[wp-trac] [WordPress Trac] #64703: Code Modernization: Replace void in PHPDoc union return types with null in class-wpdb.php

[WordPress Trac]

#64703: Code Modernization: Replace void in PHPDoc union return types with null in
class-wpdb.php
--------------------------+-----------------------------
 Reporter:  apermo        |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Database      |    Version:  4.3
 Severity:  normal        |   Keywords:
  Focuses:                |
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 Following up on [#64694] which fixed `paginate_links()`, this ticket
 addresses 3 instances in `class-wpdb.php` where `@return` annotations
 incorrectly use `void` as part of a union type.

 The `|void` pattern was introduced in WordPress 4.3 via [32654] for
 `prepare()` and `check_connection()`, and in WordPress 5.5 via [47944] for
 `get_row()`.

 === Why this matters ===

 In PHP's type system, `void` means "the function does not return a value"
 and '''cannot''' be part of a union type (this is a compile error in PHP
 8.0+). When a function uses bare `return;` or falls off the end without
 returning, the actual runtime value is `null`. Therefore `@return
 Type|void` should be `@return Type|null`.

 This affects:
 * Static analysis tools (PHPStan, Psalm)
 * IDE autocompletion and type inference
 * Developer expectations about return values

 === Backward Compatibility ===

 This is a safe, non-breaking change. As demonstrated by @westonruter in
 the [https://github.com/WordPress/wordpress-
 develop/pull/10999#pullrequestreview-3839142928 #64694 PR review],
 `return;` and `return null;` are identical at runtime across every PHP
 version from 4.3.0 through 8.5.3: https://3v4l.org/3KQC8

 === Proposed Changes ===

 For each instance:
 1. Update the `@return` annotation to replace `void` with `null` (or
 remove `|void` where the function always returns a typed value)
 2. Change bare `return;` statements to `return null;`
 3. Update description text to say "null" instead of "void" / "nothing"

 === Affected Functions ===

 ||= Function =||= Line =||= Current =||= Recommendation =||= Since =||
 || `prepare()` || 1456 || `string|void` || `string|null` || 4.3 ||
 || `check_connection()` || 2120 || `bool|void` || `bool` (void incorrect —
 always returns bool or terminates) || 4.3 ||
 || `get_row()` || 3059 || `array|object|null|void` || `array|object|null`
 (void redundant — already includes null) || 5.5 ||

 **Note on `prepare()`:** Uses bare `return;` on error paths. The change to
 `return null;` is safe, but the error-path behavior should be reviewed to
 confirm `null` is the intended signal for "no query".

 See [#64694] for prior art.

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Ticket URL: <https://core.trac.wordpress.org/ticket/64703>
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