feat(testlab): improve typings for toJSON() helper

[bajtos]

While working on #2634, I discovered that findOne returns T | null and this type cannot be passed to toJSON helper, because there is no overload accepting such type.

This pull requests improves the type definitions to let the compiler understand toJSON's behavior for commonly used union types like object | null or unknown[] | null.

Checklist

👉 Read and sign the CLA (Contributor License Agreement) 👈

• npm test passes on your machine
• New tests added or existing tests modified to cover all changes
• Code conforms with the style guide
• API Documentation in code was updated
• Documentation in /docs/site was updated
• Affected artifact templates in packages/cli were updated
• Affected example projects in examples/* were updated

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[hacksparrow]

Why use Math.random()?

[hacksparrow]

Wouldn't this always yield {}?

[raymondfeng]

The Math.random() function returns a floating-point, pseudo-random number in the range 0–1 (inclusive of 0, but not 1) with approximately uniform distribution over that range

I think Math.random() ? returns true in most cases.

[hacksparrow]

Yes, so the behavior of input = null will rarely get tested.

[raymondfeng]

Please extract Math.random() ? to a helper function, such as: randomChoice(...values: any[]): any

[raymondfeng]

For example:

function randomChoice(...values: any[]): any {
  if (!values.length) return undefined;
  const index = Math.floor(Math.random() * values.length);
  return values[index];
}

[bajtos]

Thank you @raymondfeng and @hacksparrow for your comments. I think I really need to improve the tests to make it more clear what is going on and what is being tested. In the tests, I don't really care about the actual value being converted via toJSON, because the implementation is always the same. What I need: compile-time checks.

[bajtos]

The main problem is that from what I can tell by observing type hints offered by VSCode, the following statement is optimized by TypeScript and a simpler type is used instead.

const input: object | null = {};
const output = toJSON(input);
// VSCode shows the following hint:
// (alias) toJSON(value: object): object (+14 overloads)
// import toJSON

Compare to my current version:

const input: object | null = Math.random() ? {} : null;
const output = toJSON(input);
// VSCode shows the following hint:
// (alias) toJSON(value: object | null): object | null (+14 overloads)
// import toJSON

[bajtos]

@raymondfeng @hacksparrow updated, LGTY now?

[hacksparrow]

LGTM if it's just for compile-time TS checks.