react-docgen issues related to flow upgrade

A couple of issues found with recent flow changes, documented by @oliviertassinari and consolidated here.

I’ll be working these issues into PR #9203

• react-docgen doesn’t mark defaulted properties as optional (PR)
• classes missing in some components (needed for docs, not sure if flow needs it)
• theme added to components wrapped in withStyles
• casts inside defaultProps unexpectedly show in docs

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From: https://github.com/callemall/material-ui/pull/9212#issuecomment-345435325

@rosskevin Some broken things I have noticed introduced with #8983. I don’t think that we should put flow interest on top of API ones. Way more people read the API documentation than uses flow.

• We mark properties required while they are not.

-| component | ElementType | 'div' | The component used for the root node. Either a string to use a DOM element or a component. |
+| <span style="color: #31a148">component *</span> | ElementType | 'div' | The component used for the root node. Either a string to use a DOM element or a component. |

• The classes property is missing in some components.

-| classes | Object |  | Useful to extend the style applied to components. |
+| classes | Object |  |  |

• A theme property has been added to all the components.

+| theme | Object |  |  |

From: https://github.com/callemall/material-ui/pull/9203#issuecomment-345377494

A sample of the API diff it’s introducing:

 | Name | Type | Default | Description |
 |:-----|:-----|:--------|:------------|
 | classes | Object |  | Useful to extend the style applied to components. |
-| <span style="color: #31a148">component *</span> | ElementType | 'div' | The component used for the root node. Either a string to use a DOM element or a component. |
+| <span style="color: #31a148">component *</span> | ElementType | 'div': ElementType | The component used for the root node. Either a string to use a DOM element or a component. |

I’m wondering if we can avoid 'div': ElementType. Any idea?

[rosskevin]

I just submitted react-docgen PR https://github.com/reactjs/react-docgen/pull/231

It solves required/optional and flow type casts.

[rosskevin]

@rsolomon if you can PR the change to react-flow-types that would be most helpful. I’ve almost got all the docs changes here wrapped up. Still one bug on my docgen PR for a good pass on material-ui codebase.