fix plugin api

CHANGELOG.md

@@ -29,6 +29,7 @@ See [CHANGELOG - 6to5](CHANGELOG-6to5.md) for the pre-4.0.0 version changelog.
   * Add `jsxPragma` option.
   * Automatically generate CLI options based on internal API options.
   * Add support for `.babelrc` on absolute paths.
+  * Plugin API!
  * **Internal**
   * Export `options` in browser API.
   * Rewritten parser.

src/babel/transformation/file/index.js

@@ -6,7 +6,6 @@ import isFunction from "lodash/lang/isFunction";
 import isAbsolute from "path-is-absolute";
 import resolveRc from "../../tools/resolve-rc";
 import sourceMap from "source-map";
-import Transformer from "../transformer";
 import transform from "./../index";
 import generate from "../../generation";
 import defaults from "lodash/object/defaults";
@@ -177,7 +176,7 @@ export default class File {
   buildTransformers() {
     var file = this;
 
-    var transformers = {};
+    var transformers = this.transformers = {};
 
     var secondaryStack = [];
     var stack = [];
@@ -202,14 +201,13 @@ export default class File {
     // init plugins!
     var beforePlugins = [];
     var afterPlugins = [];
-    for (var i = 0; i < file.opts.plugins; i++) {
-      this.addPlugin(file.opts.plugins[i]);
+    for (var i = 0; i < file.opts.plugins.length; i++) {
+      this.addPlugin(file.opts.plugins[i], beforePlugins, afterPlugins);
     }
     stack = beforePlugins.concat(stack, afterPlugins);
 
     // register
     this.transformerStack = stack.concat(secondaryStack);
-    this.transformers = transformers;
   }
 
   getModuleFormatter(type: string) {
@@ -258,21 +256,17 @@ export default class File {
       throw new TypeError(`Plugin ${JSON.stringify(name)} has an illegal position of ${JSON.stringify(position)}`);
     }
 
-    // validate Transformer instance
-    if (!(plugin instanceof Transformer)) {
-      if (plugin && plugin.constructor.name === "Transformer") {
-        throw new TypeError(`Plugin ${JSON.stringify(name)} exported a Transformer instance but it resolved to a different version of Babel`);
-      } else {
-        throw new TypeError(`Plugin ${JSON.stringify(name)} didn't export default a Transformer instance`);
-      }
-    }
-
     // validate transformer key
     var key = plugin.key;
     if (this.transformers[key]) {
       throw new ReferenceError(`The key for plugin ${JSON.stringify(name)} of ${key} collides with an existing plugin`);
     }
 
+    // validate Transformer instance
+    if (!plugin.buildPass || plugin.constructor.name !== "Transformer") {
+      throw new TypeError(`Plugin ${JSON.stringify(name)} didn't export default a Transformer instance`);
+    }
+
     // build!
     var pass = this.transformers[key] = plugin.buildPass(this);
     if (pass.canTransform()) {

src/babel/transformation/transformer.js

@@ -9,7 +9,7 @@ import each from "lodash/collection/each";
 
 /**
  * This is the class responsible for normalising a transformers handlers
- * as well as constructing a `TransformerPass` that is repsonsible for
+ * as well as constructing a `TransformerPass` that is responsible for
  * actually running the transformer over the provided `File`.
  */
 
@@ -69,6 +69,11 @@ export default class Transformer {
   }
 
   buildPass(file: File): TransformerPass {
+    // validate Transformer instance
+    if (!(file instanceof File)) {
+      throw new TypeError(`Transformer ${this.key} is resolving to a different Babel version to what is doing the actual transformation...`);
+    }
+
     return new TransformerPass(file, this);
   }
 }