Disable wgpu-core documentation as a workaround for #4905.

This enables `cargo doc` to succeed in a reasonable amount of time,
as long as the reader isn't looking for documentation for `wgpu-core`
itself.

CHANGELOG.md

@@ -44,6 +44,7 @@ Bottom level categories:
 #### General
 
 - Fix profiling with `tracy`. By @waywardmonkeys in [#5988](https://github.com/gfx-rs/wgpu/pull/5988)
+- As a workaround for [issue #4905](https://github.com/gfx-rs/wgpu/issues/4905), `wgpu-core` is undocumented unless `--cfg wgpu_core_doc` feature is enabled. By @kpreid in [#5987](https://github.com/gfx-rs/wgpu/pull/5987)
 
 ## 22.0.0 (2024-07-17)
 

wgpu-core/src/lib.rs

@@ -2,6 +2,20 @@
 //! It is designed for integration into browsers, as well as wrapping
 //! into other language-specific user-friendly libraries.
 //!
+#![cfg_attr(
+    not(any(not(doc), wgpu_core_doc)),
+    doc = r#"\
+## Documentation hidden
+
+As a workaround for [an issue in rustdoc](https://github.com/rust-lang/rust/issues/114891)
+that [affects `wgpu-core` documentation builds \
+severely](https://github.com/gfx-rs/wgpu/issues/4905),
+the documentation for `wgpu-core` is empty unless built with
+`RUSTFLAGS="--cfg wgpu_core_doc"`, which may take a very long time.
+"#
+)]
+#![cfg(any(not(doc), wgpu_core_doc))]
+//!
 //! ## Feature flags
 #![doc = document_features::document_features!()]
 //!