From 78c21a282a10cd3ee3e8335e9e0a95e7dbfd93c2 Mon Sep 17 00:00:00 2001
From: Eric Baer <me@ericbaer.com>
Date: Thu, 1 Sep 2016 08:55:50 -0700
Subject: [PATCH] Implement very basic (but working) functionality (#3)

* Implement very basic (but working) functionality

* Correct PR based on feedback
---
 experimental/babel-preset-env/package.json   |  45 ++--
 experimental/babel-preset-env/src/index.js   | 237 ++++++-------------
 experimental/babel-preset-env/src/plugins.js | 131 ++++++++++
 experimental/babel-preset-env/test/index.js  |  32 +++
 4 files changed, 262 insertions(+), 183 deletions(-)
 create mode 100644 experimental/babel-preset-env/src/plugins.js
 create mode 100644 experimental/babel-preset-env/test/index.js

diff --git a/experimental/babel-preset-env/package.json b/experimental/babel-preset-env/package.json
index 8004ef0a21..ef4e7e6ebd 100644
--- a/experimental/babel-preset-env/package.json
+++ b/experimental/babel-preset-env/package.json
@@ -13,18 +13,16 @@
     "lint": "eslint src test",
     "fix": "eslint src test --fix",
     "ci": "npm run lint && npm run test",
-    "prepublish": "npm run build"
+    "prepublish": "npm run build",
+    "test": "mocha ./test"
   },
   "dependencies": {
-    "babel-plugin-transform-es2015-modules-amd": "^6.8.0",
-    "babel-plugin-transform-es2015-modules-commonjs": "^6.6.0",
-    "babel-plugin-transform-es2015-modules-systemjs": "^6.12.0",
-    "babel-plugin-transform-es2015-modules-umd": "^6.12.0",
-    "babel-plugin-transform-es3-member-expression-literals": "^6.3.13",
-    "babel-plugin-transform-es3-property-literals": "^6.3.13",
-    "babel-plugin-transform-proto-to-assign": "^6.9.0",
-    "babel-plugin-transform-es5-property-mutators": "^6.3.13",
     "babel-plugin-check-es2015-constants": "^6.3.13",
+    "babel-plugin-syntax-trailing-function-commas": "^6.13.0",
+    "babel-plugin-transform-async-to-generator": "^6.8.0",
+    "babel-plugin-transform-class-properties": "^6.11.5",
+    "babel-plugin-transform-decorators-legacy": "^1.3.4",
+    "babel-plugin-transform-do-expressions": "^6.8.0",
     "babel-plugin-transform-es2015-arrow-functions": "^6.3.13",
     "babel-plugin-transform-es2015-block-scoped-functions": "^6.3.13",
     "babel-plugin-transform-es2015-block-scoping": "^6.6.0",
@@ -35,6 +33,10 @@
     "babel-plugin-transform-es2015-for-of": "^6.6.0",
     "babel-plugin-transform-es2015-function-name": "^6.3.13",
     "babel-plugin-transform-es2015-literals": "^6.3.13",
+    "babel-plugin-transform-es2015-modules-amd": "^6.8.0",
+    "babel-plugin-transform-es2015-modules-commonjs": "^6.6.0",
+    "babel-plugin-transform-es2015-modules-systemjs": "^6.12.0",
+    "babel-plugin-transform-es2015-modules-umd": "^6.12.0",
     "babel-plugin-transform-es2015-object-super": "^6.3.13",
     "babel-plugin-transform-es2015-parameters": "^6.6.0",
     "babel-plugin-transform-es2015-shorthand-properties": "^6.3.13",
@@ -43,16 +45,16 @@
     "babel-plugin-transform-es2015-template-literals": "^6.6.0",
     "babel-plugin-transform-es2015-typeof-symbol": "^6.6.0",
     "babel-plugin-transform-es2015-unicode-regex": "^6.3.13",
-    "babel-plugin-transform-regenerator": "^6.6.0",
+    "babel-plugin-transform-es3-member-expression-literals": "^6.3.13",
+    "babel-plugin-transform-es3-property-literals": "^6.3.13",
+    "babel-plugin-transform-es5-property-mutators": "^6.3.13",
     "babel-plugin-transform-exponentiation-operator": "^6.8.0",
-    "babel-plugin-syntax-trailing-function-commas": "^6.13.0",
-    "babel-plugin-transform-async-to-generator": "^6.8.0",
-    "babel-plugin-transform-class-properties": "^6.11.5",
-    "babel-plugin-transform-decorators-legacy": "^1.3.4",
-    "babel-plugin-transform-do-expressions": "^6.8.0",
     "babel-plugin-transform-export-extensions": "^6.8.0",
     "babel-plugin-transform-function-bind": "^6.8.0",
-    "babel-plugin-transform-object-rest-spread": "^6.8.0"
+    "babel-plugin-transform-object-rest-spread": "^6.8.0",
+    "babel-plugin-transform-proto-to-assign": "^6.9.0",
+    "babel-plugin-transform-regenerator": "^6.6.0",
+    "lodash.includes": "^4.3.0"
   },
   "devDependencies": {
     "babel-cli": "^6.11.4",
@@ -61,10 +63,19 @@
     "eslint": "^3.3.1",
     "eslint-config-babel": "^1.0.1",
     "eslint-plugin-babel": "^3.3.0",
-    "eslint-plugin-flow-vars": "^0.5.0"
+    "eslint-plugin-flow-vars": "^0.5.0",
+    "mocha": "^3.0.2"
   },
   "babel": {
     "plugins": [
+      "babel-plugin-transform-es2015-destructuring",
+      "babel-plugin-transform-es2015-function-name",
+      "babel-plugin-transform-es2015-modules-commonjs",
+      "babel-plugin-transform-es2015-parameters",
+      "babel-plugin-transform-es2015-shorthand-properties",
+      "babel-plugin-transform-es2015-spread",
+      "babel-plugin-transform-es2015-sticky-regex",
+      "babel-plugin-transform-es2015-unicode-regex",
       "transform-class-properties",
       "transform-flow-strip-types"
     ]
diff --git a/experimental/babel-preset-env/src/index.js b/experimental/babel-preset-env/src/index.js
index d7c6533265..9c5cf26225 100644
--- a/experimental/babel-preset-env/src/index.js
+++ b/experimental/babel-preset-env/src/index.js
@@ -4,172 +4,14 @@
 // "proto-to-assign",
 // "es5-property-mutators",
 
