symfony/http-kernel · error · LogicException

Users will expect the alias of the default extension of a…

Error message

Users will expect the alias of the default extension of a bundle to be the underscored version of the bundle name ("%s"). You can override "Bundle::getContainerExtension()" if you want to use "%s" or another alias.

What it means

Symfony's Bundle::getContainerExtension() auto-discovers a bundle's DependencyInjection extension and enforces the naming convention: the extension alias must be the underscored version of the bundle name with the "Bundle" suffix stripped (e.g. AcmeFooBundle -> acme_foo). A LogicException is thrown when the extension class exists but its getAlias() returns something else, because container parameter/keys would confuse users.

Solutions

1. Rename the extension's getAlias() return value to Container::underscore(basename-without-Bundle-suffix), e.g. return 'acme_foo';
2. Alternatively rename the Extension class so the conventional getAlias() computes the correct alias automatically.
3. If a non-conventional alias is truly intended, override Bundle::getContainerExtension() explicitly (as the message says) so the convention check is bypassed.

Example fix

// before
class AcmeFooExtension extends Extension
{
    public function getAlias(): string
    {
        return 'foo';
    }
}
// after
class AcmeFooExtension extends Extension
{
    public function getAlias(): string
    {
        return 'acme_foo';
    }
}

$expected = \Symfony\Component\DependencyInjection\Container::underscore(preg_replace('/Bundle$/', '', $bundle->getName()));
if ($extension->getAlias() !== $expected) {
    // fix alias before registering
}

try { $ext = $bundle->getContainerExtension(); } catch (\LogicException $e) { /* fix extension alias in DI extension class */ }

When it happens

Trigger: Registering a bundle whose Extension class (e.g. AcmeFooBundle\DependencyInjection\AcmeFooExtension) returns an alias from getAlias() that does not equal Container::underscore('AcmeFoo'); typically when getAlias() is overridden to return a custom string, or the extension class name deviates from the convention so the parent getAlias() fallback derives a wrong alias.

Common situations: Renaming a bundle without renaming its Extension class or alias; hand-writing getAlias() to a shorter/prettier name like 'foo' while the bundle is 'AcmeFooBundle'; copying an extension from another bundle and forgetting to update getAlias().

Understand the failure class

Background: "invalid id" errors: invalid identifier format — why libraries reject IDs before lookup, and how to fix them — this error's family across 37 libraries.

Related errors

• Controller " " has required constructor arguments and does…
• Controller " " cannot be fetched from the container because…
• Request payload contains invalid "form" data.
• Unsupported format: " ".
• Request payload contains invalid

AI-assisted analysis of symfony/http-kernel@aa3a39d728 (2026-09-13). Data as JSON: /api/errors/b183773fd13260a2. Report an issue: GitHub.

Appendix: source

Thrown at Bundle/Bundle.php:48

     *
     * @throws \LogicException
     */
    public function getContainerExtension(): ?ExtensionInterface
    {
        if (!isset($this->extension)) {
            $extension = $this->createContainerExtension();

            if (null !== $extension) {
                if (!$extension instanceof ExtensionInterface) {
                    throw new \LogicException(\sprintf('Extension "%s" must implement Symfony\Component\DependencyInjection\Extension\ExtensionInterface.', get_debug_type($extension)));
                }

                // check naming convention
                $basename = preg_replace('/Bundle$/', '', $this->getName());
                $expectedAlias = Container::underscore($basename);

                if ($expectedAlias != $extension->getAlias()) {
                    throw new \LogicException(\sprintf('Users will expect the alias of the default extension of a bundle to be the underscored version of the bundle name ("%s"). You can override "Bundle::getContainerExtension()" if you want to use "%s" or another alias.', $expectedAlias, $extension->getAlias()));
                }

                $this->extension = $extension;
            } else {
                $this->extension = false;
            }
        }

        return $this->extension ?: null;
    }

    public function getNamespace(): string
    {
        return $this->namespace ??= false === ($pos = strrpos(static::class, '\\')) ? '' : substr(static::class, 0, $pos);
    }

    public function getPath(): string
    {

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