one_step_setup.sh

#!/usr/bin/env bash

set -e

function fail {
  # Print a newline to stderr and exit.
  echo > /dev/stderr
  exit 1
}

# Make sure we don't override an existing Pants installation.
if [ -f "pants.toml" ]; then
  echo A \`pants.toml\` file already exists in this directory. This installation script \
    needs to create a new \`pants.toml\` file. > /dev/stderr
  echo If you are trying to upgrade to a newer version of Pants, set the \`pants_version\` \
    setting in your existing \`pants.toml\` file. > /dev/stderr
  echo If you are trying to run the install process from scratch, delete the \`pants.toml\` \
    file and start again. > /dev/stderr
  fail
fi

if [ -f "pants" ]; then
  echo A file called \`pants\` already exists in this directory. This installation script \
    will overwrite this file. To proceed, either rename this file, or delete the \
    \`pants\` file. > /dev/stderr
  fail
fi

# Find the latest stable version from PyPI if not set at the command line.
if [ -z "$PANTS_VERSION" ]; then
  PANTS_VERSION=$(curl https://pypi.org/pypi/pantsbuild.pants/json |
    grep -o '"version":"[^"]*"' |
    grep -o "[0-9]*\.[0-9]*\.[0-9]*")
fi

# Create enough of a pants.toml file that our bootstrap process can run
printf '[GLOBAL]\npants_version = "%s"\n' "$PANTS_VERSION" > pants.toml

# Fetch the Pants bootstrap script and run it to verify that we fetched
# the correct version
curl -L -O https://static.pantsbuild.org/setup/pants
chmod +x ./pants
PANTS_EXEC_VERSION=$(./pants --version)

# Verify that the correct version of Pants was installed.
if [ "$PANTS_VERSION" != "$PANTS_EXEC_VERSION" ]; then
  echo Pants was installed, but the version was "$PANTS_EXEC_VERSION", not \
    "$PANTS_VERSION". > /dev/stderr
  echo Consider filing an issue at https://github.com/pantsbuild/setup/issues/new > /dev/stderr
  fail
fi

# Let the user know that everything worked
echo > /dev/stderr
echo Pants was installed successfully\! > /dev/stderr
echo > /dev/stderr