-export const pluginsList = {
-  // es2015
-  "transform-es2015-arrow-functions": {
-    edge: 13,
-    firefox: 45,
-    chrome: 49,
-    opera: 36,
-  },
-  "transform-es2015-block-scoped-functions": {
-    edge: 11,
-    firefox: 46,
-    chrome: 41,
-    opera: 28,
-  },
-  "transform-es2015-block-scoping": {
-    edge: 11,
-    firefox: 36,
-    chrome: 49,
-    opera: 36,
-  },
-  "transform-es2015-classes": {
-    edge: 13,
-    firefox: 45,
-    chrome: 49,
-    opera: 36,
-  },
-  "transform-es2015-computed-properties": {
-    edge: 12,
-    firefox: 34,
-    chrome: 44,
-    opera: 31
-  },
-  "check-es2015-constants": {
-    edge: 11,
-    firefox: 36,
-    chrome: 49,
-    opera: 36,
-  },
-  "transform-es2015-destructuring": {
-    edge: 14,
-    firefox: Infinity,
-    chrome: 52,
-    opera: 39,
-  },
-  "transform-es2015-for-of": {
-    edge: Infinity,
-    firefox: Infinity,
-    chrome: 51,
-    opera: 38,
-  },
-  "transform-es2015-function-name": {
-    edge: Infinity,
-    firefox: Infinity,
-    chrome: 52,
-    opera: 39,
-  },
-  "transform-es2015-literals": {
-    edge: 12,
-    firefox: 36,
-    chrome: 41,
-    opera: 28
-  },
-  "transform-es2015-object-super": {
-    edge: 13,
-    firefox: 45,
-    chrome: 49,
-    opera: 36,
-  },
-  "transform-es2015-parameters": {
-    edge: 14,
-    firefox: Infinity,
-    chrome: 49,
-    opera: 36,
-  },
-  "transform-es2015-shorthand-properties": {
-    edge: 12,
-    firefox: 33,
-    chrome: 43,
-    opera: 30
-  },
-  "transform-es2015-spread": {
-    edge: 13,
-    firefox: 36,
-    chrome: 46,
-    opera: 33,
-  },
-  "transform-es2015-sticky-regex": {
-    edge: 13,
-    firefox: 31,
-    chrome: 49,
-    opera: 36
-  },
-  "transform-es2015-template-literals": {
-    edge: 13,
-    firefox: 34,
-    chrome: 41,
-    opera: 28,
-  },
-  "transform-es2015-typeof-symbol": {
-    edge: 12,
-    firefox: 36,
-    chrome: 38,
-    opera: 25,
-  },
-  "transform-es2015-unicode-regex": {
-    edge: 12,
-    firefox: 46,
-    chrome: 51,
-    opera: 38,
-  },
-  "transform-regenerator": {
-    edge: 13,
-    firefox: 45,
-    chrome: 49,
-    opera: 36,
-  },
-
-  // es2016
-  "transform-exponentiation-operator": {
-    edge: 14,
-    chrome: 52,
-  },
-
-  // es2017
-  "transform-async-to-generator": {
-    edge: 14,
-  },
-  "syntax-trailing-function-commas": {
-    edge: 14,
-  }
-};
+import includes from "lodash.includes";
+import pluginList from "./plugins.js";
 
