Troubles with array_key_exists

[BOPOH]

https://psalm.dev/r/ed6528a596

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/ed6528a596

<?php

/**
 * @psalm-return ?1
 */
function get_key(): ?int
{
    return null;
}

/**
 * @psalm-return 1
 */
function get_key_1(): int
{
    return 1;
}

function get_key_null(): null
{
    return null;
}

/**
 * @psalm-return array{1?: int, ''?: int}
 */
function get_keys(): array
{
    return [];
}

function test(int $value): int {
    return $value;
}

$keys = get_keys();
$key = get_key();
if (array_key_exists($key ?? '', $keys)) {
    /** @psalm-trace $keys */;
    /** @psalm-trace $key */;
    test($keys[$key ?? ''] ?? 1);
}
if (array_key_exists((string)$key, $keys)) {
    /** @psalm-trace $keys */;
    /** @psalm-trace $key */;
    test($keys[(string)$key] ?? 1);
}

$key = get_key_1();
if (array_key_exists($key, $keys)) {
    /** @psalm-trace $keys */;
    /** @psalm-trace $key */;
    test($keys[$key] ?? 1);
}

$key = get_key_null();
if (array_key_exists($key ?? '', $keys)) {
    /** @psalm-trace $keys */;
    /** @psalm-trace $key */;
    test($keys[$key ?? ''] ?? 1);
}
if (array_key_exists((string)$key, $keys)) {
    /** @psalm-trace $keys */;
    /** @psalm-trace $key */;
    test($keys[(string)$key] ?? 1);
}

$key = '';
if (array_key_exists($key, $keys)) {
    /** @psalm-trace $keys */;
    /** @psalm-trace $key */;
    test($keys[$key] ?? 1);
}

Psalm output (using commit 08afc45):

INFO: Trace - 39:30 - $keys: array{''?: int, 1?: int}

INFO: Trace - 40:29 - $key: 1|null

ERROR: PossiblyUndefinedArrayOffset - 41:10 - Possibly undefined array key  on array{''?: int, 1?: int}

ERROR: PossiblyNullArgument - 41:10 - Argument 1 of test cannot be null, possibly null value provided

INFO: Trace - 44:30 - $keys: array{''?: int, 1?: int}

INFO: Trace - 45:29 - $key: 1|null

ERROR: PossiblyUndefinedArrayOffset - 46:10 - Possibly undefined array key  on array{''?: int, 1?: int}

ERROR: PossiblyNullArgument - 46:10 - Argument 1 of test cannot be null, possibly null value provided

INFO: Trace - 51:30 - $keys: array{''?: int, 1: int}

INFO: Trace - 52:29 - $key: 1

ERROR: TypeDoesNotContainType - 57:22 - Type null for $key is always !null

INFO: Trace - 58:30 - $keys: array{''?: int, 1?: int}

INFO: Trace - 59:29 - $key: null

ERROR: TypeDoesNotContainType - 60:16 - Type null for $key is always !null

INFO: Trace - 63:30 - $keys: array{''?: int, 1?: int}

INFO: Trace - 64:29 - $key: null

INFO: Trace - 70:30 - $keys: array{'': int, 1?: int}

INFO: Trace - 71:29 - $key: ''

[kkmuffme]

Can you please describe what the issue is in a short text ?

[BOPOH]

@kkmuffme if array_key_exists($key, $array) returns true, then $key exists in array

i.e. if array_key_exists((string)$key, $keys) returns true, then $keys[(string)$key] exists, but psalm thows warning ERROR: [PossiblyUndefinedArrayOffset](https://psalm.dev/167) - 46:10 - Possibly undefined array key on array{''?: int, 1?: int} - that is the error

[kkmuffme]

Happens because psalm does not store all evaluations but only variables. I don't think this will ever get fixed, especially since you can just assign $k = $key ?? ''; and use that instead of using the null coalesce twice.