symfony/http-kernel · error · LogicException

You cannot pass non-empty bodies as the Mime component is…

Error message

You cannot pass non-empty bodies as the Mime component is not installed. Try running "composer require symfony/mime".

What it means

HttpClientKernel::getBody() converts non-GET/HEAD request bodies into a Mime TextPart for the outgoing HTTP request. Converting a non-empty body requires symfony/mime (AbstractPart); without it, passing a non-empty body throws this LogicException.

Solutions

Run composer require symfony/mime
Or send GET/HEAD requests only, or requests with empty bodies
Or provide the body as a pre-built AbstractPart yourself (still requires mime)

Example fix

// before (throws for POST with content)
$client->request('POST', '/api', ['body' => 'data']);
// after
composer require symfony/mime
$client->request('POST', '/api', ['body' => 'data']);

Defensive patterns

Strategy: validation

Validate before calling

if ($request->getContent() !== '' && !class_exists(\Symfony\Component\Mime\Part\AbstractPart::class)) {
    throw new \LogicException('symfony/mime required for non-empty bodies; run composer require symfony/mime');
}
$client->request($method, $uri, $options);

Try / catch

try {
    $client->request('POST', $uri, ['body' => $payload]);
} catch (\LogicException $e) {
    $logger->error($e->getMessage());
}

Prevention

composer require symfony/mime whenever symfony/http-client is used with request bodies
Avoid sending request bodies on GET/HEAD
Check composer.lock includes transitive mime dependency

When it happens

Trigger: Sending a request with a non-empty body (POST/PUT/PATCH with content, or form data) through HttpClientKernel when symfony/mime is not installed. GET/HEAD requests are unaffected (return null).

Common situations: symfony/http-client installed but symfony/mime not pulled in as a dependency; minimal composer install that omits transitive requirements in older setups.

Understand the failure class

Background: "X is not installed. Please install it with pip install Y": missing optional dependency errors — ImportError/ValueError raised when a library's optional extra was never installed — this error's family across 22 libraries.

Related errors

AI-assisted analysis of symfony/http-kernel@aa3a39d728 (2026-09-13). Data as JSON: /api/errors/cea2ba9068c69b00. Report an issue: GitHub.

Appendix: source

Thrown at HttpClientKernel.php:86

        try {
            return new Response($response->getContent(!$catch), $response->getStatusCode(), $headers);
        } catch (\TypeError) {
            // BC with Symfony < 8.1
            $response = new Response($response->getContent(!$catch), $response->getStatusCode());
            $response->headers = $headers;

            return $response;
        }
    }

    private function getBody(Request $request): ?AbstractPart
    {
        if (\in_array($request->getMethod(), ['GET', 'HEAD'], true)) {
            return null;
        }

        if (!class_exists(AbstractPart::class)) {
            throw new \LogicException('You cannot pass non-empty bodies as the Mime component is not installed. Try running "composer require symfony/mime".');
        }

        if ($content = $request->getContent()) {
            return new TextPart($content, 'utf-8', 'plain', '8bit');
        }

        $fields = $request->request->all();
        foreach ($request->files->all() as $name => $file) {
            $fields[$name] = DataPart::fromPath($file->getPathname(), $file->getClientOriginalName(), $file->getClientMimeType());
        }

        return new FormDataPart($fields);
    }

    private function getHeaders(Request $request): array
    {
        $headers = [];
        foreach ($request->headers as $key => $value) {

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