Fix docs.rs build (crate-root feature(doc_cfg)) + add docs.rs CI job

.github/workflows/ci.yml

@@ -103,3 +103,26 @@ jobs:
 
       - name: cargo doc --no-deps --all-features
         run: cargo doc --no-deps --all-features
+
+  docsrs:
+    name: Docs build (docs.rs config)
+    runs-on: ubuntu-latest
+    env:
+      # Mirror the docs.rs build environment so a docs.rs-only failure is
+      # caught here rather than only after publishing. docs.rs builds on
+      # nightly and passes `--cfg docsrs` (see [package.metadata.docs.rs] in
+      # Cargo.toml); the plain `docs` job above runs on stable without
+      # `--cfg docsrs`, so the `#[cfg_attr(docsrs, doc(cfg(...)))]` labels are
+      # inert there and a missing crate-root `feature(doc_cfg)` slips through.
+      RUSTDOCFLAGS: --cfg docsrs -D warnings -D rustdoc::broken-intra-doc-links
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Install Rust (nightly, as docs.rs uses)
+        uses: dtolnay/rust-toolchain@nightly
+
+      - name: Cache
+        uses: Swatinem/rust-cache@v2
+
+      - name: cargo doc --no-deps --all-features (docs.rs config)
+        run: cargo doc --no-deps --all-features

CHANGELOG.md

@@ -33,6 +33,16 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- **docs.rs build**: add the crate-root `#![cfg_attr(docsrs, feature(doc_cfg))]`
+  that the crate's per-module `#[cfg_attr(docsrs, doc(cfg(...)))]` labels
+  require. Without it the docs.rs build (nightly + `--cfg docsrs`) failed with
+  E0658, even though the plain stable `cargo doc` CI job — where `docsrs` is
+  unset and the attributes are inert — passed. A new CI job (`docsrs`) now
+  builds the docs the way docs.rs does (nightly + `--cfg docsrs`, warnings
+  denied) so this gap is caught before publishing.
+
+### Fixed
+
 - *(cli)* `compcol -d` no longer truncates highly-compressible large inputs.
   The streaming decode loop stopped once the compressed input was consumed,
   leaving output a block-buffering decoder (notably bzip2) still held

src/lib.rs

@@ -11,6 +11,15 @@
 
 #![no_std]
 #![forbid(unsafe_code)]
+// Enable the nightly `doc_cfg` feature when building the docs.rs doc set
+// (docs.rs passes `--cfg docsrs`). Modules across the crate carry
+// `#![cfg_attr(docsrs, doc(cfg(feature = "...")))]` to label which feature
+// each item needs; those `#[doc(cfg(...))]` attributes are experimental and
+// require this crate-level `feature(doc_cfg)`. Without it, the docs.rs build
+// (nightly + `--cfg docsrs`) fails with E0658 even though a plain stable
+// `cargo doc` — where `docsrs` is unset and the attributes are inert —
+// succeeds. Gated on `docsrs` so stable builds never see the nightly feature.
+#![cfg_attr(docsrs, feature(doc_cfg))]
 
 #[cfg(feature = "alloc")]
 extern crate alloc;