React + Apollo "Getting Started" Error in Prisma Playground - reactjs

Question

I am in the Getting Started React + Apollo chapter: https://www.howtographql.com/react-apollo/1-getting-started/
When I enter the following query in the Prisma Playground (as the tutorial tells me to do):
mutation CreatePrismaLink {
post(
description: "Prisma gives you a powerful database toolkit 😎"
url: "https://prisma.io"
) {
id
}
}
mutation CreateApolloLink {
post(
description: "The best GraphQL client for React"
url: "https://www.apollographql.com/docs/react/"
) {
id
}
}
I get this error message that I don't understand. It seems to be something about the server
"errors": [
{
"message": "Argument id for data.postedBy.connect.id must not be null. Please use undefined instead.\n",
"locations": [
{
"line": 2,
"column": 3
}
],
"path": [
"post"
],
"extensions": {
"code": "INTERNAL_SERVER_ERROR",
"exception": {
"clientVersion": "2.12.1",
"stacktrace": [
"Error: Argument id for data.postedBy.connect.id must not be null. Please use undefined instead.",
"",
" at Document.validate (C:\\Users\\shanm\\hackernews-react-apollo\\server\\node_modules\\#prisma\\client\\runtime\\index.js:77413:19)",
" at NewPrismaClient._executeRequest (C:\\Users\\shanm\\hackernews-react-apollo\\server\\node_modules\\#prisma\\client\\runtime\\index.js:79065:17)",
" at C:\\Users\\shanm\\hackernews-react-apollo\\server\\node_modules\\#prisma\\client\\runtime\\index.js:79002:52",
" at AsyncResource.runInAsyncScope (async_hooks.js:197:9)",
" at NewPrismaClient._request (C:\\Users\\shanm\\hackernews-react-apollo\\server\\node_modules\\#prisma\\client\\runtime\\index.js:79002:25)",
" at Object.then (C:\\Users\\shanm\\hackernews-react-apollo\\server\\node_modules\\#prisma\\client\\runtime\\index.js:79119:39)",
" at processTicksAndRejections (internal/process/task_queues.js:93:5)"
]
}
}
}
],
"data": null
}
please help me find the problem?

Answer 1

This is old but in case somebody else hits this issue and Googles it like me:
Unfortunately the answer here didn't work for me, but the solution is something that was covered in the Node+GraphQL tutorial, which you might not be able to figure out on your own:
In order to post you have to first create a user and then be authorized as that user. The mutation to create a user is listed as an example on the page, but unfortunately the author forgot to instruct the reader to run it before trying to create a post.
Paste this into the playground to create a user
mutation {
signup(name: "Sarah", email: "sarah#prisma.io", password: "graphql") {
token
user {
id
}
}
}
Copy the token that is returned
Open the "HTTP Headers" pane in the bottom left
Enter this with your token:
{
"Authorization": "Bearer TOKEN_HERE"
}
Now you can run the mutations to create the posts

Answer 2

That's because the server has been written with the business rule in mind that a Post will always belong to a User. The database has a NOT NULL postedById field on the Link table i.e. a post will always have a user id attached to it. You need to make postedById field nullable in the Link model in the Prisma ORM schema. To fix this, make the following changes on server side code and relaunch the server
In the server folder go to schema.prisma file, and make both fields postedBy and postedById optional/nullable by suffixing them with ?
postedBy? User #relation(fields: [postedById], references:[id])
postedById? Int
Then run the following command to recreate database with the changes
npx prisma migrate reset
Update the post resolver function in Mutation.js file to replace the line
postedBy: { connect: { id: userId } }
with
postedById: userId,
because prisma connect api does not accept a null value