LB4 todo-list example gives Error: Property "todoListId" cannot be changed!

[foobarrrz]

I have cloned the project using cli "lb4 example todo-list" without modifying anything.

After I Inserted new record to "todo-list" model, I got the response.
{ "id": 3, "title": "newToDoList", "color": "red" }

then I use id = 3 as an input for POST /todo-lists/{id}/todos.

Unhandled error in POST /todo-lists/3/todos: 500 Error: Property "todoListId" cannot be changed!
    at Object.constrainDataObject (D:\Projects\NodeJs\lbex\loopback4-example-todo-list\node_modules\@loopback\repository\dist\repositor
ies\constraint-utils.js:49:19)
    at DefaultHasManyRepository.create (D:\Projects\NodeJs\lbex\loopback4-example-todo-list\node_modules\@loopback\repository\dist\rela
tions\has-many\has-many.repository.js:21:59)
    at process._tickCallback (internal/process/next_tick.js:68:7)

I also try to create the relation model myself following the example.
https://loopback.io/doc/en/lb4/HasMany-relation.html
But it also give the same error.

[nabdelgadir]

When you're trying to do a POST request for /todo-lists/{id}/todos, there's no need to supply the todoListId property since it's the one that replaces {id} in /todo-list/{id}/todos e.g. /todo-list/3/todos.

So I created your TodoList model: { "id": 3, "title": "newToDoList", "color": "red" }. Then I did a POST request - POST /todo-lists/3/todos with the following body:

{
  "id": 0,
  "title": "sample todo",
  "desc": "sample description",
  "isComplete": false
}

To which I received the following response body (and a 200 status code):

{
  "id": 5,
  "title": "sample todo",
  "desc": "sample description",
  "isComplete": false,
  "todoListId": 3
}

I believe when you add the todoListId property to your POST body, it passes this check, which is where the error comes from.

I'm thinking we can add this information to the documentation, specifically the HasMany relation page, what do you think?

[nabdelgadir]

Acceptance Criteria

• Add a section to the HasMany relation docs explaining the format of the request body when doing a POST request (need to exclude the id of the "parent" [Category in the current docs] entity)

[emonddr]

@b-admike will look to see if there is an existing bug related to the this check url mentioned above.

[bajtos]

Most people don't read docs. Can we instead fix the constraint check to recognize the situation where the requested data is not changing the immutable key and don't report a false error?

[nabdelgadir]

@b-admike if you can find the issue that's related to that check, we can close this issue. Otherwise, we can modify this issue to fix the constraint instead of the docs (or close this one and open a new issue).

[bajtos]

I think the problem is has been described here first: #1719