Add a warning when running cargo test -p on an optional dependency

[tomaka]

Example Cargo.toml:

[package]
name = "test"
version = "0.0.1"
authors = []

[dependencies.sub]
path = "sub"
optional = true

Running cargo test -p sub leads to package id specification "sub" matched no packages.

Removing optional = true or adding [features] default = [ "sub" ] removes the error.

[alexcrichton]

This is currently working as expected, the argument to -p is a package id specification, which is run over a certain dependency graph resolution. When you run cargo test -p sub it'll build a dependency graph for the main package, and then search for sub. This doesn't, however, include sub as its an optional feature.

[tomaka]

Oh, I need to run cargo test -p sub --features "sub"?

Now that you're saying it, that seems logical.

[alexcrichton]

Yeah, does that seem ok to you? We could possibly run the specification over the entire dependency graph if it's too painful.

[tomaka]

I think that there should at least be some kind of warning. For example searching through the list of features to see if it matches something.

[alexcrichton]

I'm fine leaving this open to track adding a warning as well (or opening a separate issue on that)

[tomaka]

Yeah, does that seem ok to you?

Actually it doesn't work, because features cannot be modified when the main package is not being built.

I get this message even when I run cargo build --feature "sub" followed by cargo test -p sub --feature "sub".
(see this travis build)

[alexcrichton]

Ah yes that's right, I forgot about that...

[stale]

As there hasn't been any activity here in a while would someone (the author, a team member, or any interested party) be able to summarise the current state, perhaps making explicit:

• Is this still relevant?
• If so, what is blocking it?
• Is it known what could be done to help move this forward?

Thank you!

(The cargo team is currently evaluating the use of Stale bot, and using #6035 as the tracking issue to gather feedback.)

If you're reading this comment from the distant future, fear not if this was closed automatically. If you believe it's still an issue please leave a comment and a team member can reopen this issue. Opening a new issue is also acceptable!

[stale]

As I didn't see any updates in 30 days I'm going to close this. Please see the previous comment for more information!