Make plugin loading async

Summary: This diff makes plugin loading async, which we'd need in a browser env (either because we'd use `import()` or we need to fetch the source and than eval it), and deals with all the fallout of that

Reviewed By: timur-valiev

Differential Revision: D32669995

fbshipit-source-id: 73babf38a6757c451b8200c3b320409f127b8b5b

desktop/flipper-ui-browser/src/initializeRenderHost.tsx

@@ -8,6 +8,7 @@
  */
 
 import {FlipperServer, FlipperServerConfig} from 'flipper-common';
+import {getRenderHostInstance} from 'flipper-ui-core';
 
 export function initializeRenderHost(
   flipperServer: FlipperServer,
@@ -62,6 +63,15 @@ export function initializeRenderHost(
       return flipperServerConfig.gatekeepers[gatekeeper] ?? false;
     },
     flipperServer,
+    async requirePlugin(path) {
+      // TODO: use `await import(path)`?
+      const source = await getRenderHostInstance().flipperServer.exec(
+        'plugin-source',
+        path,
+      );
+      // eslint-disable-next-line no-eval
+      return eval(source);
+    },
   };
 }