the current crate. We should reject unstable dependencies for stable crates.

Ah right yeah meant to add a test for that

matklad · 2017-08-24T22:47:28Z

cc @carols10cents. I hope you'll reach consensus about crates.io side of the things :)

alexcrichton · 2017-08-25T15:59:33Z

Addressed review comments

matklad · 2017-08-25T16:01:59Z

@bors r+

bors · 2017-08-25T16:02:00Z

📌 Commit f26fc37 has been approved by matklad

bors · 2017-08-25T16:02:07Z

⌛ Testing commit f26fc37 with merge 3da1443...

Add infrastructure for nightly features and flags This PR starts adding infrastructure in Cargo for nightly features and nightly flags. The current design looks like: * There's a new `package.cargo-features` manifest key which accepts an array of strings. This array of strings is the list of enabled Cargo features for that crate. * A new suite of flags behind `-Z`, like the compiler, are accepted on the command line for all commands. * Features and unstable flags in Cargo are required to be used on Cargo's nightly channel, which is the same as Rust's nightly channel. * Features and unstable flags cannot be used on the stable/beta channels of Rust/Cargo. * Crates which enable features in their manifest are disallowed from being published to crates.io The motivation behind this support is unblock a number of efforts in Cargo by allowing them to safely get implemented behind a nightly feature gate. Once behind a feature gate they can iterate in-tree without having to worry about "insta stability" and we can also get valuable usage feedback about upstream users. Closes #4409

bors · 2017-08-25T17:10:20Z

☀️ Test successful - status-appveyor, status-travis
Approved by: matklad
Pushing 3da1443 to master...

Ericson2314 · 2017-09-03T02:27:50Z

Yay this landed!! @aturon sorry I never found time to patch in with the planning of this.

matklad · 2017-09-17T17:20:38Z

@alexcrichton I've tried to use nightly features to experiment with "optimized dependencies", but faced a problem: virtual manifests do not support cargo features, and it's not trivial to add support for them, because currently cargo-features live under [project] section, and virtual manifest lacks one.

What do you think about moving cargo-features to the top-level?

alexcrichton · 2017-09-17T17:27:40Z

@matklad seems reasonable to me!

matklad · 2017-09-17T17:29:38Z

Ok, then are we bound by some backwards compat concerns here? This shipped 24 days ago, have it hit beta?

alexcrichton · 2017-09-17T17:34:28Z

Nah nothing AFAIK is using this yet, so we can change it as we like

Add support for nightly features in Cargo

3181ef2

rust-highfive assigned matklad Aug 24, 2017

alexcrichton mentioned this pull request Aug 24, 2017

Support nightly cargo features #4409

Closed

matklad reviewed Aug 24, 2017

View reviewed changes

alexcrichton force-pushed the unstable-features branch 2 times, most recently from 7ff2fbb to 88b2f42 Compare August 25, 2017 15:58

Add infrastructure for nightly Cargo flags

f26fc37

alexcrichton force-pushed the unstable-features branch from 88b2f42 to f26fc37 Compare August 25, 2017 15:58

bors merged commit f26fc37 into rust-lang:master Aug 25, 2017

bors mentioned this pull request Aug 25, 2017

Credentials for multiple hosts. #4206

Closed

alexcrichton deleted the unstable-features branch August 25, 2017 20:16

alexcrichton mentioned this pull request Aug 25, 2017

Add --build-plan for 'cargo build' #4357

Closed

aturon mentioned this pull request Sep 1, 2017

eRFC: Cargo build system integration rust-lang/rfcs#2136

Merged

RalfJung mentioned this pull request Sep 13, 2017

Make Cargo aware of standard library dependencies rust-lang/rfcs#1133

Closed

ehuss added this to the 1.21.0 milestone Feb 6, 2022

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Add infrastructure for nightly features and flags #4433

Add infrastructure for nightly features and flags #4433

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Add infrastructure for nightly features and flags #4433

Add infrastructure for nightly features and flags #4433

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