 export const plugins = [
   "es3-member-expression-literals",
   "es3-property-literals",
   "proto-to-assign",
-
   "es5-property-mutators",
-
-  // es2015
-  "transform-es2015-arrow-functions",
-  "transform-es2015-block-scoped-functions",
-  "transform-es2015-block-scoping",
-  "transform-es2015-classes",
-  "transform-es2015-computed-properties",
-  "check-es2015-constants",
-  "transform-es2015-destructuring",
-  "transform-es2015-for-of",
-  "transform-es2015-function-name",
-  "transform-es2015-literals",
-  "transform-es2015-object-super",
-  "transform-es2015-parameters",
-  "transform-es2015-shorthand-properties",
-  "transform-es2015-spread",
-  "transform-es2015-sticky-regex",
-  "transform-es2015-template-literals",
-  "transform-es2015-typeof-symbol",
-  "transform-es2015-unicode-regex",
-  "transform-regenerator",
-
-  // es2016
-  "transform-exponentiation-operator",
-
-  // es2017
-  "transform-async-to-generator",
-  "syntax-trailing-function-commas"
 ];
 
 // modules?
@@ -190,12 +32,75 @@ export const stagePlugins = [
   "transform-object-rest-spread",
 ];
 
-export default function(opts) {
-  let stage = 4;
-  if (opts !== undefined){
-    if (opts.stage !== undefined) stage = opts.stage;
-  }
+/**
+ * Determine if a transformation is required
+ * @param  {Object}  supportedEnvironments  An Object containing environment keys and the lowest
+ *                                          supported version as a value
+ * @param  {Object}  plugin                 An Object containing environment keys and the lowest
+ *                                          version the feature was implmented in as a value
+ * @return {Boolean}  Whether or not the transformation is required
+ */
+export const isPluginRequired = (supportedEnvironments, plugin) => {
+  const targetEnvironments = Object.keys(supportedEnvironments);
 
-  if (typeof stage !== "boolean") throw new Error("Preset es2015 'loose' option must be a boolean.");
+  if (targetEnvironments.length === 0) { return true; }
 
