Fix babel-standalone for realz (#6137)

* Fix babel-standalone

* Fix infinite loop in Makefile (oops)

* Override Node.js module resolution to handle babel-core

packages/babel-standalone/src/gulpTasks.js

@@ -4,8 +4,14 @@
  * compilation of all the JavaScript files. This is because it targets web
  * browsers, so more transforms are needed than the regular Babel builds that
  * only target Node.js.
+ *
+ * The tasks in this file are designed to be reusable, so that they can be used
+ * to make standalone builds of other Babel plugins/presets (such as babel-minify)
  */
 
+// Must run first
+require("./overrideModuleResolution")();
+
 const pump = require("pump");
 const rename = require("gulp-rename");
 const RootMostResolvePlugin = require("webpack-dependency-suite").RootMostResolvePlugin;
@@ -100,24 +106,27 @@ function webpackBuild(filename, libraryName, version) {
   });*/
 }
 
-function registerGulpTasks(gulp) {
-  gulp.task("build-babel-standalone", ["build"], cb => {
+function registerBabelStandaloneTask(gulp, name, exportName, path, version) {
+  gulp.task("build-" + name + "-standalone", cb => {
     pump(
       [
-        gulp.src(__dirname + "/index.js"),
+        gulp.src(path + "/src/index.js"),
         webpackBuild(
-          "babel.js",
-          "Babel",
-          require(__dirname + "/../package.json").version
+          name + ".js",
+          exportName,
+          version
         ),
-        gulp.dest(__dirname + "/../"),
+        gulp.dest(path),
         uglify(),
         rename({ extname: ".min.js" }),
-        gulp.dest(__dirname + "/../"),
+        gulp.dest(path),
       ],
       cb
     );
   });
 }
 
-module.exports = registerGulpTasks;
+module.exports = {
+  webpackBuild: webpackBuild,
+  registerBabelStandaloneTask: registerBabelStandaloneTask,
+}

packages/babel-standalone/src/overrideModuleResolution.js

@@ -0,0 +1,24 @@
+/**
+ * babel-loader causes problems as it's not part of the monorepo. It pulls in
+ * an older version of babel-core (the version referenced by the root
+ * package.json), rather than the version of babel-core that's in the repo. The
+ * only way to solve this without moving babel-loader into the monorepo is to
+ * override Node's module resolution algorithm to specify a custom resolver for
+ * babel-core to *force* it to use our version.
+ *
+ * Here be dragons.
+ */
+
+const Module = require("module");
+
+module.exports = function overrideModuleResolution() {
+  const originalLoader = Module._load.bind(Module);
+
+  Module._load = function babelStandaloneLoader(request, parent, isMain) {
+    // Redirect babel-core to version in the repo.
+    if (request === "babel-core") {
+      request = __dirname + "/../../babel-core";
+    }
+    return originalLoader(request, parent, isMain);
+  };
+};