Single createSelector function doesn't get state passed in.

[michalvankodev]

Hello,
This took me some time to find but I've ran into this issue.
When I have only simple selector

const somethingSelector = createSelector(
  (state: StoreState) => {
    return {
      state.something
    };
  }
);

It will not get the state passed in.

I've found that this PR: #1515 has introduced this issue.
Not very sure why the function is not called with state as an argument but it broke my application immediately.

Minimal reproduction of the bug/regression with instructions:

Expected behavior:

Nothing should be broken by a not-breaking release.
Use of createSelector without any previous selectors is broken.

Versions of NgRx, Angular, Node, affected browser(s) and operating system(s):

Other information:

I would be willing to submit a PR to fix this issue

[ ] Yes (Assistance is provided if you need help submitting a pull request)
[ X] No. I think reverting the previous PR should be done. And a proper fix for the issue it was intented to fix

[timdeschryver]

I think this was an undesired outcome, due to implementing the selector with props feature (more specifically to allow the createSelector with only a props selector.
If you take a look at an example from v6.0.x, the state within the selector is also
undefined - repro.

The PR #1515 reverts this change, but was indeed a breaking change.

[timdeschryver]

With the knowledge gained, I think it wasn't a great idea to allow these selectors with props working directly with the projection function without the need of a selector.

Concrete this means that the following won't be possible anymore

const getTodosById = createSelector(
  (state: TodoAppSchema, id: number) => {
    return state.todos.find(p => p.id === id);
  }
);

But would need to be written as:

const getTodosById = createSelector(
  (state: TodoAppSchema) => state,
  (state: TodoAppSchema, id: number) => {
    return state.todos.find(p => p.id === id);
  }
);

// or 

const getTodosById = createSelector(
  (state: TodoAppSchema) => state.todos,
  (todos: Todo[], id: number) => {
    return todos.find(p => p.id === id);
  }
);

This would also be in line with the reduxjs/reselect library which has as API
createSelector(...inputSelectors | [inputSelectors], resultFunc).

This would be a breaking change that we could add for v8.

Would this be OK for you @brandonroberts ?

To clarify, this would also mean that the example snippet would also be an invalid selector and would lead to errors (as pre v6.1.2):

const somethingSelector = createSelector(
  (state: StoreState) => {
    return {
      state.something
    };
  }
);

// should be written as

const somethingSelector = createSelector(
  state => state,
  (state: StoreState) => {
    return {
      state.something
    };
  }
);

[brandonroberts]

@timdeschryver I'm fine with the breaking change to make the usage more consistent.

[timdeschryver]

👍 I will submit a PR