WordPress latest tag does not parse environment variables correctly

[thijsvanloef]

Hello, while testing with the new latest WordPress (5.8) I noticed the environment variables not being parsed correctly resulting in a Error establishing a database connection error.

Steps to Reproduce

1. Pull the wordpress:latest image
2. Create a docker-compose.yml file based on the official documentation
3. Change the environment variables from the WordPress service

version: '3.1'

services:

  wordpress:
    image: wordpress:latest
    restart: always
    ports:
      - 8080:80
    environment:
      WORDPRESS_DB_HOST: THIS_SHOULD_APPEAR
      WORDPRESS_DB_USER: THIS_SHOULD_APPEAR
      WORDPRESS_DB_PASSWORD: THIS_SHOULD_APPEAR
      WORDPRESS_DB_NAME: THIS_SHOULD_APPEAR
    volumes:
      - wordpress:/var/www/html

  db:
    image: mysql:5.7
    restart: always
    environment:
      MYSQL_DATABASE: THIS_SHOULD_APPEAR
      MYSQL_USER: THIS_SHOULD_APPEAR
      MYSQL_PASSWORD: THIS_SHOULD_APPEAR
      MYSQL_RANDOM_ROOT_PASSWORD: '1'
    volumes:
      - db:/var/lib/mysql

volumes:
  wordpress:
  db:

4. Startup the docker-compose with docker-compose up -d
5. Enter the wordpress container with docker exec -it wordpress_container bash
6. Look inside the wp-config.php file: cat wp-config.php

Expected Result

**/ ** MySQL settings - You can get this info from your web host ** //
/** The name of the database for WordPress */
define( 'DB_NAME', getenv_docker('WORDPRESS_DB_NAME', 'THIS_SHOULD_APPEAR') );

/** MySQL database username */
define( 'DB_USER', getenv_docker('WORDPRESS_DB_USER', 'THIS_SHOULD_APPEAR') );

/** MySQL database password */
define( 'DB_PASSWORD', getenv_docker('WORDPRESS_DB_PASSWORD', 'THIS_SHOULD_APPEAR') );

/**
 * Docker image fallback values above are sourced from the official WordPress installation wizard:
 * https://github.com/WordPress/WordPress/blob/f9cc35ebad82753e9c86de322ea5c76a9001c7e2/wp-admin/setup-config.php#L216-L230
 * (However, using "example username" and "example password" in your database is strongly discouraged.  Please use strong, random credentials!)
 */

/** MySQL hostname */
define( 'DB_HOST', getenv_docker('WORDPRESS_DB_HOST', 'THIS_SHOULD_APPEAR') );

/** Database charset to use in creating database tables. */
define( 'DB_CHARSET', getenv_docker('WORDPRESS_DB_CHARSET', 'utf8') );

/** The database collate type. Don't change this if in doubt. */
define( 'DB_COLLATE', getenv_docker('WORDPRESS_DB_COLLATE', '') );
**

Actual Result

**/ ** MySQL settings - You can get this info from your web host ** //
/** The name of the database for WordPress */
define( 'DB_NAME', getenv_docker('WORDPRESS_DB_NAME', 'wordpress') );

/** MySQL database username */
define( 'DB_USER', getenv_docker('WORDPRESS_DB_USER', 'example username') );

/** MySQL database password */
define( 'DB_PASSWORD', getenv_docker('WORDPRESS_DB_PASSWORD', 'example password') );

/**
 * Docker image fallback values above are sourced from the official WordPress installation wizard:
 * https://github.com/WordPress/WordPress/blob/f9cc35ebad82753e9c86de322ea5c76a9001c7e2/wp-admin/setup-config.php#L216-L230
 * (However, using "example username" and "example password" in your database is strongly discouraged.  Please use strong, random credentials!)
 */

/** MySQL hostname */
define( 'DB_HOST', getenv_docker('WORDPRESS_DB_HOST', 'mysql') );

/** Database charset to use in creating database tables. */
define( 'DB_CHARSET', getenv_docker('WORDPRESS_DB_CHARSET', 'utf8') );

/** The database collate type. Don't change this if in doubt. */
define( 'DB_COLLATE', getenv_docker('WORDPRESS_DB_COLLATE', '') );
**

[yosifkit]

The values are no longer edited into the wp-config.php, but are instead just read from the environment directly (the getenv_docker function). This functionality was added to the beta/rc releases in #557 and migrated to the main releases in #572.

(I just tried the play-with-docker which uses the example stack.yml and it works just fine. https://github.com/docker-library/docs/blob/5b2c8b4507ed1aa2f7259b9d9f45f9f4eea115ef/wordpress/README.md#-via-docker-stack-deploy-or-docker-compose)

A random guess, but for your compose file, if you set WORDPRESS_DB_HOST to anything but db it will not work (i.e. the DNS name of the mysql container).