Scraping examples: works locally but not on docs.rs

[killercup]

In bevyengine/bevy#9154, I tried adding metadata to have the many examples bevy comes with show up in their API docs.

I have a full reproduction and detailed description of what I tried here: killercup/test-rustdoc-example-scraping-across-workspace-on-docrs#1

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This relates to rust-lang/rust#88791

cc @rust-lang/docs-rs

(talked to @GuillaumeGomez about this already)

[killercup]

After talking to some folks from @rust-lang/docs-rs, we discovered that no scraped examples are shown for items that are re-exported from other crates. It works for path dependencies.

[GuillaumeGomez]

This now needs to be moved to cargo as it seems to be a cargo issue from what we could uncover.

[fmease]

Have you tried minimizing this issue to not rely on Cargo but just on rustc & rustdoc and have failed? Just from reading the issue description, this sounds like a https://github.com/rust-lang/rust/labels/A-cross-crate-reexports issue but I haven't looked much into this issue.

[GuillaumeGomez]

It works if the crate is specified with path but doesn't when the crate is downloaded from crates.io (the default). That's why we reached this conclusion.

[GuillaumeGomez]

Moved the issue in docs.rs as it seems to be a docs.rs-specific issue: every crate gets its scraped examples working when documenting them locally. My guess is that maybe we are using a read-only FS when we should not. To be confirmed.

[syphar]

@GuillaumeGomez from what I remember of the discussion with @killercup , we were able to reproduce this locally, perhaps @Nemo157 knows more?

[GuillaumeGomez]

That's also what I remember and yet I can't reproduce it locally again. @killercup and I talked about it in killercup/test-rustdoc-example-scraping-across-workspace-on-docrs#1. The surprising part being that the docs.rs command line (with cargo rustdoc) works locally.

[Nemo157]

Yeah, my recollection is that the difference was that it didn't reproduce in the repository, but only in the published package, not anything to do with what docs.rs does with that package specifically.

[GuillaumeGomez]

Ok, I'll keep the issue here for the time being and try to check what's going on when we get the crate from crates.io.

[GuillaumeGomez]

So more information about this (for bevy): when adding back the workspace members:

[workspace]
members = [
  "crates/*",
]

And copying the relevant files locally, the examples are scraped as expected. Next step is to take a look into cargo and figure out why it's even needed in the first place.

[GuillaumeGomez]

Fixed in rust-lang/cargo#13074.