Support node-version-file input (#36)

See https://github.com/actions/setup-node/blob/v4.0.2/docs/advanced-usage.md#node-version-file

.github/workflows/ci.yml

@@ -18,3 +18,8 @@ jobs:
 
   test-default:
     uses: ./.github/workflows/test.yml
+
+  test-node-version-file:
+    uses: ./.github/workflows/test.yml
+    with:
+      node-version-file: .node-version

.github/workflows/test.yml

@@ -8,6 +8,11 @@ on:
         required: false
         default: '["18", "20", "22"]'
         type: string
+      node-version-file:
+        description: Node.js version file
+        required: false
+        default: ''
+        type: string
       os:
         description: OS name
         required: false
@@ -25,15 +30,34 @@ on:
         type: string
 
 jobs:
+  # NOTE: Prevent an empty matrix if `node-version-file` is specified
+  prepare:
+    runs-on: ubuntu-latest
+    outputs:
+      node-version: ${{ steps.init-node-version.outputs.node-version }}
+    steps:
+      - name: Initialize "node-version" parameter
+        id: init-node-version
+        run: |
+          if [[ -n "${node_version_file}" ]]; then
+            node_version='["(skipped)"]'
+          fi
+          echo "node-version=${node_version}" >> "${GITHUB_OUTPUT}"
+        env:
+          node_version: ${{ inputs.node-version }}
+          node_version_file: ${{ inputs.node-version-file }}
+
   test:
-    name: Test on Node.js ${{ matrix.node-version }} and ${{ matrix.os }}
+    needs: prepare
+
+    name: Test on Node.js ${{ inputs.node-version-file || matrix.node-version }} and ${{ matrix.os }}
 
     strategy:
       fail-fast: false
       matrix:
         # NOTE: The `strategy` property is not fully supported, so it uses `fromJson()`.
         #       For details, see https://github.saobby.my.eu.orgmunity/t/reusable-workflow-with-strategy-matrix/205676/2
-        node-version: ${{ fromJson(inputs.node-version) }}
+        node-version: ${{ fromJson(needs.prepare.outputs.node-version) }}
         os: ${{ fromJson(inputs.os) }}
         exclude: ${{ fromJson(inputs.exclude) }}
 
@@ -49,19 +73,40 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Set up Node.js ${{ matrix.node-version }}
+        if: ${{ !inputs.node-version-file }}
+        id: setup-node
         uses: actions/setup-node@v4
         with:
           node-version: ${{ matrix.node-version }}
           cache: npm
 
+      - name: Set up Node.js from ${{ inputs.node-version-file }} file
+        if: ${{ inputs.node-version-file }}
+        id: setup-node-file
+        uses: actions/setup-node@v4
+        with:
+          node-version-file: ${{ inputs.node-version-file }}
+          cache: npm
+
+      - name: Detect Node.js version
+        id: node-version
+        shell: bash
+        run: echo "value=${node_version}" >> "${GITHUB_OUTPUT}"
+        env:
+          node_version: ${{ steps.setup-node-file.outputs.node-version || steps.setup-node.outputs.node-version }}
+
       # NOTE: npm v10 has dropped support for Node.js v16.
       - name: Install npm v9
-        if: ${{ startsWith(matrix.node-version, '16') }}
-        run: npm install --global npm@9 && npm --version
+        if: ${{ startsWith(steps.node-version.outputs.value, 'v16') }}
+        run: |
+          npm install --global npm@9
+          echo "npm: $(npm --version)"
 
       - name: Install latest npm
-        if: ${{ !startsWith(matrix.node-version, '16') }}
-        run: npm install --global npm@latest && npm --version
+        if: ${{ !startsWith(steps.node-version.outputs.value, 'v16') }}
+        run: |
+          npm install --global npm@latest
+          echo "npm: $(npm --version)"
 
       - name: Install dependencies
         run: npm ci

.node-version

@@ -0,0 +1 @@
+20