Add PR preview deployments

.github/workflows/preview_build.yml

@@ -0,0 +1,52 @@
+# This action builds and deploys egui_demo_app on each pull request created
+# Security notes:
+# The preview deployment is split in two workflows, preview_build and preview_deploy.
+# `preview_build` runs on pull_request, so it won't have any access to the repositories secrets, so it is safe to
+# build / execute untrusted code.
+# `preview_deploy` has access to the repositories secrets (so it can push to the pr preview repo) but won't run
+# any untrusted code (it will just extract the build artifact and push it to the pages branch where it will
+# automatically be deployed).
+
+name: Preview Build
+
+on:
+  - pull_request
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - run: rustup toolchain install stable --profile minimal --target wasm32-unknown-unknown
+      - uses: Swatinem/rust-cache@v2
+        with:
+          prefix-key: "pr-preview-"
+
+      - name: "Install wasmopt / binaryen"
+        run: |
+          sudo apt-get update && sudo apt-get install binaryen
+
+      - run: |
+          scripts/build_demo_web.sh --release
+
+      - name: Remove gitignore file
+        # We need to remove the .gitignore, otherwise the deploy via git will not include the js and wasm files
+        run: |
+          rm -rf web_demo/.gitignore
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: web_demo
+          path: web_demo
+
+      - name: Generate meta.json
+        env:
+          PR_NUMBER: ${{ github.event.number }}
+          PR_BRANCH: ${{ github.head_ref }}
+        run: |
+          echo "{\"pr_number\": \"$PR_NUMBER\", \"pr_branch\": \"$PR_BRANCH\"}" > meta.json
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: meta.json
+          path: meta.json

.github/workflows/preview_cleanup.yml

@@ -0,0 +1,31 @@
+name: Preview Cleanup
+
+permissions:
+  contents: write
+
+on:
+  pull_request_target:
+    types:
+      - closed
+
+jobs:
+  cleanup:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+      - run: mkdir -p empty_dir
+      - name: Url slug variable
+        run: |
+          echo "URL_SLUG=${{ github.event.pull_request.number }}-${{ github.event.pull_request.head.ref }}" >> $GITHUB_ENV
+      - name: Deploy
+        uses: JamesIves/github-pages-deploy-action@v4
+        with:
+          folder: empty_dir
+          repository-name: egui-pr-preview/pr
+          branch: 'main'
+          clean: true
+          target-folder: ${{ env.URL_SLUG }}
+          ssh-key: ${{ secrets.DEPLOY_KEY }}
+          commit-message: "Remove preview for PR ${{ env.URL_SLUG }}"
+          single-commit: true

.github/workflows/preview_deploy.yml

@@ -0,0 +1,68 @@
+name: Preview Deploy
+
+permissions:
+  contents: write
+  pull-requests: write
+
+on:
+  workflow_run:
+    workflows:
+      - "Preview Build"
+    types:
+      - completed
+
+# Since we use single_commit and force on the deploy action, only one deploy action can run at a time.
+# Should this create a bottleneck we might have to set single_commit and force to false which should allow
+# for the deployments to run in parallel.
+concurrency:
+  group: preview_deploy
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+      - name: 'Download build artifact'
+        uses: actions/download-artifact@v4
+        with:
+          name: web_demo
+          path: web_demo_artifact
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          run-id: ${{ github.event.workflow_run.id }}
+      - name: 'Download build meta'
+        uses: actions/download-artifact@v4
+        with:
+          name: meta.json
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          run-id: ${{ github.event.workflow_run.id }}
+
+      - name: Parse meta.json
+        run: |
+          echo "PR_NUMBER=$(jq -r .pr_number meta.json)" >> $GITHUB_ENV
+          echo "PR_BRANCH=$(jq -r .pr_branch meta.json)" >> $GITHUB_ENV
+
+      - name: Url slug variable
+        run: |
+          echo "URL_SLUG=${{ env.PR_NUMBER }}-${{ env.PR_BRANCH }}" >> $GITHUB_ENV
+
+      - name: Deploy
+        uses: JamesIves/github-pages-deploy-action@v4
+        with:
+          folder: web_demo_artifact
+          repository-name: egui-pr-preview/pr
+          branch: 'main'
+          clean: true
+          target-folder: ${{ env.URL_SLUG }}
+          ssh-key: ${{ secrets.DEPLOY_KEY }}
+          commit-message: "Update preview for PR ${{ env.URL_SLUG }}"
+          single-commit: true
+
+      - name: Comment PR
+        uses: thollander/actions-comment-pull-request@v2
+        with:
+          message: |
+            Preview available at https://egui-pr-preview.github.io/pr/${{ env.URL_SLUG }}
+            Note that it might take a couple seconds for the update to show up after the preview_build workflow has completed.
+          pr_number: ${{ env.PR_NUMBER }}
+          comment_tag: 'egui-preview'

web_demo/index.html

@@ -119,7 +119,7 @@
     </script>
 
     <!-- this is the JS generated by the `wasm-bindgen` CLI tool -->
-    <script src="egui_demo_app.js"></script>
+    <script src="./egui_demo_app.js"></script>
 
     <script>
         // We'll defer our execution until the wasm is ready to go.