Avoid type assertions in update.ts

[grumd]

Hi.

I've looked at your source code and noticed that you're heavily using type assertions, as well as such code smells as "as any".

I want to use this pull request as an encouragement and example to show that type hacks are unnecessary in your codebase and you can do better. If you want to call your library "type-safe" please make sure your internal code is type-safe first and foremost.

Unfortunately I don't have enough time to fully refactor all of your code, so only took liberty of doing it in a couple of files as a proof of concept.

Cheers.

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[grumd]

Note: you may want to change your usages of <T> to <T extends object> for the entity type. Doing keyof T when T is not always an object can be troublesome from the type safety standpoint.

[grumd]

This is questionable however. What is the expected behaviour when a value in diff is null or undefined?

[froehlichA]

Expected is that the property value of the item should then be updated with null/undefined.

interface User {
  id: string;
  name: string;
  age?: number;
}

const aliceId = await insert(userTable, { id: uuid(), name: 'Alice', age: 30 });
await update(userTable, { id: aliceId, age: undefined });

const alice = await one(userTable, { id: aliceId });
expect(alice).toStrictEqual({ id: aliceId, name: 'Alice', age: undefined });

[grumd]

For that to work the user will have to have exactOptionalPropertyTypes enabled in their tsconfig (otherwise this happens), but yes, gotcha.

I've updated the pull request to allow for undefined and null when T allows for it. Took some time to do it type-safely though, wasn't easy.

[froehlichA]

Huh, thanks for the link, didn't know that could happen.

[froehlichA]

Thanks a lot for your contribution :)

Developing BlinkDB, I wanted to focus on type-safety for the user first. I know that internally, the code isn't as type-safe as it could be, but I hope to remedy that in time.

[froehlichA]

I'll create a task on the board about telling users in the docs that they should set this TSconfig option.