Privatize docsrs cfg flag, use doc_cfg in CI.

.github/workflows/rust.yml

@@ -73,10 +73,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5
-      - uses: dtolnay/rust-toolchain@stable
+      - uses: dtolnay/rust-toolchain@nightly
       - run: cargo doc --locked --all-features --no-deps --document-private-items
         env:
-          RUSTDOCFLAGS: -Dwarnings
+          RUSTDOCFLAGS: -Dwarnings --cfg=instant_acme_docsrs
 
   semver:
     name: Check semver compatibility

Cargo.toml

@@ -68,7 +68,7 @@ required-features = ["hyper-rustls"]
 [package.metadata.docs.rs]
 # all non-default features except fips (cannot build on docs.rs environment)
 features = ["aws-lc-rs", "x509-parser", "time"]
-rustdoc-args = ["--cfg", "docsrs"]
+rustdoc-args = ["--cfg", "instant_acme_docsrs"]
 
 [package.metadata.cargo_check_external_types]
 allowed_external_types = [
@@ -80,3 +80,6 @@ allowed_external_types = [
     "serde::*",
     "serde_json::*",
 ]
+
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ["cfg(instant_acme_docsrs)"] }

src/lib.rs

@@ -2,7 +2,7 @@
 
 #![warn(unreachable_pub)]
 #![warn(missing_docs)]
-#![cfg_attr(docsrs, feature(doc_cfg, doc_auto_cfg))]
+#![cfg_attr(instant_acme_docsrs, feature(doc_cfg))]
 
 use std::convert::Infallible;
 use std::error::Error as StdError;