🚦 Extract and cache code-coverge results

The code-coverage step on CI is currently one of the longest stalls on
the system, largely due to the fact that it needs to re-run tests, which
does require some level of recompilation between steps.

Since this is something that should not change if the source input
or dependencies has not changed, this adds new caching that will cache
the last generated code-coverage result and pull it back up whenever
it is needed.

.github/actions/cargo-code-coverage/action.yaml

@@ -0,0 +1,57 @@
+name: cargo-code-coverage
+description: "An action for generating code-coverage for a project using cargo-llvm-cov"
+
+inputs:
+  output-file:
+    required: true
+    description: "The output file to write the coverage information to, which gets cached."
+  minimum-requirement:
+    required: false
+    description: "A decimal value indicating the minimum required coverage requirements. 0 disables this."
+    default: "0.0"
+
+runs:
+  using: "composite"
+  steps:
+    - name: Cache Coverage
+      id: cargo-coverage
+      uses: actions/cache@v3
+      with:
+        path: ${{ inputs.output-file }}
+        key: cargo-coverage-${{ runner.os }}-${{ hashFiles('**/*.rs', '**/Cargo.toml', 'Cargo.toml') }}
+
+    - name: Install cargo-llvm-cov
+      if: steps.cargo-coverage.outputs.cache-hit != 'true'
+      uses: taiki-e/install-action@cargo-llvm-cov
+
+    - name: Generate Coverage Coverage
+      if: steps.cargo-coverage.outputs.cache-hit != 'true'
+      shell: bash
+      run: cargo llvm-cov --json --output-path ${{ inputs.output-file }}
+
+    - name: Emit 'coverage' output
+      id: report
+      shell: bash
+      run: echo "coverage=$(cat ${{ inputs.output-file }})" >> "${GITHUB_OUTPUT}"
+
+    - name: Check Coverage Requirement
+      if: inputs.minimum-requirement > 0.0
+      shell: bash
+      run: |
+        coverage=${{fromJson(steps.report.outputs.coverage).data[0].totals.lines.percent}}
+
+        if [[ ${{inputs.minimum-requirement}} > ${coverage} ]]; then
+          echo                                                                 \
+            "::error::Project code coverage fell below minimum desired '${{inputs.minimum-requirement}}%'!" \
+            "The current coverage is '${COVERAGE}%.'"                          \
+            "Please either add more tests, or lower the requirements."
+          exit 1
+        fi
+
+    - name: Upload Coverage Artifact
+      uses: actions/upload-artifact@v1
+      if: steps.report.outcome == 'success'
+      continue-on-error: true
+      with:
+        name: ${{ runner.os }}-codecov
+        path: ${{ inputs.output-file }}

.github/workflows/build.yaml

@@ -158,9 +158,6 @@ jobs:
     defaults:
       run:
         shell: bash
-    env:
-      OUTPUT_FILE: ${{ matrix.os }}-codecov.json
-      COVERAGE_MINIMUM: ${{ 0.0 }}
 
     steps:
       - name: Checkout
@@ -174,9 +171,6 @@ jobs:
         with:
           components: llvm-tools-preview
 
-      - name: Install cargo-llvm-cov
-        uses: taiki-e/install-action@cargo-llvm-cov
-
       - name: Build
         id: build
         uses: ./.github/actions/cargo-build
@@ -185,28 +179,8 @@ jobs:
         id: test
         run: cargo test --verbose
 
-      - name: Generate Coverage Report
-        id: report
-        run: |
-          cargo llvm-cov --json --output-path ${{ env.OUTPUT_FILE }}
-          echo "coverage=$(cat ${{ env.OUTPUT_FILE }})" >> "${GITHUB_OUTPUT}"
-
-      - name: Check Coverage Requirement
-        if: env.COVERAGE_MINIMUM > 0.0
-        env:
-          COVERAGE: ${{fromJson(steps.report.outputs.coverage).data[0].totals.lines.percent}}
-        run: |
-          if [[ ${{env.COVERAGE_MINIMUM}} > ${{env.COVERAGE}} ]]; then
-            echo "Error: Project code coverage fell below minimum desired '${COVERAGE_MINIMUM}%'!" >&2
-            echo "The current coverage is '${COVERAGE}%.'" >&2
-            echo "Please either add more tests, or lower the requirements." >&2
-            exit 1
-          fi
-
-      - name: Upload Coverage Artifact
-        uses: actions/upload-artifact@v1
-        if: steps.report.outcome == 'success'
-        continue-on-error: true
+      - name: Coverage
+        uses: ./.github/actions/cargo-code-coverage
         with:
-          name: ${{matrix.os}}-codecov
-          path: ${{env.OUTPUT_FILE}}
+          output-file: ${{ matrix.os }}-codecov.json
+          minimum-required: 0.0