Override tsc options for plugins

Plugins will sometimes have their own `tsconfig.json`, which will
interfere with the dev server config if configured inappropriately.

This change makes sure `tsc` (and `ts-loader`) always compiles to
`esnext` modules, so we don't get "Uncaught ReferenceError: exports
is not defined" error.

superset-frontend/tsconfig.json

@@ -25,8 +25,10 @@
   "include": [
     "./src/**/*",
     "./spec/**/*",
+    // include the source code of each plugin
     "./node_modules/*superset-ui*/**/src/**/*",
     "./node_modules/*superset-ui*/**/types/**/*",
+    // and the type defs of their dependencies
     "./node_modules/*superset-ui*/**/node_modules/**/*.d.ts"
   ]
 }

superset-frontend/webpack.config.js

@@ -224,6 +224,15 @@ const config = {
               // type checking is done via fork-ts-checker-webpack-plugin
               happyPackMode: true,
               transpileOnly: true,
+              // must override compiler options here, even though we have set
+              // the same options in `tsconfig.json`, because they may still
+              // be overriden by `tsconfig.json` in node_modules subdirectories.
+              compilerOptions: {
+                esModuleInterop: false,
+                importHelpers: false,
+                module: 'esnext',
+                target: 'esnext',
+              },
             },
           },
         ],