Generate events with no arguments

Summary:
This diff allows generating native events without any arguments with an event like:

```
{
  name: 'onEnd',
  optional: true,
  bubblingType: 'bubble',
  typeAnnotation: {
    type: 'EventTypeAnnotation',
    // note: no argument key
  },
},
```

See the snapshot updates in the diff for the native code that will be generated �

Reviewed By: shergin

Differential Revision: D15403791

fbshipit-source-id: 925a49bb477eebb234e181df681f0d6b1d4e8cf1

packages/react-native-codegen/src/CodegenSchema.js

@@ -83,7 +83,7 @@ export type EventTypeShape = $ReadOnly<{|
   optional: boolean,
   typeAnnotation: $ReadOnly<{|
     type: 'EventTypeAnnotation',
-    argument: $ReadOnly<{|
+    argument?: $ReadOnly<{|
       type: 'ObjectTypeAnnotation',
       properties: $ReadOnlyArray<ObjectPropertyType>,
     |}>,

packages/react-native-codegen/src/generators/GenerateEventEmitterCpp.js

@@ -55,6 +55,12 @@ void ::_CLASSNAME_::EventEmitter::::_EVENT_NAME_::(::_STRUCT_NAME_:: event) cons
 }
 `.trim();
 
+const basicComponentTemplate = `
+void ::_CLASSNAME_::EventEmitter::::_EVENT_NAME_::() const {
+  dispatchEvent("::_DISPATCH_EVENT_NAME_::");
+}
+`.trim();
+
 function generateSetter(variableName, propertyName, propertyParts) {
   const trailingPeriod = propertyParts.length === 0 ? '' : '.';
   const eventChain = `event.${propertyParts.join(
@@ -106,16 +112,6 @@ function generateSetters(
 }
 
 function generateEvent(componentName: string, event): string {
-  const implementation = `
-    auto payload = jsi::Object(runtime);
-    ${generateSetters('payload', event.typeAnnotation.argument.properties, [])}
-    return payload;
-  `.trim();
-
-  if (!event.name.startsWith('on')) {
-    throw new Error('Expected the event name to start with `on`');
-  }
-
   // This is a gross hack necessary because native code is sending
   // events named things like topChange to JS which is then converted back to
   // call the onChange prop. We should be consistent throughout the system.
@@ -126,15 +122,32 @@ function generateEvent(componentName: string, event): string {
     3,
   )}`;
 
-  return componentTemplate
+  if (event.typeAnnotation.argument) {
+    const implementation = `
+    auto payload = jsi::Object(runtime);
+    ${generateSetters('payload', event.typeAnnotation.argument.properties, [])}
+    return payload;
+  `.trim();
+
+    if (!event.name.startsWith('on')) {
+      throw new Error('Expected the event name to start with `on`');
+    }
+
+    return componentTemplate
+      .replace(/::_CLASSNAME_::/g, componentName)
+      .replace(/::_EVENT_NAME_::/g, event.name)
+      .replace(/::_DISPATCH_EVENT_NAME_::/g, dispatchEventName)
+      .replace(
+        '::_STRUCT_NAME_::',
+        generateStructName(componentName, [event.name]),
+      )
+      .replace('::_IMPLEMENTATION_::', implementation);
+  }
+
+  return basicComponentTemplate
     .replace(/::_CLASSNAME_::/g, componentName)
     .replace(/::_EVENT_NAME_::/g, event.name)
-    .replace(/::_DISPATCH_EVENT_NAME_::/g, dispatchEventName)
-    .replace(
-      '::_STRUCT_NAME_::',
-      generateStructName(componentName, [event.name]),
-    )
-    .replace('::_IMPLEMENTATION_::', implementation);
+    .replace(/::_DISPATCH_EVENT_NAME_::/g, dispatchEventName);
 }
 
 module.exports = {

packages/react-native-codegen/src/generators/GenerateEventEmitterH.js

@@ -146,21 +146,27 @@ function generateStructs(componentName: string, component): string {
   const structs: StructsMap = new Map();
 
   component.events.forEach(event => {
-    generateStruct(
-      structs,
-      componentName,
-      [event.name],
-      event.typeAnnotation.argument.properties,
-    );
+    if (event.typeAnnotation.argument) {
+      generateStruct(
+        structs,
+        componentName,
+        [event.name],
+        event.typeAnnotation.argument.properties,
+      );
+    }
   });
 
   return Array.from(structs.values()).join('\n\n');
 }
 
 function generateEvent(componentName: string, event: EventTypeShape): string {
-  const structName = generateStructName(componentName, [event.name]);
+  if (event.typeAnnotation.argument) {
+    const structName = generateStructName(componentName, [event.name]);
 
-  return `void ${event.name}(${structName} value) const;`;
+    return `void ${event.name}(${structName} value) const;`;
+  }
+
+  return `void ${event.name}() const;`;
 }
 function generateEvents(componentName: string, component): string {
   return component.events

packages/react-native-codegen/src/generators/__test_fixtures__/fixtures.js

@@ -560,6 +560,14 @@ const EVENT_PROPS: SchemaType = {
                 },
               },
             },
+            {
+              name: 'onEnd',
+              optional: true,
+              bubblingType: 'bubble',
+              typeAnnotation: {
+                type: 'EventTypeAnnotation',
+              },
+            },
           ],
           props: [
             {

packages/react-native-codegen/src/generators/__tests__/__snapshots__/GenerateEventEmitterCpp-test.js.snap

@@ -165,6 +165,9 @@ void EventsNativeComponentEventEmitter::onEventDirect(EventsNativeComponentOnEve
     return payload;
   });
 }
+void EventsNativeComponentEventEmitter::onEnd() const {
+  dispatchEvent(\\"end\\");
+}
 
 } // namespace react
 } // namespace facebook

packages/react-native-codegen/src/generators/__tests__/__snapshots__/GenerateEventEmitterH-test.js.snap

@@ -173,6 +173,8 @@ class EventsNativeComponentEventEmitter : public ViewEventEmitter {
   void onChange(EventsNativeComponentOnChangeStruct value) const;
 
   void onEventDirect(EventsNativeComponentOnEventDirectStruct value) const;
+
+  void onEnd() const;
 };
 
 } // namespace react

packages/react-native-codegen/src/generators/__tests__/__snapshots__/GenerateViewConfigJs-test.js.snap

@@ -285,6 +285,13 @@ const EventsNativeComponentViewConfig = {
         bubbled: 'onChange',
       },
     },
+
+    topEnd: {
+      phasedRegistrationNames: {
+        captured: 'onEndCapture',
+        bubbled: 'onEnd',
+      },
+    },
   },
 
   directEventTypes: {
@@ -300,6 +307,7 @@ const EventsNativeComponentViewConfig = {
     disabled: true,
     onChange: true,
     onEventDirect: true,
+    onEnd: true,
   },
 };