CI: add beta channel lint workflow

Add a new CI workflow to check compilation and linting with the Rust
beta channel. This helps catch issues early before they appear in
stable releases.

Changes:
- Add rust.beta version to versions.yaml
- Update load-versions action to expose RUST_BETA_VERSION
- Create lint-beta.yaml workflow that runs check-beta and lint-beta
- Add check-beta and lint-beta make targets that use cargo +beta
- Job uses continue-on-error to allow failures without blocking PRs
- Workflow runs on push to main/develop, PRs, and weekly on Mondays

The make targets explicitly use cargo +beta to override rust-toolchain.toml.
The workflow is configured to run weekly to catch regressions in beta
before they land in stable, and on PRs to provide early warning of
compatibility issues.

Author: iostat

.github/actions/load-versions/action.yml

@@ -5,6 +5,9 @@ outputs:
   rust-stable:
     description: "Rust stable version"
     value: ${{ steps.load.outputs.rust-stable }}
+  rust-beta:
+    description: "Rust beta version"
+    value: ${{ steps.load.outputs.rust-beta }}
   rust-nightly:
     description: "Rust nightly version"
     value: ${{ steps.load.outputs.rust-nightly }}
@@ -26,6 +29,7 @@ runs:
 
         # Read versions from YAML file using yq
         RUST_STABLE=$(yq eval '.rust.stable' "$VERSIONS_FILE")
+        RUST_BETA=$(yq eval '.rust.beta' "$VERSIONS_FILE")
         RUST_NIGHTLY=$(yq eval '.rust.nightly' "$VERSIONS_FILE")
         OCAML_VERSION=$(yq eval '.ocaml.version' "$VERSIONS_FILE")
         NODE_VERSION_YAML=$(yq eval '.node.version' "$VERSIONS_FILE")
@@ -43,18 +47,21 @@ runs:
 
         # Set outputs
         echo "rust-stable=$RUST_STABLE" >> $GITHUB_OUTPUT
+        echo "rust-beta=$RUST_BETA" >> $GITHUB_OUTPUT
         echo "rust-nightly=$RUST_NIGHTLY" >> $GITHUB_OUTPUT
         echo "ocaml-version=$OCAML_VERSION" >> $GITHUB_OUTPUT
         echo "node-version=$NODE_VERSION_YAML" >> $GITHUB_OUTPUT
 
         # Also set as environment variables for convenience
         echo "RUST_STABLE_VERSION=$RUST_STABLE" >> $GITHUB_ENV
+        echo "RUST_BETA_VERSION=$RUST_BETA" >> $GITHUB_ENV
         echo "RUST_NIGHTLY_VERSION=$RUST_NIGHTLY" >> $GITHUB_ENV
         echo "OCAML_VERSION=$OCAML_VERSION" >> $GITHUB_ENV
         echo "NODE_VERSION=$NODE_VERSION_YAML" >> $GITHUB_ENV
 
         echo "Loaded versions:"
         echo "  Rust stable: $RUST_STABLE"
+        echo "  Rust beta: $RUST_BETA"
         echo "  Rust nightly: $RUST_NIGHTLY"
         echo "  OCaml: $OCAML_VERSION"
         echo "  Node.js: $NODE_VERSION_YAML"

.github/config/versions.yaml

@@ -11,6 +11,7 @@
 
 rust:
   stable: "1.84"
+  beta: "beta"
   nightly: "nightly"
 
 ocaml:

.github/workflows/lint-beta.yaml

@@ -0,0 +1,47 @@
+name: Lint (Beta Channel)
+
+on:
+  push:
+    branches: [ main, develop ]
+  pull_request:
+  schedule:
+    # Run weekly on Mondays at 00:00 UTC
+    - cron: '0 0 * * 1'
+
+jobs:
+  lint-beta:
+    timeout-minutes: 15
+    name: Lint (Beta) - ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    # Allow this job to fail without failing the entire workflow
+    continue-on-error: true
+    strategy:
+      matrix:
+        os: [ubuntu-24.04]
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Load versions
+        uses: ./.github/actions/load-versions
+
+      - name: Setup build dependencies
+        uses: ./.github/actions/setup-build-deps
+
+      - name: Use shared OCaml setting up steps
+        uses: ./.github/actions/setup-ocaml
+        with:
+          ocaml_version: ${{ env.OCAML_VERSION }}
+
+      - name: Setup Rust (Beta)
+        uses: ./.github/actions/setup-rust
+        with:
+          toolchain: ${{ env.RUST_BETA_VERSION }}
+          components: clippy, rustfmt
+          cache-prefix: lint-beta-${{ env.RUST_BETA_VERSION }}-v0
+
+      - name: Run make check-beta
+        run: make check-beta
+
+      - name: Run make lint-beta
+        run: make lint-beta
+

Makefile

@@ -151,6 +151,10 @@ bench-database: ## Run ledger database benchmark
 check: ## Check code for compilation errors
 	cargo check --all-targets
 
+.PHONY: check-beta
+check-beta: ## Check code for compilation errors using beta Rust
+	cargo +beta check --all-targets
+
 .PHONY: check-tx-fuzzing
 check-tx-fuzzing: ## Check the transaction fuzzing tools, requires nightly Rust
 	@cd tools/fuzzing && cargo +$(NIGHTLY_RUST_VERSION) check
@@ -244,6 +248,10 @@ format-md: ## Format all markdown and MDX files to wrap at 80 characters
 lint: ## Run linter (clippy)
 	cargo clippy --all-targets -- -D warnings --allow clippy::mutable_key_type
 
+.PHONY: lint-beta
+lint-beta: ## Run linter (clippy) using beta Rust
+	cargo +beta clippy --all-targets -- -D warnings --allow clippy::mutable_key_type
+
 .PHONY: lint-bash
 lint-bash: ## Check all shell scripts using shellcheck
 	@echo "Running shellcheck on shell scripts..."