memcached extension enabled twice on PHP 7.4 and 7.3

[lukasbestle]

Describe the bug

On PHP 7.3 and 7.4, the Setup PHP action tries to install and enable the memcached extension and produces the following output:

/bin/bash /opt/hostedtoolcache/linux.sh 7.4 /home/runner/work/_actions/shivammathur/setup-php/v2/dist

==> Setup PHP
✓ PHP Switched to PHP 7.4.15

==> Setup Tools
✓ composer Added composer 2.0.11
✓ phpunit Added phpunit 9.5.2

==> Setup Extensions
✓ mbstring Enabled
✓ ctype Enabled
✓ curl Enabled
✓ gd Enabled
✓ apcu Enabled
PHP Warning:  PHP Startup: Unable to load dynamic library '/usr/lib/php/20190902/memcached.so' (tried: /usr/lib/php/20190902/memcached.so (/usr/lib/php/20190902/memcached.so: undefined symbol: igbinary_serialize), /usr/lib/php/20190902//usr/lib/php/20190902/memcached.so.so (/usr/lib/php/20190902//usr/lib/php/20190902/memcached.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
PHP Warning:  Module 'memcached' already loaded in Unknown on line 0
✓ memcached Installed and enabled
PHP Warning:  Module 'memcached' already loaded in Unknown on line 0
PHP Warning:  Module 'memcached' already loaded in Unknown on line 0
✓ pcov Enabled

==> Setup Coverage
✓ pcov.enabled=1 Added to php.ini
✓ coverage: pcov PCOV enabled as coverage driver

==> Add php.ini values
✓ apc.enabled=1 Added to php.ini
✓ apc.enable_cli=1 Added to php.ini
✓ pcov.directory=. Added to php.ini
✓ pcov.exclude='"~(vendor|tests)~"' Added to php.ini

==> Support this project
✓ setup-php https://setup-php.com/support

This results in the following error during the actual test run:

PHP Warning:  Module 'memcached' already loaded in Unknown on line 0

Version

• I have checked releases, and the bug exists in the latest patch version of v1 or v2.
• v2
• v1

Runners

• GitHub Hosted
• Self Hosted

Operating systems

ubuntu-latest (currently still 18.04.5 LTS for us)

PHP versions

7.3, 7.4, 8.0

To Reproduce

jobs:
  backend-tests:
    name: PHP ${{ matrix.php }}

    runs-on: ubuntu-latest
    strategy:
      matrix:
        php: [ "7.3", "7.4", "8.0" ]
    env:
      extensions: mbstring, ctype, curl, gd, apcu, memcached, pcov
      ini: apc.enabled=1, apc.enable_cli=1, pcov.directory=., "pcov.exclude=\"~(vendor|tests)~\""

    steps:
      - name: Setup PHP cache environment
        id: ext-cache
        uses: shivammathur/cache-extensions@v1
        with:
          php-version: ${{ matrix.php }}
          extensions: ${{ env.extensions }}
          key: php-v1

      - name: Cache PHP extensions
        uses: actions/cache@v2
        with:
          path: ${{ steps.ext-cache.outputs.dir }}
          key: ${{ steps.ext-cache.outputs.key }}
          restore-keys: ${{ steps.ext-cache.outputs.key }}

      - name: Setup PHP environment
        uses: shivammathur/setup-php@v2
        with:
          php-version: ${{ matrix.php }}
          extensions: ${{ env.extensions }}
          ini-values: ${{ env.ini }}
          coverage: pcov
          tools: phpunit:^9

Expected behavior

The memcached extension should only be enabled once.

Screenshots/Logs

You can find the full workflow output here: https://github.com/getkirby/kirby/runs/2045990826

Additional context

The same configuration works fine on PHP 8.0.

Are you willing to submit a PR?

I'm not sure where this issue is coming from TBH.

[shivammathur]

Fixed in 890ea4b and shivammathur/cache-extensions@ac51409

Test workflows:
Without cache: https://github.com/shivammathur/test-setup-php/runs/2048117303
With cache: https://github.com/shivammathur/test-setup-php/actions/runs/628232400