v 3.0.0 Unexpected token u in JSON (json parse undefined) when ../create/?someparams

Steps to reproduce: #/resource/create?anyParams Unexpected token u in JSON at position 0 seems json is trying to parse undefined variable

Environment

• React-admin version: 3.0.0

[mutewinter]

I also just discovered another, seemingly more intended, way to do this:

https://github.com/marmelab/react-admin/blob/master/docs/CreateEdit.md#prefilling-a-create-record

Using state it’s possible to pass pre-filled data to create without using query params at all.

const AddNewCommentButton = ({ record }) => (
  <Button
    component={Link}
    to={{
      pathname: "/comments/create",
      state: { post_id: record.id },
    }}
    label="Add a comment"
  >
    <ChatBubbleIcon />
  </Button>
);

[fzaninotto]

In 3.0, the way to pre-fill some fields in the create form is to pass a stringified object as the source URL parameter. That’s what the CloneButton does:

export const CloneButton = ({
    basePath = '',
    label = 'ra.action.clone',
    record = {},
    icon = <Queue />,
    ...rest
}) => (
    <Button
        component={Link}
        to={{
            pathname: `${basePath}/create`,
            search: stringify({ source: JSON.stringify(omitId(record)) }),
        }}
        label={label}
        onClick={stopPropagation}
        {...sanitizeRestProps(rest)}
    >
        {icon}
    </Button>
);

In v2, this feature didn’t use the fields of the source get parameter, but all the get parameters. This lead to hard to fix bugs like #3966.

The advanced tutorials were indeed written for v2. For v3, the right syntax should be:

const AddNewCommentButton = ({ record }) => (
  <Button
    component={Link}
    to={{
      pathname: "/comments/create",
-     search: `?post_id=${record.id}`,
+     search: `?source=${JSON.stringify({ post_id: record.id })}`,
    }}
    label="Add a comment"
  >
    <ChatBubbleIcon />
  </Button>
);

Sorry for not mentioning it in the UPGRADE guide - we figured that, since both the Create page and the CloneButton were changed at the same time, it was a backwards compatible change. We forgot that we had documented the inner workings of CloneButton in an advanced tutorial, which made it a public API.

So this is a breaking change, not a bug. I’ll document it in the Upgrade guide.

Also, there is indeed a small bug: useCreateController should not try to parse the search.source field if it’s not present. I’ll also fix it in a future PR.