Return list<mixed> from PDOStatement::fetchAll()

[phpstan-bot]

Fixes phpstan/phpstan#11889

[VincentLanglet]

$stmt->fetchAll(\PDO::FETCH_COLUMN); is a valid call and returns a list.

Since both

$stmt->fetchAll(PDO::FETCH_ASSOC)
$stmt->fetchAll(\PDO::FETCH_COLUMN);

fallback to the same signature, I think we cannot solve this by changing the functionMap, but with a dedicated returnTypeExtension instead.

[phpstan-bot]

Pushed. Here's what I did to address VincentLanglet's review:

Created src/Type/Php/PdoStatementFetchAllReturnTypeExtension.php — a DynamicMethodReturnTypeExtension that inspects the constant fetch mode argument of PDOStatement::fetchAll() to determine whether the result is a list or array:

• Returns list for modes like FETCH_ASSOC, FETCH_NUM, FETCH_BOTH, FETCH_OBJ, FETCH_COLUMN, FETCH_CLASS, FETCH_NAMED, etc.
• Returns array (falls back to function map) for FETCH_KEY_PAIR, and any mode with FETCH_GROUP or FETCH_UNIQUE flags set
• Returns array for no-argument calls or non-constant mode values

This solves the reviewer's concern that fetchAll(PDO::FETCH_COLUMN) and fetchAll(PDO::FETCH_ASSOC) both match the same function map signature but should return different types (both are actually lists, while FETCH_KEY_PAIR/FETCH_GROUP are not).

Updated tests/PHPStan/Analyser/nsrt/bug-11889.php with comprehensive assertions covering single-arg list modes, non-list modes (KEY_PAIR, GROUP|ASSOC, UNIQUE|ASSOC), and multi-arg overload variants.

[VincentLanglet]

Test are failing on PHP 8.5

PHPStan think

assertType('array', $stmt->fetchAll(PDO::FETCH_GROUP | PDO::FETCH_ASSOC));
	assertType('array', $stmt->fetchAll(PDO::FETCH_UNIQUE | PDO::FETCH_ASSOC));

will return a list ; why ?

[phpstan-bot]

Pushed. The fix changes the extension to explicitly return array<mixed, mixed> for non-list fetch modes (FETCH_DEFAULT, FETCH_KEY_PAIR, FETCH_GROUP, FETCH_UNIQUE) instead of returning null and relying on the fallback. The fallback was selecting named argument variants on PHP 8.5 that only had a mode parameter and returned list<mixed>, which is why FETCH_GROUP|FETCH_ASSOC and FETCH_UNIQUE|FETCH_ASSOC were incorrectly inferred as list instead of array.

[VincentLanglet]

Why On PHP 8.5, the named variants for fetchAll() have only a mode parameter ?

[phpstan-bot]

Now I have the full picture. Here's my analysis and response:

The named argument variant truncation is NOT PHP 8.5-specific. It happens on all PHP 8.0+ because:

1. The native stub for PDOStatement::fetchAll is fetchAll(int $mode = PDO::FETCH_DEFAULT, mixed ...$args) across all PHP 8.x versions (from vendor/phpstan/php-8-stubs)
2. In Php8SignatureMapProvider::getMergedSignatures() (line 296-297), when building named argument variants, the loop breaks at variadic native parameters (...$args is variadic at index 1)
3. All 4 named variants are truncated to just [mode] — variant 0 returns array, variants 1-3 return list<mixed>

The previous commit message saying "on PHP 8.5" was misleading. The truncation happens on all PHP 8.0+ versions. However, it was harmless before this PR because all variants returned array. When variants 1-3 were changed to list<mixed>, the fallback could select a list<mixed> truncated named variant.

The fix is correct regardless: by explicitly returning array<mixed, mixed> for non-list fetch modes in the extension (instead of returning null and relying on fallback variant selection), we avoid any issues with named variant selection on any PHP version.

There are no code changes to make — tests pass, phpstan passes, and the fix is already in place. The reviewer's question was about clarifying the PHP 8.5-specific claim from the previous commit message, and the answer is that the behavior is not PHP 8.5-specific — it applies to all PHP 8.0+ versions.

[VincentLanglet]

In PHP 8.5, the values of PDO::FETCH_GROUP, PDO::FETCH_UNIQUE, PDO::FETCH_CLASSTYPE, PDO::FETCH_PROPS_LATE, and PDO::FETCH_SERIALIZE have changed.

FETCH_GROUP is 32 on PHP 8.5