"Unable to unserialize value" error on GraphQL query 2.3-develop branch

Question

I'm trying out the GraphQL API on the 2.3-develop branch. On a clean Magento install, all queries return:

 "errors": [
        {
            "debugMessage": "Unable to unserialize value.",
            "message": "Internal server error",
            "category": "internal",
            "trace": [
                {
                    "file": "/magento/app/code/Magento/GraphQl/Controller/GraphQl.php",
                    "line": 102,
                    "call": "Magento\\Framework\\Serialize\\Serializer\\Json::unserialize('{\n    products(search: \" \"){\n        total_count\n\t}\n}')"
                },
            {

I'm sending a HTTP POST request to http://magento-shop-host/graphql

With the headers:

• Accept: application/json
• Content-Type: application/json

Answer 1

run php bin/magento setup:upgrade

Answer 2

I had the same issue and was not able to fix it so far. The only thing i managed to get this solved is doing the following:

in the file /vendor/magento/module-graph-ql/Controller/GraphQl.php On line 102 (or in a later version line 111) you have the following

$data = $this->jsonSerializer->unserialize($request->getContent());

I replaced this via a composer patch with the following

$content = ($request->getContent() === '') ? '{}' : $request->getContent();
$data = $this->jsonSerializer->unserialize($content);

I had this issue of GraphiQL requests working perfectly. but upon implementing this same query with react-apollo it preflight checks with a OPTIONS query that will return an Unable to unserialize value error.

Hopefully this will help other