[addon-docs] Props component render defaultProps from the last component from the file

[lgraziani2712]

Describe the bug

I have a MDX file that renders the Props for a component from a file with two components. The default value for one of its props has the value from the defaultProps of the last component. If I change the order of them, it changes the default value being rendered.

BTW, I'm using the typescript-preset.

To Reproduce
Steps to reproduce the behavior:

1. Create a tsx files with two named export components and configure a prop with default value for each of them. That prop must have the same name for both of them but different accepted values.
2. Create a mdx story.
3. Import one or both (it doesn't matter) components and render their props.
4. Change the order of the components (in the tsx file).
5. See how the default value changes to the value of the last component.

Expected behavior
To respect the default value for each component.

Screenshots

Code snippets

export interface ElemAProps {
  size?: 'a' | 'b' | 'c' | 'd';
}

export const ElemA: React.SFC<ElemAProps> = ({ size = 'a', children }) => (
  <div className={size}>{children}</div>
);

export interface ElemBProps {
  size?: 'sm' | 'md' | 'lg';
}

export const Paragraph: React.SFC<ElemBProps> = props => (
  <div className={props.size}>{props.children}</div>
);

ElemBProps.defaultProps = { size: 'md' };

System:

  System:
    OS: Linux 4.15 Ubuntu 18.04.3 LTS (Bionic Beaver)
    CPU: (4) x64 Intel(R) Core(TM) i7-4510U CPU @ 2.00GHz
  Binaries:
    Node: 10.16.0 - ~/.nvm/versions/node/v10.16.0/bin/node
    Yarn: 1.19.1 - /usr/bin/yarn
    npm: 6.9.0 - ~/.nvm/versions/node/v10.16.0/bin/npm
  Browsers:
    Chrome: 78.0.3904.87
    Firefox: 71.0b7
  npmPackages:
    @storybook/addon-actions: 5.2.5 => 5.2.5 
    @storybook/addon-backgrounds: 5.2.5 => 5.2.5 
    @storybook/addon-docs: 5.2.5 => 5.2.5 
    @storybook/addon-knobs: 5.2.5 => 5.2.5 
    @storybook/preset-typescript: 1.1.0 => 1.1.0 
    @storybook/react: 5.2.5 => 5.2.5 

[stale]

Hi everyone! Seems like there hasn't been much going on in this issue lately. If there are still questions, comments, or bugs, please feel free to continue the discussion. Unfortunately, we don't have time to get to every issue. We are always open to contributions so please send us a pull request if you would like to help. Inactive issues will be closed after 30 days. Thanks!

[shilman]

Repro: 85e4f6d

[shilman]

We’re cleaning house! Storybook has changed a lot since this issue was created and we don’t know if it’s still valid.

Please open a new issue referencing this one if:

• this is still a problem in SB 7.x
• you can provide a consistent reproduction in 7.x (at https://storybook.new/ or per repro docs).