Performance: Run weekly audits against Sourcegraph.com (#26779)

.github/workflows/lighthouse-production.yml

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+name: Lighthouse production audit
+on:
+  workflow_dispatch:
+  schedule:
+  # Every Monday at 12pm UTC
+  - cron: '0 12 * * MON'
+
+jobs:
+  update:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+
+    # set up correct version of node
+    - id: nvmrc
+      run: echo ::set-output name=NODE_VERSION::$(cat .nvmrc)
+    - uses: actions/setup-node@v2
+      with: { node-version: '${{ steps.nvmrc.outputs.NODE_VERSION }}' }
+
+    - name: Install dependencies
+      run: yarn --ignore-engines --ignore-scripts
+
+    - name: Run Lighthouse
+      run: |
+        echo -e "*Weekly audit against Sourcegraph.com*\n" > lighthouse_results.txt
+        ./dev/ci/generate-lighthouse-slack-report.sh ":house: *Homepage*" "https://sourcegraph.com/search" ./lighthouse_results.txt
+        ./dev/ci/generate-lighthouse-slack-report.sh ":mag_right: *Search results*" "https://sourcegraph.com/search?q=repo:sourcegraph/lighthouse-ci-test-repository+file:index.js" ./lighthouse_results.txt
+        ./dev/ci/generate-lighthouse-slack-report.sh ":repository: *Repository page*" "https://sourcegraph.com/github.com/sourcegraph/lighthouse-ci-test-repository" ./lighthouse_results.txt
+        ./dev/ci/generate-lighthouse-slack-report.sh ":code: *File blob*" "https://sourcegraph.com/github.com/sourcegraph/lighthouse-ci-test-repository/-/blob/index.js" ./lighthouse_results.txt
+        curl -X POST -H 'Content-type: application/json' --data "{'text':'$(cat ./lighthouse_results.txt)'}" ${{ secrets.LIGHTHOUSE_SLACK_WEBHOOK }}

dev/ci/generate-lighthouse-slack-report.sh

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+#!/usr/bin/env bash
+
+# This script will run Lighthouse audits against a specified URL
+# and generate a text report suitable for uploading to Slack.
+
+# Friendly name to associate with the Lighthouse audit
+NAME=$1
+# URL to run Lighthouse against
+URL=$2
+# File to output results to
+OUTPUT_FILE=$3
+
+yarn lhci collect --url="$URL" --no-lighthouserc --settings.preset="desktop" --numberOfRuns=10
+
+# LHCI doesn't an provide a way to easily expose the temporary storage URL, we have to extract it ourselves
+REPORT_URL=$(yarn lhci upload --target=temporary-public-storage | grep -o "https:\/\/storage.googleapis.*.html\+")
+# Primary result source, we'll use this to extract the raw audit data.
+yarn lhci upload --target=filesystem
+
+# Lighthouse runs multiple times and takes the median to account for varying network latency
+REPRESENTATIVE_RUN=$(jq -r '.[] | select(.isRepresentativeRun==true)' manifest.json)
+
+# Extract the Lighthouse score for each relevant category
+PERFORMANCE=$(jq -r '.summary.performance' <<<"$REPRESENTATIVE_RUN")
+ACCESSIBILITY=$(jq -r '.summary.accessibility' <<<"$REPRESENTATIVE_RUN")
+BEST_PRACTICES=$(jq -r '.summary."best-practices"' <<<"$REPRESENTATIVE_RUN")
+SEO=$(jq -r '.summary.seo' <<<"$REPRESENTATIVE_RUN")
+
+SUMMARY="
+$NAME: <$REPORT_URL|Report>
+Performance: $PERFORMANCE/1
+Accessibility: $ACCESSIBILITY/1
+Best practices: $BEST_PRACTICES/1
+SEO: $SEO/1\n
+"
+
+echo -e "$SUMMARY" >>"$OUTPUT_FILE"