published futures-core 0.3.1 fails doctest due to stripped path dependency

[kentfredric]

Operating as a Linux Vendor, its desirable for many, many reasons to be able to execute tests on published crates. ( For instance, when publishing a new rust version as a vendor, being able to re-execute all the tests for everything currently packaged to identify new compile errors, or functional regressions, helps make sure that all vendorized crates will be error-free at the time of user consumption )

But anything relying on path dependencies pretty much screws this.

See also:

• futures-channel tests do not work out of the tree #1017
• futures-executor tests do not work out of the tree #1020
• futures-util tests do not work out of the tree #1019

Which are all closed, and sill relevant, but I can't actually re-open a bug.

The filer of those bugs does appear to be potentially a fedora rep, confirming that multiple vendors have this as a complaint.

Though our obligation is really only to make sure you know there's an issue, and know we're applying nasty hacks to get around it, and all such hacks are always better to be fixed upstream ( In part because it means a given vendor freshly trying to package this doesn't have to stumble upon the problem and DIY their own hack around it, and ensures closer vendor tracking of crates vs upstream )

As a side note: A dozen or so crates having the same repository and the same bug tracker seems very sub-optimal, because its hard to directly map crate patches to git patches and vice-versa, and hard to find issues pertaining to a specific crate when there are a dozen crates using the same issue tracker, which github seems very sub-optimal for.

    Finished test [unoptimized + debuginfo] target(s) in 0.01s
     Running target/debug/deps/futures_core-a2b3d337c4676fee

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

   Doc-tests futures_core

running 2 tests
test src/task/__internal/atomic_waker.rs - task::__internal::atomic_waker::AtomicWaker (line 38) ... FAILED
test src/task/__internal/atomic_waker.rs - task::__internal::atomic_waker::AtomicWaker::register (line 233) ... FAILED

failures:

---- src/task/__internal/atomic_waker.rs - task::__internal::atomic_waker::AtomicWaker (line 38) stdout ----
error[E0433]: failed to resolve: use of undeclared type or module `futures`
 --> src/task/__internal/atomic_waker.rs:39:5
  |
4 | use futures::future::Future;
  |     ^^^^^^^ use of undeclared type or module `futures`

error[E0433]: failed to resolve: use of undeclared type or module `futures`
 --> src/task/__internal/atomic_waker.rs:40:5
  |
5 | use futures::task::{Context, Poll, AtomicWaker};
  |     ^^^^^^^ use of undeclared type or module `futures`

error[E0433]: failed to resolve: use of undeclared type or module `AtomicWaker`
  --> src/task/__internal/atomic_waker.rs:57:20
   |
22 |             waker: AtomicWaker::new(),
   |                    ^^^^^^^^^^^ use of undeclared type or module `AtomicWaker`

error[E0433]: failed to resolve: use of undeclared type or module `Poll`
  --> src/task/__internal/atomic_waker.rs:74:20
   |
39 |             return Poll::Ready(());
   |                    ^^^^ use of undeclared type or module `Poll`

error[E0433]: failed to resolve: use of undeclared type or module `Poll`
  --> src/task/__internal/atomic_waker.rs:82:13
   |
47 |             Poll::Ready(())
   |             ^^^^ use of undeclared type or module `Poll`

error[E0433]: failed to resolve: use of undeclared type or module `Poll`
  --> src/task/__internal/atomic_waker.rs:84:13
   |
49 |             Poll::Pending
   |             ^^^^ use of undeclared type or module `Poll`

error[E0412]: cannot find type `AtomicWaker` in this scope
  --> src/task/__internal/atomic_waker.rs:47:12
   |
12 |     waker: AtomicWaker,
   |            ^^^^^^^^^^^ not found in this scope
   |
help: possible candidate is found in another module, you can import it into scope
   |
3  | use futures_core::task::__internal::AtomicWaker;
   |

error[E0405]: cannot find trait `Future` in this scope
  --> src/task/__internal/atomic_waker.rs:68:6
   |
33 | impl Future for Flag {
   |      ^^^^^^ not found in this scope
   |
help: possible candidates are found in other modules, you can import them into scope
   |
3  | use core::future::Future;
   |
3  | use futures_core::Future;
   |
3  | use futures_core::core_reexport::future::Future;
   |
3  | use futures_core::future::Future;
   |
     and 1 other candidate

error[E0412]: cannot find type `Context` in this scope
  --> src/task/__internal/atomic_waker.rs:71:44
   |
36 |     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {
   |                                            ^^^^^^^ not found in this scope
   |
help: possible candidates are found in other modules, you can import them into scope
   |
3  | use core::task::Context;
   |
3  | use futures_core::core_reexport::task::Context;
   |
3  | use futures_core::task::Context;
   |
3  | use std::task::Context;
   |

error[E0412]: cannot find type `Poll` in this scope
  --> src/task/__internal/atomic_waker.rs:71:60
   |
36 |     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {
   |                                                            ^^^^ not found in this scope
   |
help: possible candidates are found in other modules, you can import them into scope
   |
3  | use core::task::Poll;
   |
3  | use futures_core::core_reexport::task::Poll;
   |
3  | use futures_core::task::Poll;
   |
3  | use std::task::Poll;
   |

