ci: code coverage report

.github/actions-rs/grcov.yml

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+output-type: lcov
+output-path: ./lcov.info

.github/workflows/generate_coverage_pr.yaml

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+name: Generate Coverage Report (PR)
+
+on:
+  push:
+    branches:
+      - develop  
+  pull_request:
+    branches:
+      - develop
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  coverage:
+    name: Generate Coverage Report
+    environment: coverage
+    runs-on: ubuntu-latest
+    env:
+      CARGO_INCREMENTAL: "0"
+      RUSTFLAGS: "-Cinstrument-coverage"
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install LLVM tools
+        run: sudo apt-get update && sudo apt-get install -y llvm
+
+      - id: setup
+        name: Setup Toolchain
+        uses: dtolnay/rust-toolchain@nightly
+        with:
+          toolchain: nightly
+          components: llvm-tools-preview
+
+      - id: cache
+        name: Enable Workflow Cache
+        uses: Swatinem/rust-cache@v2
+
+      - id: tools
+        name: Install Tools
+        uses: taiki-e/install-action@v2
+        with:
+          tool: grcov,cargo-llvm-cov
+
+      - id: build_and_test
+        name: Build and test
+        run: |
+          echo "${{ secrets.CODECOV_TOKEN }}"
+          cargo clean 
+          cargo build 
+          cargo test -- --nocapture
+
+      - id: coverage
+        name: Generate Coverage Report
+        run: |
+          cargo llvm-cov --lcov --output-path=./lcov.info
+
+      - name: Store PR number and commit SHA
+        run: |
+          echo "Storing PR number ${{ github.event.number }}"
+          echo "${{ github.event.number }}" > pr_number.txt
+
+          echo "Storing commit SHA ${{ github.event.pull_request.head.sha }}"
+          echo "${{ github.event.pull_request.head.sha }}" > commit_sha.txt
+
+      # Workaround for https://github.com/orgs/community/discussions/25220
+      # Triggered sub-workflow is not able to detect the original commit/PR which is available
+      # in this workflow.
+      - name: Store PR number
+        uses: actions/upload-artifact@v4
+        with:
+          name: pr_number
+          path: pr_number.txt
+
+      - name: Store commit SHA
+        uses: actions/upload-artifact@v4
+        with:
+          name: commit_sha
+          path: commit_sha.txt
+
+      # This stores the coverage report in artifacts. The actual upload to Codecov
+      # is executed by a different workflow `coverage-report.yml`. The reason for this
+      # split is because `on.pull_request` workflows don't have access to secrets.
+      - name: Store coverage report in artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: codecov_report
+          path: ./lcov.info
+
+      - run: |
+          echo "The coverage report was stored in Github artifacts."
+          echo "It will be uploaded to Codecov using [coverage-report.yml] workflow shortly."

.github/workflows/upload_coverage_pr.yaml

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+name: Upload Coverage Report (PR)
+
+on:
+  # This workflow is triggered after every successfull execution
+  # of `Generate Coverage Report` workflow.
+  workflow_run:
+    workflows: ["Generate Coverage Report (PR)"]
+    types:
+      - completed
+
+permissions:
+  actions: write
+  contents: write
+  issues: write
+  pull-requests: write
+
+jobs:
+  coverage:
+    name: Upload Coverage Report
+    environment: coverage
+    runs-on: ubuntu-latest
+    steps:
+      - name: "Download existing coverage report"
+        id: prepare_report
+        uses: actions/github-script@v7
+        with:
+          script: |
+            var fs = require('fs');
+
+            // List artifacts of the workflow run that triggered this workflow
+            var artifacts = await github.rest.actions.listWorkflowRunArtifacts({
+               owner: context.repo.owner,
+               repo: context.repo.repo,
+               run_id: context.payload.workflow_run.id,
+            });
+
+            let codecovReport = artifacts.data.artifacts.filter((artifact) => {
+              return artifact.name == "codecov_report";
+            });
+
+            if (codecovReport.length != 1) {
+              throw new Error("Unexpected number of {codecov_report} artifacts: " + codecovReport.length);
+            }
+
+            var download = await github.rest.actions.downloadArtifact({
+               owner: context.repo.owner,
+               repo: context.repo.repo,
+               artifact_id: codecovReport[0].id,
+               archive_format: 'zip',
+            });
+            fs.writeFileSync('codecov_report.zip', Buffer.from(download.data));
+
+            let prNumber = artifacts.data.artifacts.filter((artifact) => {
+              return artifact.name == "pr_number";
+            });
+
+            if (prNumber.length != 1) {
+              throw new Error("Unexpected number of {pr_number} artifacts: " + prNumber.length);
+            }
+
+            var download = await github.rest.actions.downloadArtifact({
+               owner: context.repo.owner,
+               repo: context.repo.repo,
+               artifact_id: prNumber[0].id,
+               archive_format: 'zip',
+            });
+            fs.writeFileSync('pr_number.zip', Buffer.from(download.data));
+
+            let commitSha = artifacts.data.artifacts.filter((artifact) => {
+              return artifact.name == "commit_sha";
+            });
+
+            if (commitSha.length != 1) {
+              throw new Error("Unexpected number of {commit_sha} artifacts: " + commitSha.length);
+            }
+
+            var download = await github.rest.actions.downloadArtifact({
+               owner: context.repo.owner,
+               repo: context.repo.repo,
+               artifact_id: commitSha[0].id,
+               archive_format: 'zip',
+            });
+            fs.writeFileSync('commit_sha.zip', Buffer.from(download.data));
+
+      - id: parse_previous_artifacts
+        run: |
+          unzip codecov_report.zip
+          unzip pr_number.zip
+          unzip commit_sha.zip
+
+          echo "Detected PR is: $(<pr_number.txt)"
+          echo "Detected commit_sha is: $(<commit_sha.txt)"
+
+          # Make the params available as step output
+          echo "override_pr=$(<pr_number.txt)" >> "$GITHUB_OUTPUT"
+          echo "override_commit=$(<commit_sha.txt)" >> "$GITHUB_OUTPUT"
+
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ steps.parse_previous_artifacts.outputs.override_commit || '' }}
+          path: repo_root
+
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v4
+        with:
+          verbose: true
+          token: ${{ secrets.CODECOV_TOKEN }}
+          files: ${{ github.workspace }}/lcov.info
+          fail_ci_if_error: true
+          # Manual overrides for these parameters are needed because automatic detection
+          # in codecov-action does not work for non-`pull_request` workflows.
+          # In `main` branch push, these default to empty strings since we want to run
+          # the analysis on HEAD.
+          override_commit: ${{ steps.parse_previous_artifacts.outputs.override_commit || '' }}
+          override_pr: ${{ steps.parse_previous_artifacts.outputs.override_pr || '' }}
+          working-directory: ${{ github.workspace }}/repo_root
+          # Location where coverage report files are searched for
+          directory: ${{ github.workspace }}