What causes "Given property is not readonly." in doctrine/orm?

Guard the wrapping: only construct ReflectionReadonlyProperty when $reflectionProperty->isReadOnly() is true.

doctrine/orm · error · InvalidArgumentException

Given property is not readonly.

Error message

Given property is not readonly.

What it means

ReflectionReadonlyProperty extends ReflectionProperty to allow exactly one initialization write to a readonly property (setValue passes through while uninitialized; a later differing write throws). Its constructor asserts the wrapped ReflectionProperty is readonly; LegacyReflectionFields only wraps properties where isReadOnly() already returned true, so this InvalidArgumentException signals direct misuse of the class.

Source

Thrown at src/Mapping/ReflectionReadonlyProperty.php:24

use InvalidArgumentException;
use LogicException;
use ReflectionProperty;

use function assert;
use function func_get_args;
use function func_num_args;
use function is_object;
use function sprintf;

/** @internal */
final class ReflectionReadonlyProperty extends ReflectionProperty
{
    public function __construct(
        private readonly ReflectionProperty $wrappedProperty,
    ) {
        if (! $wrappedProperty->isReadOnly()) {
            throw new InvalidArgumentException('Given property is not readonly.');
        }

        parent::__construct($wrappedProperty->class, $wrappedProperty->name);
    }

    public function getValue(object|null $object = null): mixed
    {
        return $this->wrappedProperty->getValue(...func_get_args());
    }

    public function setValue(mixed $objectOrValue, mixed $value = null): void
    {
        if (func_num_args() < 2 || $objectOrValue === null || ! $this->isInitialized($objectOrValue)) {
            $this->wrappedProperty->setValue(...func_get_args());

            return;
        }

View on GitHub (pinned to d9b9ff7301)

Solutions

Guard the wrapping: only construct ReflectionReadonlyProperty when $reflectionProperty->isReadOnly() is true.
Reuse the library path (LegacyReflectionFields / getClassMetadata()->getReflectionProperty()) instead of constructing the wrapper yourself.
If the property is intentionally mutable, use the plain ReflectionProperty.

Example fix

// before
$refl = new ReflectionReadonlyProperty($plainRefl); // $plainRefl not readonly -> InvalidArgumentException

// after
$refl = $plainRefl->isReadOnly()
    ? new ReflectionReadonlyProperty($plainRefl)
    : $plainRefl;

Defensive patterns

Strategy: validation

Validate before calling

$refl = $reflectionProperty->isReadOnly()
    ? new ReflectionReadonlyProperty($reflectionProperty)
    : $reflectionProperty;

Prevention

Only wrap properties whose isReadOnly() is true.
Use getClassMetadata()->getReflectionProperty() instead of constructing wrappers yourself.
When removing readonly from a property, search for any saved/custom wrappers that reference it.

When it happens

Trigger: Directly calling new ReflectionReadonlyProperty($reflectionProperty) with a property that lacks the readonly modifier; keeping a previously-created wrapper after removing readonly from the property; custom reflection-service implementations wrapping properties unconditionally.

Common situations: Custom tooling copying LegacyReflectionFields::getAccessibleProperty() logic without the isReadOnly() branch; refactoring a property from readonly to mutable while cached/custom reflection wrappers persist.

Related errors

AI-assisted analysis of doctrine/orm@d9b9ff7301 (2026-08-21). Data as JSON: /api/errors/bb5b461b65ea645c. Report an issue: GitHub.