Panic in cargo::version

[dtolnay]

Using the newest nightly cargo. I can't get the version because --version panics. Rustup installed it along with rustc 1.17.0-nightly (e4eb964dd 2017-03-11).

$ RUST_BACKTRACE=1 cargo --version
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', /checkout/src/libcore/option.rs:323
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: cargo::version
             at /checkout/src/libcore/macros.rs:21
             at /checkout/cargo/src/cargo/lib.rs:263
   1: cargo::execute
             at /checkout/cargo/src/bin/cargo.rs:156
   2: cargo::call_main_without_stdin
             at /checkout/cargo/src/cargo/lib.rs:128
   3: cargo::main
             at /checkout/cargo/src/bin/cargo.rs:91
             at /checkout/cargo/src/bin/cargo.rs:84

It affects other commands as well:

$ RUST_BACKTRACE=1 cargo update
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', /checkout/src/libcore/option.rs:323
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: cargo::version
             at /checkout/src/libcore/macros.rs:21
             at /checkout/cargo/src/cargo/lib.rs:263
   1: cargo::ops::registry::http_handle
             at /checkout/cargo/src/cargo/ops/registry.rs:227
   2: <cargo::sources::registry::remote::RemoteRegistry<'cfg> as cargo::sources::registry::RegistryData>::update_index
             at /checkout/cargo/src/cargo/sources/registry/remote.rs:63
   3: cargo::sources::registry::RegistrySource::do_update
             at /checkout/cargo/src/cargo/sources/registry/mod.rs:309
   4: <cargo::sources::registry::RegistrySource<'cfg> as cargo::core::source::Source>::update
             at /checkout/cargo/src/cargo/sources/registry/mod.rs:353
   5: cargo::core::registry::PackageRegistry::ensure_loaded
             at /checkout/cargo/src/cargo/core/registry.rs:191
             at /checkout/cargo/src/cargo/util/errors.rs:58
             at /checkout/cargo/src/cargo/core/registry.rs:180
             at /checkout/cargo/src/cargo/core/registry.rs:141
   6: <cargo::core::registry::PackageRegistry<'cfg> as cargo::core::registry::Registry>::query
             at /checkout/cargo/src/cargo/core/registry.rs:339
   7: <&'a mut I as core::iter::iterator::Iterator>::next
             at /checkout/cargo/src/cargo/core/resolver/mod.rs:859
             at /checkout/cargo/src/cargo/core/resolver/mod.rs:832
             at /checkout/src/libcore/ops.rs:2654
             at /checkout/src/libcore/option.rs:383
             at /checkout/src/libcore/iter/mod.rs:999
             at /checkout/src/libcore/result.rs:1087
             at /checkout/src/libcore/iter/iterator.rs:2197
   8: cargo::core::resolver::activate
             at /checkout/src/libcollections/vec.rs:1649
             at /checkout/src/libcollections/vec.rs:1562
             at /checkout/src/libcore/result.rs:1104
             at /checkout/src/libcore/iter/iterator.rs:1221
             at /checkout/cargo/src/cargo/core/resolver/mod.rs:831
             at /checkout/cargo/src/cargo/core/resolver/mod.rs:340
   9: cargo::core::resolver::activate_deps_loop
             at /checkout/cargo/src/cargo/core/resolver/mod.rs:457
  10: cargo::core::resolver::resolve
             at /checkout/cargo/src/cargo/core/resolver/mod.rs:280
  11: cargo::ops::resolve::resolve_with_previous
             at /checkout/cargo/src/cargo/ops/resolve.rs:225
  12: cargo::ops::cargo_generate_lockfile::update_lockfile
             at /checkout/cargo/src/cargo/ops/cargo_generate_lockfile.rs:77
  13: cargo::try_execute_builtin_command
             at /checkout/cargo/src/bin/update.rs:77
             at /checkout/cargo/src/cargo/lib.rs:128
             at /checkout/cargo/src/bin/cargo.rs:259
  14: cargo::execute
             at /checkout/cargo/src/bin/cargo.rs:223
  15: cargo::call_main_without_stdin
             at /checkout/cargo/src/cargo/lib.rs:128
  16: cargo::main
             at /checkout/cargo/src/bin/cargo.rs:91
             at /checkout/cargo/src/bin/cargo.rs:84

[alexcrichton]

I've started fixing this in #3820, next step is to land the submodule update in rust-lang/rust

[alexcrichton]

PR against rust-lang/rust: rust-lang/rust#40450

[ruuda]

This bug has quite some impact, because Travis CI runs cargo --version and cargo build/test --verbose by default, so all builds that use the nightly channel were broken. While #3820 fixes the cause in this case, that is no guarantee that things aren’t going to break in the future. Would it be possible to add a dry-run check to the test suite? Something as simple as the shell script below, which should exit with a 0 exit code, would have caught this, right?

set -e
cargo --version
cargo new foo
cd $_
cargo build --verbose
cargo test --verbose

[alexcrichton]

@ruuda we in fact have these tests and run them in rust-lang/rust. We just don't run the test suite for the right Cargo, and that's tracked by rust-lang/rust#38531.

Just trying to point out that we're not trying to be negligent here, the interactions are all very tricky.