GitHub Actions

# .github/workflows/build-size.yml

name: BuildSize

on:
  pull_request:
    branches:
      - main

jobs:
  build:
    runs-on: ubuntu-latest
    permissions:
      pull-requests: write
    steps:
      - name: Checkout code
        uses: actions/checkout@v3

        # Start of custom build steps for the project
      - name: Setup Node.js environment
        uses: actions/setup-node@v3
        with:
          node-version-file: .nvmrc

      - name: Install dependencies
        run: npm install

      - name: Build project
        run: npm run build
        # End of custom build steps for the project

      - name: List files
        run: ls -la

      - name: Set build size
        run: |
          SIZE=$(du -sh $folder | grep -o -E "[0-9]+(\.)?[0-9]*(M|K)")
          echo "::set-output name=size::$SIZE"
        id: build-size
        shell: bash
        # Set the name of the folder whose size should be commented
        env:
          folder: '.next'

      - name: Echo build size
        run: echo "size is ${{ steps.build-size.outputs.size }}"

      - name: Make comment
        uses: thollander/actions-comment-pull-request@v1.3.0
        with:
          message: 'Build size is: ${{ steps.build-size.outputs.size }}'
          comment_includes: 'size'
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

Usage

Update the steps in the above action to build the project. The above example builds an npm project but it would be needed to swap the steps to build non-npm projects

Update the name of the folder/file whose size should be included in the PR. Requires updating the folder in the name: Set build size step

And that should be it. You should now see the the PR commenting the size of the folder/file you wanted to be included.