An example script for running happo in CI

happo-ci.bash

#!/usr/local/bin/dock bash

# Generates and uploads Happo diffs for the differences between the previous
# and current commit.
set -euo pipefail

PREVIOUS_SHA="$(git rev-parse ${1-HEAD^})"
CURRENT_SHA="$(git rev-parse ${1-HEAD})"
echo "Previous SHA: ${PREVIOUS_SHA}"
echo "Current SHA: ${CURRENT_SHA}"

yarn install

run-happo() {
  sha=$1
  git checkout --quiet $sha

  yarn install
  
  # Here's a good place to drop in build steps for dependencies of the run. 

  yarn run happo run $sha
}

# Check if we need to generate a baseline
if ! yarn run happo has-report $PREVIOUS_SHA; then
  echo "No previous report found for ${PREVIOUS_SHA}. Generating one..."
  run-happo $PREVIOUS_SHA
fi

run-happo $CURRENT_SHA

# Finally, post a comment with a link to diffs
summary=$(npm run --silent happo compare $PREVIOUS_SHA $CURRENT_SHA || true)

if [ -n "$summary" ]; then
  # Post a comment to the Gerrit patch set linking to the diff(s)
  # (Use two newlines to make comment look good in the Gerrit web UI)
  message="Message from Happo:

  $summary"
  echo $message

  # https://gerrit-review.googlesource.com/Documentation/cmd-review.html
  ssh -p <redacted> <redacted>@<redacted> \
    gerrit review \'--message="$message"\' $GERRIT_PATCHSET_REVISION
fi