`AbstractActiveRecord::newValues()` incorrectly marks DateTimeInterface attribute as changed

[darealfive]

Description

The newValues() method fails to correctly detect changes for DateTimeType related types, e.g. DateTimeInterface respectively DateTimeImmutable.

Specifically:

• DateTimeImmutable / DateTimeInterface values are compared using strict comparison (!==), causing two instances representing the same moment to be always treated as changed (incorrectly), because two objects are never object-equal.

This affects Active Record dirty-checking and can cause unnecessary record updates and therefore subsequent problems.

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Steps to Reproduce

1. Load an Active Record model from the database with at least one DateTime column and make sure it gets mapped to DateTimeImmutable.
2. ...either assign a new DateTimeImmutable instance with the same date/time value. ... or leave the value as is.
3. Call newValues() or attempt to save the model.Expected: The attribute should not be marked as dirty.

Actual: The attribute is considered as changed (dirty) incorrectly.

---

Expected Behavior

• DateTimeInterface values should be compared using loose comparison (==) to compare actual date/time values rather than object identity.

---

Proposed Fix

/**
 * Returns the property values that have been modified since they're loaded or saved most recently.
 *
 * The comparison of new DateTimeInterface objects with old values uses `==`.
 * The comparison of all other values uses `===`.
 *
 * @param array|null $propertyNames The names of the properties whose values may be returned if they're changed
 *                                  recently. If `null`, {@see propertyNames()} will be used.
 *
 * @return array The changed property values (name-value pairs).
 *
 * @psalm-return array<string, mixed>
 */
#[Override]
public function newValues(array|null $propertyNames = null): array
{
    $values    = $this->propertyValues($propertyNames);
    $oldValues = $this->oldValues();
    if ($oldValues === []) {
        return $values;
    }

    $result = array_diff_key($values, $oldValues);
    foreach (array_diff_key($values, $result) as $name => $value) {
        if ($value instanceof DateTimeInterface) {
            if ($value != $oldValues[$name]) {
                $result[$name] = $value;
            }
        } else {
            if ($value !== $oldValues[$name]) {
                $result[$name] = $value;
            }
        }
    }

    return $result;
}

---

Notes

I think this behavior avoids false positives when using immutable date/time objects. You may update \Yiisoft\ActiveRecord\ActiveRecordInterface::newValues documentation with the provided one and leave the actual implementation documentation empty (as it is currently).

Package version

1.0.0

PHP version

PHP 8.4.15 (cli)