The locally-installed docs try to load non-local assets, causing them to fail on a bad connection.

[umanwizard]

The locally-installed docs that open when you use rustup docs try to load a few assets from a CDN. This is fine if you have no network connection at all, because they will fail quickly and the page will render.

However, if you have a very poor/slow network connection, they will try to load, and nothing on the page will render.

Please make the locally-installed docs not depend on non-local resources at all.

[jsha]

I checked over the rustup-installed docs using the command below, and found that the std / rustdoc docs don't appear to have this problem, but the book loads its logo and favicon from an Internet URL. Also the Clippy book appears to use mdBook's MathJax support, which is inserting <script async type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML">. Note: the async there may have been added since 2018 when this issue was filed, and probably alleviates the performance problem on a slow connection.

$ cd ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu && rg 'src=.https?://|<link[^>]*href=.https?://' -l | sort          share/doc/rust/html/book/associated-types.html
share/doc/rust/html/book/attributes.html
share/doc/rust/html/book/bibliography.html
share/doc/rust/html/book/borrow-and-asref.html
share/doc/rust/html/book/casting-between-types.html
share/doc/rust/html/book/choosing-your-guarantees.html
share/doc/rust/html/book/closures.html
share/doc/rust/html/book/comments.html
share/doc/rust/html/book/compiler-plugins.html
share/doc/rust/html/book/concurrency.html
share/doc/rust/html/book/conditional-compilation.html
share/doc/rust/html/book/const-and-static.html
share/doc/rust/html/book/crates-and-modules.html
share/doc/rust/html/book/deref-coercions.html
share/doc/rust/html/book/documentation.html
share/doc/rust/html/book/drop.html
share/doc/rust/html/book/effective-rust.html
share/doc/rust/html/book/enums.html
share/doc/rust/html/book/error-handling.html
share/doc/rust/html/book/ffi.html
share/doc/rust/html/book/functions.html
share/doc/rust/html/book/generics.html
share/doc/rust/html/book/getting-started.html
share/doc/rust/html/book/glossary.html
share/doc/rust/html/book/guessing-game.html
share/doc/rust/html/book/if.html
share/doc/rust/html/book/if-let.html
share/doc/rust/html/book/iterators.html
share/doc/rust/html/book/lifetimes.html
share/doc/rust/html/book/loops.html
share/doc/rust/html/book/macros.html
share/doc/rust/html/book/match.html
share/doc/rust/html/book/method-syntax.html
share/doc/rust/html/book/mutability.html
share/doc/rust/html/book/operators-and-overloading.html
share/doc/rust/html/book/ownership.html
share/doc/rust/html/book/patterns.html
share/doc/rust/html/book/primitive-types.html
share/doc/rust/html/book/procedural-macros.html
share/doc/rust/html/book/raw-pointers.html
share/doc/rust/html/book/README.html
share/doc/rust/html/book/references-and-borrowing.html
share/doc/rust/html/book/release-channels.html
share/doc/rust/html/book/strings.html
share/doc/rust/html/book/structs.html
share/doc/rust/html/book/SUMMARY.html
share/doc/rust/html/book/syntax-and-semantics.html
share/doc/rust/html/book/syntax-index.html
share/doc/rust/html/book/testing.html
share/doc/rust/html/book/the-stack-and-the-heap.html
share/doc/rust/html/book/trait-objects.html
share/doc/rust/html/book/traits.html
share/doc/rust/html/book/type-aliases.html
share/doc/rust/html/book/ufcs.html
share/doc/rust/html/book/unsafe.html
share/doc/rust/html/book/unsized-types.html
share/doc/rust/html/book/using-rust-without-the-standard-library.html
share/doc/rust/html/book/variable-bindings.html
share/doc/rust/html/book/vectors.html
share/doc/rust/html/clippy/configuration.html
share/doc/rust/html/clippy/continuous_integration/github_actions.html
share/doc/rust/html/clippy/continuous_integration/index.html
share/doc/rust/html/clippy/continuous_integration/travis.html
share/doc/rust/html/clippy/development/adding_lints.html
share/doc/rust/html/clippy/development/basics.html
share/doc/rust/html/clippy/development/common_tools_writing_lints.html
share/doc/rust/html/clippy/development/index.html
share/doc/rust/html/clippy/development/infrastructure/backport.html
share/doc/rust/html/clippy/development/infrastructure/book.html
share/doc/rust/html/clippy/development/infrastructure/changelog_update.html
share/doc/rust/html/clippy/development/infrastructure/index.html
share/doc/rust/html/clippy/development/infrastructure/release.html
share/doc/rust/html/clippy/development/infrastructure/sync.html
share/doc/rust/html/clippy/development/proposals/index.html
share/doc/rust/html/clippy/development/proposals/roadmap-2021.html
share/doc/rust/html/clippy/index.html
share/doc/rust/html/clippy/installation.html
share/doc/rust/html/clippy/lints.html
share/doc/rust/html/clippy/print.html
share/doc/rust/html/clippy/usage.html
share/doc/rust/html/complement-design-faq.html
share/doc/rust/html/complement-lang-faq.html
share/doc/rust/html/complement-project-faq.html
share/doc/rust/html/edition-guide/print.html
share/doc/rust/html/edition-guide/rust-2018/new-keywords.html
share/doc/rust/html/edition-guide/rust-2018/path-changes.html
share/doc/rust/html/edition-guide/rust-2018/trait-fn-parameters.html
share/doc/rust/html/grammar.html
share/doc/rust/html/guide-crates.html
share/doc/rust/html/guide-error-handling.html
share/doc/rust/html/guide-ffi.html
share/doc/rust/html/guide.html
share/doc/rust/html/guide-macros.html
share/doc/rust/html/guide-ownership.html
share/doc/rust/html/guide-plugins.html
share/doc/rust/html/guide-pointers.html
share/doc/rust/html/guide-strings.html
share/doc/rust/html/guide-tasks.html
share/doc/rust/html/guide-testing.html
share/doc/rust/html/guide-unsafe.html
share/doc/rust/html/intro.html
share/doc/rust/html/not_found.html
share/doc/rust/html/reference.html
share/doc/rust/html/rustdoc.html
share/doc/rust/html/rust.html
share/doc/rust/html/tutorial.html
share/doc/rust/html/version_info.html