Use a raw cfg flag for the unstable doc_cfg feature

Author: weiznich

.github/workflows/ci.yml

@@ -47,7 +47,8 @@ jobs:
         shell: bash
         if: matrix.rust == 'nightly'
         run: |
-          echo "RUSTFLAGS=--cap-lints=warn" >> $GITHUB_ENV
+          echo "RUSTFLAGS=--cap-lints=warn --cfg doc_cfg" >> $GITHUB_ENV
+          echo "RUSTDOCFLAGS=--cfg doc_cfg" >> $GITHUB_ENV
 
       - name: Install postgres (Linux)
         if: runner.os == 'Linux' && matrix.backend == 'postgres'
@@ -299,7 +300,7 @@ jobs:
         uses: actions-rs/cargo@v1
         with:
           command: doc
-          args: --manifest-path diesel/Cargo.toml --no-deps --no-default-features --features "${{ matrix.backend }} unstable doc_cfg i-implement-a-third-party-backend-and-opt-into-breaking-changes"
+          args: --manifest-path diesel/Cargo.toml --no-deps --no-default-features --features "${{ matrix.backend }} unstable i-implement-a-third-party-backend-and-opt-into-breaking-changes"
 
       - name: Run rustdoc
         if: matrix.run != 'nightly'

.github/workflows/doc.yml

@@ -37,8 +37,11 @@ jobs:
         sudo apt-get update
         sudo apt-get -y install libmysqlclient-dev libsqlite3-dev libpq-dev
     - name: Build documentation
+      env:
+        RUSTFLAGS: "--cfg doc_cfg"
+        RUSTDOCFLAGS: "--cfg doc_cfg"
       run:
-        cargo +nightly doc --manifest-path diesel/Cargo.toml --features "postgres sqlite mysql extras i-implement-a-third-party-backend-and-opt-into-breaking-changes doc_cfg" --workspace
+        cargo +nightly doc --manifest-path diesel/Cargo.toml --features "postgres sqlite mysql extras i-implement-a-third-party-backend-and-opt-into-breaking-changes" --workspace
 
     - name: Publish documentation
       if: success()

diesel/Cargo.toml

@@ -68,3 +68,5 @@ doc_cfg = []
 [package.metadata.docs.rs]
 features = ["postgres", "mysql", "sqlite", "extras"]
 no-default-features = true
+rustc-args = ["--cfg", "doc_cfg"]
+rustdoc-args = ["--cfg", "doc_cfg"]

diesel/src/lib.rs

@@ -158,7 +158,7 @@
 //! - `32-column-tables`
 
 #![cfg_attr(feature = "unstable", feature(trait_alias))]
-#![cfg_attr(feature = "doc_cfg", feature(doc_cfg, doc_auto_cfg))]
+#![cfg_attr(doc_cfg, feature(doc_cfg, doc_auto_cfg))]
 #![cfg_attr(feature = "128-column-tables", recursion_limit = "256")]
 // Built-in Lints
 #![deny(warnings)]