CI: rustdoc (#3613)

* CI: build rustdocs

* CI: publish rustdocs

* CI: naming

* CI: debug

* CI: MVP

* CI: copypasta

* CI: start page

* CI: better start page

* Revert "CI: debug"

This reverts commit 497051f46a0c6554b2f5978af94def74a122136a.

polkadot/.gitlab-ci.yml

@@ -41,9 +41,15 @@ default:
       - ./artifacts/
 
 .kubernetes-env:                   &kubernetes-env
+  retry:
+    max: 2
+    when:
+      - runner_system_failure
+      - unknown_failure
+      - api_failure
+  interruptible:                   true
   tags:
     - kubernetes-parity-build
-  interruptible:                   true
 
 .docker-env:                       &docker-env
   retry:
@@ -232,6 +238,28 @@ generate-impl-guide:
   script:
     - mdbook build roadmap/implementers-guide
 
+build-rustdoc:
+  stage:                           build
+  <<:                              *docker-env
+  <<:                              *rules-test
+  variables:
+    SKIP_WASM_BUILD:               1
+  artifacts:
+    name:                          "${CI_JOB_NAME}_${CI_COMMIT_REF_NAME}-doc"
+    when:                          on_success
+    expire_in:                     7 days
+    paths:
+    - ./crate-docs/
+  script:
+    # FIXME: it fails with `RUSTDOCFLAGS="-Dwarnings"` and `--all-features`
+    - time cargo doc --no-deps --workspace --verbose
+    - rm -f ./target/doc/.lock
+    - mv ./target/doc ./crate-docs
+    # FIXME: remove me after CI image gets nonroot
+    - chown -R nonroot:nonroot ./crate-docs
+    - echo "<meta http-equiv=refresh content=0;url=polkadot_service/index.html>" > ./crate-docs/index.html
+    - sccache -s
+
 .build-push-image:                 &build-push-image
   <<:                              *kubernetes-env
   image:                           quay.io/buildah/stable
@@ -393,6 +421,43 @@ publish-s3-release:                &publish-s3
     - aws s3 ls s3://${AWS_BUCKET}/${PREFIX}/${EXTRATAG}/
         --recursive --human-readable --summarize
 
+publish-rustdoc:
+  stage:                           publish
+  <<:                              *kubernetes-env
+  image:                           paritytech/tools:latest
+  variables:
+    GIT_DEPTH:                     100
+  rules:
+    - if: $CI_PIPELINE_SOURCE == "web" && $CI_COMMIT_REF_NAME == "master"
+    - if: $CI_COMMIT_REF_NAME == "master"
+  script:
+    - rm -rf /tmp/*
+    # Set git config
+    - rm -rf .git/config
+    - git config user.email "devops-team@parity.io"
+    - git config user.name "${GITHUB_USER}"
+    - git config remote.origin.url "https://${GITHUB_TOKEN}@github.com/paritytech/polkadot.git"
+    - git config remote.origin.fetch "+refs/heads/*:refs/remotes/origin/*"
+    - git fetch origin gh-pages
+    # Save README and docs
+    - cp -r ./crate-docs/ /tmp/doc/
+    - cp README.md /tmp/doc/
+    - git checkout gh-pages
+    # Remove everything and restore generated docs and README
+    - rm -rf ./*
+    - mv /tmp/doc/* .
+    # Upload files
+    - git add --all --force
+    # `git commit` has an exit code of > 0 if there is nothing to commit.
+    # This causes GitLab to exit immediately and marks this job failed.
+    # We don't want to mark the entire job failed if there's nothing to
+    # publish though, hence the `|| true`.
+    - git commit -m "Updated docs for ${CI_COMMIT_REF_NAME}" ||
+        echo "___Nothing to commit___"
+    - git push origin gh-pages --force
+  after_script:
+    - rm -rf .git/ ./*
+
 #### stage:                        deploy
 
 deploy-polkasync-kusama: