ci: unused dependencies sanity check (#590)

* ci: add unused deps sanity check

* ci: fix unused deps issue template title

* ci: rename udeps job

* chore: formatting

* chore: make `cargo-udeps` ignore `aquamarine`

* deps: resolve unused deps

* ci: check every feature and target in udeps job

.github/SANITY_UNUSED_DEPS_ISSUE_TEMPLATE.md

@@ -0,0 +1,15 @@
+---
+title: "chore: some installed deps are not needed"
+labels: C-debt, A-dependencies
+---
+
+Some dependencies specified in `Cargo.toml` are not needed.
+
+Check the [unused dependencies sanity check]({{env.WORKFLOW_URL}}) workflow for details.
+
+This issue was raised by the workflow at `.github/workflows/sanity.yml`.
+
+> **Note**
+> If this is a false positive, please refer to the [`cargo-udeps` docs][cargo-udeps-docs] on how to ignore the dependencies.
+
+[cargo-udeps-docs]: https://github.com/est31/cargo-udeps#ignoring-some-of-the-dependencies

.github/workflows/sanity.yml

@@ -43,8 +43,6 @@ jobs:
 
       - name: Install latest nextest release
         uses: taiki-e/install-action@nextest
-      - name: Install cargo-llvm-cov
-        uses: taiki-e/install-action@cargo-llvm-cov
 
       - name: Update packages
         run: cargo update
@@ -60,3 +58,30 @@ jobs:
         with:
           update_existing: true
           filename: .github/SANITY_DEPS_ISSUE_TEMPLATE.md
+
+  unused-deps:
+    # Pin to `20.04` instead of `ubuntu-latest`, until ubuntu-latest migration is complete
+    # See also <https://github.com/foundry-rs/foundry/issues/3827>
+    runs-on: ubuntu-20.04
+    name: unused dependencies
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v3
+      - name: Install toolchain
+        uses: dtolnay/rust-toolchain@nightly
+
+      - name: Install cargo-udeps
+        run: cargo install cargo-udeps --locked
+
+      - name: Check for unused dependencies
+        run: cargo +nightly udeps --all-features --all-targets
+
+      - uses: JasonEtco/create-an-issue@v2
+        if: ${{ failure() }}
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          WORKFLOW_URL: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
+        with:
+          update_existing: true
+          filename: .github/SANITY_UNUSED_DEPS_ISSUE_TEMPLATE.md
+