Optional values get appended undefined in Addon-docs prop table when using typescript

Describe the bug When using addon:docs prop table for React tsx components optional props marked with ? in typescript get appended undefined in the table.

To Reproduce

1. Follow this guide
2. Run yarn storybook and see the result.

Expected behavior Props marked as optional don’t need the undefined.

System: System: OS: Linux 5.0 Ubuntu 18.04.3 LTS (Bionic Beaver) CPU: (8) x64 Intel® Core™ i7-8550U CPU @ 1.80GHz Binaries: Node: 10.18.0 - /usr/bin/node Yarn: 1.21.1 - /usr/bin/yarn npm: 6.13.4 - /usr/bin/npm Browsers: Chrome: 79.0.3945.88 Firefox: 71.0 npmPackages: @storybook/cli: ^5.3.0 => 5.3.0

[MerlinMason]

@shilman this was v6.4.8

[vimtor]

I think is both correct and redundant. Maybe more redundant than correct since when you add more props you get something like this.

Besides looking buggy is pretty useless because you don’t need to know that undefined is an option since you will never pass it to a prop. I mean, you will never do something like this:

<Button color={undefined} />

That being said, a way to filter the props would be nice however, both the rows that are being displayed and the contents.