feat(db): add robust support for WP_CLI_MYSQLDUMP override with fallback handling

[manhphuc]

This PR improves the SQL dump binary resolution logic used by wp db export.

What this change does

• Adds safe, explicit support for overriding the dump client via the WP_CLI_MYSQLDUMP environment variable.
• Correctly handles both:
  • absolute executable paths
  • plain command names resolved through PATH
• Ignores invalid or non-executable absolute paths to avoid breaking wp db export.
• Falls back reliably to the appropriate default:
  • mariadb-dump on MariaDB installs
  • mysqldump otherwise

Why this is useful

Many Docker-based or custom server environments provide only one of the dump clients, or store it in a non-standard location. This update makes wp db export more predictable and easier to configure across those setups.

Testing

The change was tested in multiple scenarios:

1. Valid absolute override
   WP_CLI_MYSQLDUMP=/usr/bin/mysqldump → export succeeds, correct binary selected.

2. Invalid absolute override
   Non-existent file → ignored, fallback selected correctly.

3. No environment override
   MariaDB installation correctly defaults to mariadb-dump.

All scenarios produced valid export files and correct debug messages.

---

Happy to adjust anything if needed. Thanks for reviewing!

[gemini-code-assist[bot]]

Summary of Changes

Hello @manhphuc, I'm Gemini Code Assist[^1]! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the wp db export command's ability to locate and utilize the correct SQL dump binary. By introducing support for the WP_CLI_MYSQLDUMP environment variable, it provides users with greater control and flexibility in specifying their preferred dump client. The changes ensure robust handling of various path types, intelligent error recovery for invalid overrides, and reliable fallbacks, making the wp db export functionality more adaptable and predictable across diverse server environments, especially those with non-standard dump client configurations.

Highlights

• Environment Variable Override: Introduces explicit support for overriding the SQL dump client via the WP_CLI_MYSQLDUMP environment variable, allowing users to specify a custom binary.
• Robust Path Handling: The system now correctly handles both absolute executable paths and plain command names (resolved through PATH), providing flexibility in how the dump client is specified.
• Intelligent Fallback: Invalid or non-executable absolute paths provided via the environment variable are gracefully ignored, and the system reliably falls back to mariadb-dump for MariaDB installations or mysqldump otherwise.
• New Helper Function: A new function, get_mysql_dump_binary(), has been added to encapsulate the logic for determining the appropriate SQL dump binary, improving code organization and maintainability.

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[codecov[bot]]

Codecov Report

:x: Patch coverage is 0% with 33 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
php/utils.php	0.00%	33 Missing :warning:

:loudspeaker: Thoughts on this report? Let us know!

[manhphuc]

Thanks for the suggestions! I've applied the refactor to use early returns and added a debug message for the non-executable absolute-path case. I also updated the final log line to clearly indicate that it’s using the default dump command. Let me know if you'd like any further adjustments.