fix(eloquent): talk to MySQL the way WordPress does

[gfazioli]

Follow-up to #113, found while fixing #110.

The problem

The MySQL connection hard-coded utf8 / utf8_unicode_ci and passed DB_HOST as the host. Measured on a local site: MySQL 8.4, tables utf8mb4_unicode_520_ci, DB_CHARSET 'utf8' (which WordPress raises to utf8mb4 itself), and a sql_mode without STRICT_*.

• Writing an emoji through Eloquent failed: SQLSTATE[HY000]: General error: 3988 Conversion from collation utf8mb3_unicode_ci into utf8mb4_unicode_520_ci impossible for parameter.
• An emoji written by WordPress came back through Eloquent as emoji ? ok.
• DB_HOST localhost:/tmp/mysql.sock did not connect: SQLSTATE[HY000] [2002] Can't assign requested address. host:port already worked, because PDO accepts it.

The fix

The connection now follows WordPress's own:

• charset and collation: $wpdb->charset and $wpdb->collate, what WordPress actually uses on its connection. Not DB_CHARSET, which here says utf8. An empty collation is left out instead of being sent as collate ''.
• host: DB_HOST goes through $wpdb->parse_db_host(), as in wpdb::db_connect(). That gives Laravel a port, a unix_socket, and an IPv6 host in brackets when mysqlnd is loaded.
• Without $wpdb: the host is passed as it is and the charset is utf8mb4.

SQLite (#113) is unchanged.

Tests

• tests/Unit/EloquentTest.php has 10 tests, 6 of them new. A stand-in $wpdb answers parse_db_host() the way WordPress does, and the tests check how that answer becomes Laravel's connection: charset and collation, port, socket, IPv6 brackets, empty collation, an unparsable host, no $wpdb. The full suite passes: 158 tests.
• Live, eloquent-live-smoke.sh in the workspace, in the bench (MySQL) and in a local @wp-playground/cli (SQLite):

Check	v2.0.11	this branch
MySQL: connection charset/collation = WordPress's (utf8mb4, utf8mb4_unicode_520_ci)	✗ utf8 / utf8_unicode_ci	✓
MySQL: an emoji written by Eloquent reaches the table intact	✗ error 3988	✓
MySQL: an emoji written by WordPress is read back intact by Eloquent	✗ emoji ? ok	✓
MySQL: DB_HOST localhost, localhost:3306, 127.0.0.1:3306 connect	✓	✓
MySQL: DB_HOST localhost:/tmp/mysql.sock connects	✗	✓
SQLite: the Database demo's 11 Eloquent examples	✓	✓

The IPv6 form isn't in the live run: this MySQL listens on 127.0.0.1 only, and mysqli refuses [::1] too. The brackets are covered by the unit test, which mirrors wpdb::db_connect().

[Copilot]

Copilot review overview

🟢 Approval recommended

No unresolved blocking issues were identified.

Review effort: Lite
Findings: None

What changed in this PR

Updates Eloquent’s MySQL connection to match WordPress’s charset, collation, and host parsing while preserving SQLite support.

Changes:

• Uses $wpdb settings with an utf8mb4 fallback.
• Supports ports, Unix sockets, and IPv6 hosts.
• Adds unit coverage for MySQL configuration variants.

File	Description
tests/​Unit/​EloquentTest.php	Tests charset, collation, host parsing, and fallback behavior.
src/​Database/​Eloquent.php	Implements WordPress-compatible MySQL connection settings.

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