docs.rs build crashes (not because of semantic error)

[jost-s]

We've been publishing crates successfully for a while. Since a recent release a month ago, docs.rs fails at building the documentation. The error is not a semantic error:

[INFO] [stderr] thread 'rustc' panicked at 'no entry found for key', src/librustdoc/passes/collect_intra_doc_links.rs:929:16
[INFO] [stderr] note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
[INFO] [stderr] 
[INFO] [stderr] error: internal compiler error: unexpected panic
[INFO] [stderr] 
[INFO] [stderr] error: Unrecognized option: 'extern-html-root-url'

Full error log

Building the docs locally with cargo doc succeeds. Building the docs locally with the nightly Rust installation produces an error, although a different one:

$ nix-shell --arg rustVersion '{ track = "nightly"; version = "2022-01-20"; }' --pure --run "unset RUSTFLAGS; cargo rustdoc --lib --manifest-path=crates/holochain/Cargo.toml -- -Z unstable-options --check --cap-lints warn --disable-per-crate-search"
(...)
warning: unresolved link to `run_callback`
   --> crates/holochain/src/core/ribosome.rs:555:5
    |
555 | /     /// Helper function for running a validation callback. Just calls
556 | |     /// [`run_callback`][] under the hood.
557 | |     /// [`run_callback`]: #method.run_callback
    | |______________________________________________^
    |
    = note: the link appears in this line:

            [`run_callback`][] under the hood.
             ^^^^^^^^^^^^^^
    = note: no item named `run_callback` in scope
    = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`

warning: `holochain` (lib doc) generated 27 warnings
    Finished dev [unoptimized + debuginfo] target(s) in 9.84s

Please help debugging the failing docs.rs build.

[Nemo157]

You're hitting the issues in #1632, if you try nightly-2022-01-27 or later you should see it locally also. Once the upstream bug is fixed in a new nightly we can queue a rebuild of the docs.

[Nemo157]

To simplify issue management I'm going to merge this in to #1632 to track the issues all together.