error: aborting due to 10 previous errors

Some errors have detailed explanations: E0405, E0412, E0433.
For more information about an error, try `rustc --explain E0405`.
Couldn't compile the test.
---- src/task/__internal/atomic_waker.rs - task::__internal::atomic_waker::AtomicWaker::register (line 233) stdout ----
error[E0433]: failed to resolve: use of undeclared type or module `futures`
 --> src/task/__internal/atomic_waker.rs:234:5
  |
4 | use futures::future::Future;
  |     ^^^^^^^ use of undeclared type or module `futures`

error[E0433]: failed to resolve: use of undeclared type or module `futures`
 --> src/task/__internal/atomic_waker.rs:235:5
  |
5 | use futures::task::{Context, Poll, AtomicWaker};
  |     ^^^^^^^ use of undeclared type or module `futures`

error[E0433]: failed to resolve: use of undeclared type or module `Poll`
  --> src/task/__internal/atomic_waker.rs:254:13
   |
24 |             Poll::Ready(())
   |             ^^^^ use of undeclared type or module `Poll`

error[E0433]: failed to resolve: use of undeclared type or module `Poll`
  --> src/task/__internal/atomic_waker.rs:256:13
   |
26 |             Poll::Pending
   |             ^^^^ use of undeclared type or module `Poll`

error[E0412]: cannot find type `AtomicWaker` in this scope
  --> src/task/__internal/atomic_waker.rs:241:12
   |
11 |     waker: AtomicWaker,
   |            ^^^^^^^^^^^ not found in this scope
   |
help: possible candidate is found in another module, you can import it into scope
   |
3  | use futures_core::task::__internal::AtomicWaker;
   |

error[E0405]: cannot find trait `Future` in this scope
  --> src/task/__internal/atomic_waker.rs:245:6
   |
15 | impl Future for Flag {
   |      ^^^^^^ not found in this scope
   |
help: possible candidates are found in other modules, you can import them into scope
   |
3  | use core::future::Future;
   |
3  | use futures_core::Future;
   |
3  | use futures_core::core_reexport::future::Future;
   |
3  | use futures_core::future::Future;
   |
     and 1 other candidate

error[E0412]: cannot find type `Context` in this scope
  --> src/task/__internal/atomic_waker.rs:248:44
   |
18 |     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {
   |                                            ^^^^^^^ not found in this scope
   |
help: possible candidates are found in other modules, you can import them into scope
   |
3  | use core::task::Context;
   |
3  | use futures_core::core_reexport::task::Context;
   |
3  | use futures_core::task::Context;
   |
3  | use std::task::Context;
   |

error[E0412]: cannot find type `Poll` in this scope
  --> src/task/__internal/atomic_waker.rs:248:60
   |
18 |     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {
   |                                                            ^^^^ not found in this scope
   |
help: possible candidates are found in other modules, you can import them into scope
   |
3  | use core::task::Poll;
   |
3  | use futures_core::core_reexport::task::Poll;
   |
3  | use futures_core::task::Poll;
   |
3  | use std::task::Poll;
   |

error: aborting due to 8 previous errors

Some errors have detailed explanations: E0405, E0412, E0433.
For more information about an error, try `rustc --explain E0405`.
Couldn't compile the test.

failures:
    src/task/__internal/atomic_waker.rs - task::__internal::atomic_waker::AtomicWaker (line 38)
    src/task/__internal/atomic_waker.rs - task::__internal::atomic_waker::AtomicWaker::register (line 233)

test result: FAILED. 0 passed; 2 failed; 0 ignored; 0 measured; 0 filtered out

error: test failed, to rerun pass '--doc'

[Nemo157]

The reason this is stripped is because it is impossible to publish crates with circular dev-dependencies, see rust-lang/cargo#4242. It’s not really a path dependency, if cargo were enhanced to allow whole-workspace publishes, or allowed unresolveable dev-dependencies temporarily, then this would end up referring to the published version of futures and work.

[kentfredric]

One respectable work-around is simply not having test cases which necessitate extra dependencies.

Quite a few other "futures" crates seem to have no problems due to this, though they're made work I think by the tests being entirely stripped.

Its just inline and doc tests that prove to be a bit harder to exorcise.

But the desirable result is that ultimately, cargo test not failing due to not running any tests, is generally better than cargo test failing due to some aspect of publishing not being shored up.

But ideally some tests exist, even if they're not necessarily comprehensive.

Another "ok" workaround is gating out tests, either by default, or on demand based on a '#![cfg( ... )]" attribute.

But the over-arching pattern here is "if something can't compile and run, it probably shouldn't be shipped like that", though there's a multitude of different ways of achieving that goal based on different needs.

[alexanderkjall]

I'm trying to package version 0.3.1 for debian, and I also ran into this problem.

[cramertj]

Unfortunately, as @Nemo157 said above, this isn't fixable by us today without additional changes to cargo to allow for uploading packages with unresolved dev dependencies.

[taiki-e]

Closing -- This isn't fixable on our side. Once fixed on the cargo side, we can revisit.

(FWIW, there is a discussion in users.rust-lang.org about testing on crate uploaded to crates.io.)