Flow type event plugins

[flarnie]

Type SimpleEventPlugin and TapEventPlugin

• Fills in the 'any' holes that were left in DispatchConfig type and the
  type annotations in EventPluginRegistry.
• Adds polymorphic PluginModule type and related types
• Uses hack to support indexable properties on 'Touch' type in
  TapEventPlugin

The issue in TapEventPlugin is that the code is accessing one of four
possible properties on the 'Touch' type native event using the bracket
accessor. Classes in Flow don't support using the bracket accessor,
unless you use a declaration and the syntax [key: Type]: Type.1 The
downside of using that here is that we create a global type, which we
may not need in other files.

Other options:

• Use looser typing or a '@fixme' comment and open an issue with Flow to
  support indexing on regular classes.
• Rewrite TapEventPlugin to not use the bracket accessor on 'Touch'. I
  thought the current implementation was elegant and didn't want to
  change it. But we could do something like this:

 if (nativeEvent.pageX || nativeEvent.pageY) {
   return axis.page === 'pageX' ? nativeEvent.pageX : nativeEvent.pageY;
 } else {
   var clientAxis = axis.client === 'clientX' ? nativeEvent.clientX : nativeEvent.clientY;
   return nativeEvent[axis.client] + ViewportMetrics[axis.envScroll];
 }

[vjeux]

I've been adding a space between {} but looks like the convention on www is not to (15k vs 500). Good thing you're helping on this effort so that I don't start diverging by mistake :p

[coveralls]

Coverage increased (+0.003%) to 87.192% when pulling 4a0b39b on flarnie:flowTypeEventPlugins into 0c77b2f on facebook:master.

[vjeux]

Sounds like a good workaround, thanks for evaluating all the possible solutions :)

[vjeux]

Looks really good thanks!

[vjeux]

Thanks for the comments. For this pull request:

1. Let's fix the following in this pull request:

let pluginModule;

2. Quickly evaluate if phasedRegistrationNames? is indeed nullable in practice and update/leave this as is.

Then we can do the rest of comments in follow up pull requests

[camspiers]

null | ReactSyntheticEvent -> ?ReactSyntheticEvent

[camspiers]

Ignore me, I guess ?ReactSyntheticEvent would also include undefined and I guess you aren't wanting that.

[flarnie]

Thanks! I would have said the same thing too, except @aweary pointed out the benefits of null | <Type> to me in a different PR. Based on this post by sebmarkbage.

[vjeux]

shipit :)

[vjeux]

Unfortunately, we have a bug with Travis where it doesn't properly run flow and this commit triggers flow errors :( https://www.facebook.com/groups/2003630259862046/permalink/2095244497367288/

I'm trying to look into it right now

src/renderers/dom/client/eventPlugins/TapEventPlugin.js:112
112: var eventTypes: DispatchConfig = {
                     ^^^^^^^^^^^^^^ property `dependencies`. Property not found in
112: var eventTypes: DispatchConfig = {
                                      ^ object literal

src/renderers/dom/client/eventPlugins/TapEventPlugin.js:156
156:         eventTypes.touchTap,
                        ^^^^^^^^ property `touchTap`. Property not found in
156:         eventTypes.touchTap,
             ^^^^^^^^^^ object type

src/renderers/shared/stack/event/PluginModuleType.js:21
 21: type EventTypes = {[key: string]: DispatchConfig};
                                       ^^^^^^^^^^^^^^ property `dependencies`. Property not found in
 21:   phasedRegistrationNames?: {
                                 ^ object type. See: src/renderers/shared/stack/event/ReactSyntheticEventType.js:21

src/renderers/shared/stack/event/PluginModuleType.js:21
 21: type EventTypes = {[key: string]: DispatchConfig};
                                       ^^^^^^^^^^^^^^ property `phasedRegistrationNames`. Property not found in
 21:   phasedRegistrationNames?: {
                                 ^ object type. See: src/renderers/shared/stack/event/ReactSyntheticEventType.js:21

src/renderers/shared/stack/event/PluginModuleType.js:21
 21: type EventTypes = {[key: string]: DispatchConfig};
                                       ^^^^^^^^^^^^^^ property `registrationName`. Property not found in
 21:   phasedRegistrationNames?: {
                                 ^ object type. See: src/renderers/shared/stack/event/ReactSyntheticEventType.js:21

src/renderers/shared/stack/event/ReactSyntheticEventType.js:20
 20:   dependencies: Array<string>,
                     ^^^^^^^^^^^^^ array type. This type is incompatible with
 21: type EventTypes = {[key: string]: DispatchConfig};
                                       ^^^^^^^^^^^^^^ object type. See: src/renderers/shared/stack/event/PluginModuleType.js:21

src/renderers/shared/stack/event/ReactSyntheticEventType.js:21
 21:   phasedRegistrationNames?: {
                                 ^ undefined. This type is incompatible with
 21: type EventTypes = {[key: string]: DispatchConfig};
                                       ^^^^^^^^^^^^^^ object type. See: src/renderers/shared/stack/event/PluginModuleType.js:21

src/renderers/shared/stack/event/ReactSyntheticEventType.js:25
 25:   registrationName?: string,
                          ^^^^^^ string. This type is incompatible with
 21: type EventTypes = {[key: string]: DispatchConfig};
                                       ^^^^^^^^^^^^^^ object type. See: src/renderers/shared/stack/event/PluginModuleType.js:21

src/renderers/shared/stack/event/ReactSyntheticEventType.js:25
 25:   registrationName?: string,
                          ^^^^^^ undefined. This type is incompatible with
 21: type EventTypes = {[key: string]: DispatchConfig};
                                       ^^^^^^^^^^^^^^ object type. See: src/renderers/shared/stack/event/PluginModuleType.js:21


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