Request body works when hardcoded, fails when passed as variable

[Javi_V]

I have an editable table and want to save the changes to the backend of my application. To do so, I use three elements:

• The table's changesetArray
• An OpenAPI resource (with a POST endpoint that takes an array of changes as a request body)
• A transformer that maps the rows from the changeset to the format the API call needs.

The problem?

When I hardcode the transformer's value in the request body, it works. When I use the transformer's value as a variable in the request body, it fails with this error message:

Unexpected token { in JSON at position 1

This is the code in the transformer:

let changeset = {{ parkingTable.changesetArray }};

let changesetArray = Object.entries(changeset);

changesetArray = changesetArray.map(
  ([key, row]) => ({
    carOwnerId: row.id.toString(),
    parkingSpotId: row.parkingSpotId.toString()
  })
)

return changesetArray;

It just renames two fields from the changeset entries and feeds them to the API call:

However, if I just copy the result of the transformer and paste it in the request body, it works, which makes no sense:

I don't understand why the same value fails when passed as a variable, and works when hardcoded.

Can you help me out?

[MiguelOrtiz]

Hey there @Javi_V,

Could it be that your API expects a string, but the variable is being read as an object. You can try {{ JSON.stringify (formattedChangeSet.value) }}

[Javi_V]

Nope, same problem:

Unexpected token { in JSON at position 1

Ironically, when I hardcode the exact same value that the transformer produces, it works:

[{"carOwnerId":"3","parkingSpotId":"7"},{"carOwnerId":"2","parkingSpotId":"5"}]

As you can see here, I'm passing an array, and it works. And it's literally the same output that the transformer produces.

As an extra hint, I took a look at the network tab on my browser, and copied the body of the requests (hardcoded and variable reference) and I see that it's different:

hardcoded (correct):

"requestBodyParams": {
      "0": [
        {
          "carOwnerId": "3",
          "parkingSpotId": "7"
        },
        {
          "carOwnerId": "2",
          "parkingSpotId": "5"
        }
      ],
      "length": 1
    },

Transformer result reference:

"requestBodyParams": {
  "length": 0
},

Do these details offer any context?

[MiguelOrtiz]

How strange...

Could you take a look at your API's status by clicking on "View State" when right clicking on it and see what the query is evaluating to?

[Javi_V]

Yes, this is the query's state after calling it with the transformer's value:

and this is the query after calling it with the hardcoded value:
[{"carOwnerId":"7","parkingSpotId":"4"},{"carOwnerId":"11","parkingSpotId":"3"}]

[MiguelOrtiz]

This is indeed strange. I read a similar issue here, albeit with a different API, but there wasn't a solution, rather a hacky workaround.

I'll let other members of the forum, or the retool team to chip into this one. Sorry I was not able to help!

[lindakwoo]

@Javi_V ,

Yes, this must be frustrating if your transformer produces the same exact result as the hardcoded data. Can you try it with a regular javascript query instead of a transformer?

Also, would you mind exporting your json to me so I can take a look at your data? Please also provide the api resource. Thanks!

[lindakwoo]

@Javi_V,
Just checking in to see if your issue has been resolved.

[paqml]

I just want to share that I notice the same problem too on my local retool.
while troubleshooting I can confirm from my logs that when this problem occurs it is not hitting my API at all.
I suspect it is not treating {{ as a reference to a variable and just tries to parse it like it is the raw input thus complaining about the unexpected { at 1 . so retool just stops and not make the request
I'm still trying to figure out why, but currently clueless.

[paqml]

for extra info, for my case I tried getting the value from a variable or a javascript query data.
i didn't use a transformer

[paqml]

I found more clues as I work on it further. so I'm calling an OpenAPI that is expecting an array of objects on the request body.

[
    {
      "attribute": "location",
      "values": [
        "New York",
        "Los Angeles"
      ]
    }
]

when I changed the API to expect instead a field that wraps the array so it is like

{
  "filters": [
    {
      "attribute": "location",
      "values": [
        "New York",
        "Los Angeles"
      ]
    }
  ]
}

That made the request body input from retool different and not complained with the reference value anymore and was able to run the API query properly.