abstract plugin initialisation to a plugin manager

src/babel/messages.js

@@ -26,7 +26,15 @@ export const MESSAGES = {
   traverseNeedsParent: "Must pass a scope and parentPath unless traversing a Program/File got a $1 node",
   traverseVerifyRootFunction: "You passed `traverse()` a function when it expected a visitor object, are you sure you didn't mean `{ enter: Function }`?",
   traverseVerifyVisitorFunction: "Hey! You passed \`traverse()\` a visitor object with the key $1 that's a straight up `Function` instead of `{ enter: Function }`. You need to normalise it with `traverse.explode(visitor)`.",
-  traverseVerifyVisitorProperty: "You passed `traverse()` a visitor object with the property $1 that has the invalid property $2"
+  traverseVerifyVisitorProperty: "You passed `traverse()` a visitor object with the property $1 that has the invalid property $2",
+
+  pluginIllegalKind: "Illegal kind $1 for plugin $2",
+  pluginIllegalPosition: "Illegal position $1 for plugin $2",
+  pluginKeyCollision: "The plugin $1 collides with another of the same name",
+  pluginNotTransformer: "The plugin $1 didn't export a Transformer instance",
+  pluginUnknown: "Unknown plugin $1",
+
+  transformerNotFile: "Transformer $1 is resolving to a different Babel version to what is doing the actual transformation..."
 };
 
 export function get(key: String, ...args) {

src/babel/transformation/file/index.js

@@ -1,5 +1,6 @@
 import convertSourceMap from "convert-source-map";
 import * as optionParsers from "./option-parsers";
+import PluginManager from "./plugin-manager";
 import shebangRegex from "shebang-regex";
 import TraversalPath from "../../traversal/path";
 import isFunction from "lodash/lang/isFunction";
@@ -18,6 +19,7 @@ import Scope from "../../traversal/scope";
 import slash from "slash";
 import clone from "lodash/lang/clone";
 import * as util from  "../../util";
+import * as api from  "../../api/node";
 import path from "path";
 import each from "lodash/collection/each";
 import * as t from "../../types";
@@ -217,8 +219,9 @@ export default class File {
     // init plugins!
     var beforePlugins = [];
     var afterPlugins = [];
+    var pluginManager = new PluginManager(this.transformers, beforePlugins, afterPlugins);
     for (var i = 0; i < file.opts.plugins.length; i++) {
-      this.addPlugin(file.opts.plugins[i], beforePlugins, afterPlugins);
+      pluginManager.add(file.opts.plugins[i]);
     }
     stack = beforePlugins.concat(stack, afterPlugins);
 
@@ -241,60 +244,6 @@ export default class File {
     return new ModuleFormatter(this);
   }
 
-  addPlugin(name, before, after) {
-    var position = "before";
-    var plugin;
-
-    if (name) {
-      if (typeof name === "object" && name.transformer) {
-        plugin = name.transformer;
-        position = name.position || position;
-      } else if (typeof name === "string") {
-        // this is a plugin in the form of "foobar" or "foobar:after"
-        // where the optional colon is the delimiter for plugin position in the transformer stack
-
-        [name, position = "before"] = name.split(":");
-
-        var loc = util.resolveRelative(name) || util.resolveRelative(`babel-plugin-${name}`);
-        if (loc) {
-          plugin = require(loc)
-        } else {
-          throw new ReferenceError(`Unknown plugin ${JSON.stringify(name)}`);
-        }
-      } else {
-        // not a string so we'll just assume that it's a direct Transformer instance, if not then
-        // the checks later on will complain
-        plugin = name;
-      }
-    } else {
-      throw new TypeError(`Ilegal kind ${typeof name} for plugin name ${JSON.stringify(name)}`);
-    }
-
-    // validate position
-    if (position !== "before" && position !== "after") {
-      throw new TypeError(`Plugin ${JSON.stringify(name)} has an illegal position of ${JSON.stringify(position)}`);
-    }
-
-    // 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 a default Transformer instance`);
-    }
-
-    // build!
-    var pass = this.transformers[key] = plugin.buildPass(this);
-    if (pass.canTransform()) {
-      var stack = before;
-      if (position === "after") stack = after;
-      stack.push(pass);
-    }
-  }
-
   parseInputSourceMap(code: string) {
     var opts = this.opts;
 

src/babel/transformation/file/plugin-manager.js

@@ -0,0 +1,99 @@
+import * as messages from "../../messages";
+
+export default class PluginManager {
+  static memoisedPlugins = [];
+
+  static memoisePluginContainer(fn) {
+    for (var i = 0; i < PluginManager.memoisedPlugins.length; i++) {
+      var plugin = PluginManager.memoisedPlugins[i];
+      if (plugin.container === fn) return plugin.transformer;
+    }
+
+    var transformer = fn(node);
+    PluginManager.memoisedPlugins.push({
+      container: fn,
+      transformer: transformer
+    });
+    return transformer;
+  }
+
+  constructor(transformers, before, after) {
+    this.transformers = transformers;
+    this.before       = before;
+    this.after        = after;
+  }
+
+  subnormaliseString(name) {
+    // this is a plugin in the form of "foobar" or "foobar:after"
+    // where the optional colon is the delimiter for plugin position in the transformer stack
+
+    var [name, position] = name.split(":");
+
+    var loc = util.resolveRelative(name) || util.resolveRelative(`babel-plugin-${name}`);
+    if (loc) {
+      return {
+        position: position,
+        plugin:   require(loc)
+      };
+    } else {
+      throw new ReferenceError(messages.get("pluginUnknown", name));
+    }
+  }
+
+  validate(plugin) {
+    // validate transformer key
+    var key = plugin.key;
+    if (this.transformers[key]) {
+      throw new ReferenceError(messages.get("pluginKeyCollision", key));
+    }
+
+    // validate Transformer instance
+    if (!plugin.buildPass || plugin.constructor.name !== "Transformer") {
+      throw new TypeError(messages.get("pluginNotTransformer", name));
+    }
+  }
+
+  add(name) {
+    var position;
+    var plugin;
+
+    if (name) {
+      if (typeof name === "object" && name.transformer) {
+        ({ plugin: name, position } = name);
+      } else if (typeof name !== "string") {
+        // not a string so we'll just assume that it's a direct Transformer instance, if not then
+        // the checks later on will complain
+        plugin = name;
+      }
+
+      if (typeof name === "string") {
+        ({ plugin, position } = this.subnormaliseString(name));
+      }
+    } else {
+      throw new TypeError(messages.get("pluginIllegalKind", typeof name, name));
+    }
+
+    // default position
+    position = position || "before";
+
+    // validate position
+    if (position !== "before" && position !== "after") {
+      throw new TypeError(messages.get("pluginIllegalPosition", position, name));
+    }
+
+    // allow plugin containers to be specified so they don't have to manually require
+    if (typeof plugin === "function") {
+      plugin = PluginManager.memoisePluginContainer(plugin);
+    }
+
+    //
+    this.validate(plugin);
+
+    // build!
+    var pass = this.transformers[key] = plugin.buildPass(this);
+    if (pass.canTransform()) {
+      var stack = position === "before" ? this.before : this.after;
+      stack.push(pass);
+    }
+  }
+}

src/babel/transformation/transformer.js

@@ -87,7 +87,7 @@ 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...`);
+      throw new TypeError(messages.get("transformerNotFile", this.key));
     }
 
     return new TransformerPass(file, this);