parse default values in immediately destructured props

[michelengelen]

We recently had the problem, that with the following component setup there were no defaultValues exported from the docgen:

import {
  PROPERTY1_DEFAULT,
  PROPERTY2_DEFAULT,
  PROPERTY3_DEFAULT
} from './SampleComponent.constants.ts';

const PROPERTY4_DEFAULT = "this is a string";
const PROPERTY5_DEFAULT = true;

type Property1Type = 'hello' | 'world';

type Props = {
  /** prop1 description */
  prop1?: Property1Type;
  /** prop2 description */
  prop2?: 'goodbye' | 'farewell';
  /** prop3 description */
  prop3?: number;
  /** prop4 description */
  prop4?: string;
  /** prop5 description */
  prop5?: boolean;
};

/** SampleComponent description */
const SampleComponent: React.FC<Props> = ({
  prop1 = PROPERTY1_DEFAULT,
  prop2 = PROPERTY2_DEFAULT,
  prop3 = PROPERTY3_DEFAULT,
  prop4 = PROPERTY4_DEFAULT,
  prop5 = PROPERTY5_DEFAULT
}) => ( ... );

export default SampleComponent;

This PR adds the ability to correctly follow initialisation with pre-defined (and/or imported) variables.

[michelengelen]

I do not know if this is the right approach, but I added a new file for testing import statements (and value extraction from those imports).

IMO there should be a separate folder with a constants file where all literal values are assigned to variables/constants and exported, so that those can be used in different tests. For now, and since it is only used by one test, I added it into the __tests__/data folder together with the test.

[pvasek]

@michelengelen Thanks for your PR. It seems perfectly fine to add these constant next to the test. I maybe even prefer this approach as each test is "on it's own" (no meter if it is a single file or multiple files).

[pvasek]

@michelengelen thanks a lot! Published on npm as v1.22.0.