Add code coverage to CI with Coveralls integration (payjoin#385)

This brings the github actions up-to-date with latest versions and adds
more descriptive names to the workflow steps.

It also swaps the ordering of `rust-cache` and the rust toolchain
installation steps so that cache actually works.

Finally, a new CI step adds code coverage measurements using
`cargo-llvm` and uploads the results to Coveralls.

Author: spacebear21

.github/workflows/rust.yml

@@ -1,10 +1,9 @@
-name: Test and Build
+name: Continuous integration
 
 on: [push, pull_request]
 
 jobs:
-
-  test:
+  Test:
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
@@ -13,43 +12,62 @@ jobs:
           - 1.63.0 # MSRV
           - stable
           - nightly
-
     steps:
-      - uses: actions/checkout@v2
-      - uses: Swatinem/rust-cache@v1.2.0
-      - uses: actions-rs/toolchain@v1
+      - name: "Checkout repo"
+        uses: actions/checkout@v4
+      - name: "Install ${{ matrix.rust }} toolchain"
+        # https://github.com/dtolnay/rust-toolchain?tab=readme-ov-file#inputs
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ matrix.rust }}
-          override: true
+      - name: "Use cache"
+        uses: Swatinem/rust-cache@v2
       - name: Run tests
         run: RUST_LOG=debug bash contrib/test.sh
 
-  rustfmt:
+  Format:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: Swatinem/rust-cache@v1.2.0
-      - uses: actions-rs/toolchain@v1
-        with:
-          toolchain: nightly
-          override: true
+      - name: "Checkout repo"
+        uses: actions/checkout@v4
+      - name: "Install nightly toolchain"
+        uses: dtolnay/rust-toolchain@nightly
+      - name: "Use cache"
+        uses: Swatinem/rust-cache@v2
       - run: rustup component add rustfmt --toolchain nightly-x86_64-unknown-linux-gnu
-      - name: fmt check
+      - name: "Run formatting check"
         run: cargo fmt --all -- --check
 
-  clippy:
+  Lint:
     runs-on: ubuntu-latest
     steps:
       - name: "Checkout repo"
         uses: actions/checkout@v4
-      - name: "Use caching"
-        uses: Swatinem/rust-cache@v1.2.0
       - name: "Install nightly toolchain"
-        uses: actions-rs/toolchain@v1
-        with:
-          toolchain: nightly
-          override: true
+        uses: dtolnay/rust-toolchain@nightly
+      - name: "Use cache"
+        uses: Swatinem/rust-cache@v2
       - name: "Install clippy"
         run: rustup component add clippy --toolchain nightly-x86_64-unknown-linux-gnu
       - name: "Run linting"
         run: bash contrib/lint.sh
+
+  Coverage:
+    name: Code coverage
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+    steps:
+      - name: "Checkout repo"
+        uses: actions/checkout@v4
+      - name: "Install toolchain"
+        # https://github.com/dtolnay/rust-toolchain
+        uses: dtolnay/rust-toolchain@stable
+      - name: "Use cache"
+        uses: Swatinem/rust-cache@v2
+      - name: "Install cargo-llvm-cov"
+        uses: taiki-e/install-action@cargo-llvm-cov
+      - name: "Generate code coverage for tests"
+        run: bash contrib/coverage.sh
+      - name: "Upload report to coveralls"
+        uses: coverallsapp/github-action@v2

README.md

@@ -72,7 +72,7 @@ Seeking review of the code that verifies there is no overpayment. Contributions
 - [x] CI
 - [x] Integration tests
 - [ ] Fuzzing
-- [ ] Coverage measurement
+- [x] Coverage measurement
 
 ## Minimum Supported Rust Version (MSRV)
 

contrib/coverage.sh

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+set -e
+
+# https://github.com/taiki-e/cargo-llvm-cov?tab=readme-ov-file#merge-coverages-generated-under-different-test-conditions
+cargo llvm-cov clean --workspace # remove artifacts that may affect the coverage results
+cargo llvm-cov --no-report --features=send,receive
+cargo llvm-cov --no-report --features=v2,danger-local-https,io
+cargo llvm-cov report --lcov --output-path lcov.info # generate report without tests