Change dynamic field interfaces

[mizdra]

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Motivation

• The get function does not return a usable type.
  • The type of get('author') is Promise<OptionalAuthor | undefined>.
  • OptionalAuthor means { id?: string | undefined, name?: string | undefined, email?: string | undefined }.
  • All fields of author may be undefined. This is inconvenient for the user.
  • Therefore, get function is not very useful.
• Dependent Field is not simple to define.
  • What it means...
    • Call get(...): get('name')
    • Add await keyword before get(...): await get('name')
    • Prepare default value: (await get('name')) ?? 'defaultName'
    • Compute the field: `${(await get('name')) ?? 'defaultName'}@yuyushiki.net`
    • Wrap with dynamic function: dynamic(async ({ get }) => `${(await get('name')) ?? 'defaultName'}@yuyushiki.net`)
  • Many steps are required. It is not simple.
  • I would like to define it more simply.

Proposal

Change the interface as follows:

Case. 1: Use seq in defaultFields and .build() function

Before

const BookFactory = defineBookFactory({
  defaultFields: {
    id: dynamic(({ seq }) => `Book-${seq}`),
    name: 'Book',
  },
});
const book = await BookFactory.build({
  name: dynamic(({ seq }) => `Book-${seq}`),
});

After

const BookFactory = defineBookFactory({
  defaultFields: (({ seq }) => ({
    id: `Book-${seq}`,
    name: 'Book',
  })),
});
const book = await BookFactory.build(({ seq }) => ({
  name: `Book-${seq}`,
}));

Case. 2: Use get for Dependent Fields

Before

const AuthorFactory = defineAuthorFactory({
  defaultFields: {
    name: 'mikamikomata',
    email: dynamic(async ({ get }) => `${(await get('name')) ?? 'defaultName'}@yuyushiki.net`),
  },
});

After

const AuthorFactory = defineAuthorFactory({
  defaultFields: (({ seq }) => {
    const name = 'mikamikomata';
    return {
      name,
      email: `${name}@yuyushiki.net`,
    };
  }),
});

Case. 3: Use get for Transient Fields (depend: #73)

Before

const AuthorFactory = defineAuthorFactory.withTransientFields({
  bookCount: 0,
})({
  defaultFields: {
    books: dynamic(async ({ get }) => {
      const bookCount = (await get('bookCount')) ?? 0;
      return BookFactory.buildList(bookCount);
    }),
  },
});

After

const AuthorFactory = defineAuthorFactory.withTransientFields({
  bookCount: 0,
})({
  defaultFields: async ({ transientFields: { bookCount } }) => ({
    books: await BookFactory.buildList(bookCount),
  }),
});

Breaking Changes

• Remove get function
• Remove dynamic utility

[YellowKirby]

Please let me know if this should be a separate issue, but with the proposed changes: could the factories (maybe optionally) become synchronous? Looking at one example, since there's nothing async involved in defineXFactory I would assume that the value generated from .build() could also be synchronous:

const AuthorFactory = defineAuthorFactory({
  defaultFields: (({ seq }) => {
    const name = 'mikamikomata';
    return {
      name,
      email: `${name}@yuyushiki.net`,
    };
  }),
});

That might make it easier to reuse the factories in more places, e.g.: Storybook Stories where the args are declared synchronously.

[mizdra]

@YellowKirby Thanks for your interest in this issue.

could the factories (maybe optionally) become synchronous?

What does factories mean? Do you mean AuthorFactory? Or do you mean .build() method?

[YellowKirby]

What does factories mean? Do you mean AuthorFactory? Or do you mean .build() method?

Sorry, I meant the .build() (and .buildList()) method

[mizdra]

OK.

However, making the build method synchronous is outside the scope of this issue. In this issue, the build method is asynchronous.

I understand the need for a synchronous build method in an environment where top-level await is not available. I have considered implementing that functionality in the past. But I gave up. I did not want to complicate the internal code.

Therefore, I recommend migrating to an ESM that allows for top-level await. Recently many tools support it these days. Storybook also support it (https://github.com/storybookjs/storybook/issues/15129).

[YellowKirby]

Okie dokie! That sounds reasonable, thank you! I think the top-level await will cover what I'm going for in Storybook, thanks for the link :)