+  const isRequiredForEnvironments = targetEnvironments
+    .filter(environemt => {
+      // Feature is not implemented in that environment
+      if (!plugin[environemt]) { return true; }
+
+      const lowestImplementedVersion = plugin[environemt];
+      const lowestTargetedVersion = targetEnvironments[environemt];
+      if (lowestTargetedVersion <= lowestImplementedVersion) { return true; }
+
+      return false;
+    });
+
+  return isRequiredForEnvironments.length > 0 ? true : false;
+};
+
+const getTargets = targetOpts => {
+  return targetOpts || {};
+}
+
+// TODO: Allow specifying plugins as either shortened or full name
+// babel-plugin-transform-es2015-classes
+// transform-es2015-classes
+const getLooseMode = looseOpts => {
+  if (!looseOpts) { return []; }
+  return looseOpts;
+}
+
+// TODO: Allow specifying modules as: Boolean, String or Array of module types
+const getModules = modulesOpts => {
+  if (!modulesOpts) { return []; }
+  return modulesOpts;
+}
+
+export default function(opts) {
+  const looseMode = getLooseMode(opts.loose);
+  const modulesMode = getModules(opts.modules);
+  const targets = getTargets(opts.targets);
+
+  const transformations = Object.keys(pluginList)
+    .filter(pluginName => isPluginRequired(targets, pluginList[pluginName]))
+    .map(pluginName => {
+      return includes(looseMode, pluginName)
+        ? [require(`babel-plugin-${pluginName}`), { loose: true }]
+        : require(`babel-plugin-${pluginName}`);
+    });
+
+  // TODO: Support loose mode
+  const modules = Object.keys(modulesMode)
+    .map(moduleType => {
+      return [require(`babel-plugin-transform-es2015-modules-${moduleType}`)]
+    });
+
+  return {
+    plugins: [
+      ...modules,
+      ...transformations
+    ]
+  }
 }
diff --git a/experimental/babel-preset-env/src/plugins.js b/experimental/babel-preset-env/src/plugins.js
new file mode 100644
index 0000000000..377f8196cf
--- /dev/null
+++ b/experimental/babel-preset-env/src/plugins.js
@@ -0,0 +1,131 @@
+export default {
+  // es2015
+  "transform-es2015-arrow-functions": {
+    edge: 13,
+    firefox: 45,
+    chrome: 49,
+    opera: 36,
+  },
+  "transform-es2015-block-scoped-functions": {
+    edge: 11,
+    firefox: 46,
+    chrome: 41,
+    opera: 28,
+  },
+  "transform-es2015-block-scoping": {
+    edge: 11,
+    firefox: 36,
+    chrome: 49,
+    opera: 36,
+  },
+  "transform-es2015-classes": {
+    edge: 13,
+    firefox: 45,
+    chrome: 49,
+    opera: 36,
+  },
+  "transform-es2015-computed-properties": {
+    edge: 12,
+    firefox: 34,
+    chrome: 44,
+    opera: 31
+  },
+  "check-es2015-constants": {
+    edge: 11,
+    firefox: 36,
+    chrome: 49,
+    opera: 36,
+  },
+  "transform-es2015-destructuring": {
+    edge: 14,
+    firefox: Number.NEGATIVE_INFINITY,
+    chrome: 52,
+    opera: 39,
+  },
+  "transform-es2015-for-of": {
+    edge: Number.NEGATIVE_INFINITY,
+    firefox: Number.NEGATIVE_INFINITY,
+    chrome: 51,
+    opera: 38,
+  },
+  "transform-es2015-function-name": {
+    edge: Number.NEGATIVE_INFINITY,
+    firefox: Number.NEGATIVE_INFINITY,
+    chrome: 52,
+    opera: 39,
+  },
+  "transform-es2015-literals": {
+    edge: 12,
+    firefox: 36,
+    chrome: 41,
+    opera: 28
+  },
+  "transform-es2015-object-super": {
+    edge: 13,
+    firefox: 45,
+    chrome: 49,
+    opera: 36,
+  },
+  "transform-es2015-parameters": {
+    edge: 14,
+    firefox: Number.NEGATIVE_INFINITY,
+    chrome: 49,
+    opera: 36,
+  },
+  "transform-es2015-shorthand-properties": {
+    edge: 12,
+    firefox: 33,
+    chrome: 43,
+    opera: 30
+  },
+  "transform-es2015-spread": {
+    edge: 13,
+    firefox: 36,
+    chrome: 46,
+    opera: 33,
+  },
+  "transform-es2015-sticky-regex": {
+    edge: 13,
+    firefox: 31,
+    chrome: 49,
+    opera: 36
+  },
+  "transform-es2015-template-literals": {
+    edge: 13,
+    firefox: 34,
+    chrome: 41,
+    opera: 28,
+  },
+  "transform-es2015-typeof-symbol": {
+    edge: 12,
+    firefox: 36,
+    chrome: 38,
+    opera: 25,
+  },
+  "transform-es2015-unicode-regex": {
+    edge: 12,
+    firefox: 46,
+    chrome: 51,
+    opera: 38,
+  },
+  "transform-regenerator": {
+    edge: 13,
+    firefox: 45,
+    chrome: 49,
+    opera: 36,
+  },
+
+  // es2016
+  "transform-exponentiation-operator": {
+    edge: 14,
+    chrome: 52,
+  },
+
+  // es2017
+  "transform-async-to-generator": {
+    edge: 14,
+  },
+  "syntax-trailing-function-commas": {
+    edge: 14,
+  }
+};
diff --git a/experimental/babel-preset-env/test/index.js b/experimental/babel-preset-env/test/index.js
new file mode 100644
index 0000000000..b1720bdf01
--- /dev/null
+++ b/experimental/babel-preset-env/test/index.js
@@ -0,0 +1,32 @@
+"use strict";
+
+const babelPresetEnv = require("../lib/index.js");
+const assert = require("assert");
+
+describe("babel-preset-env", () => {
+  describe("isPluginRequired", () => {
+    it("returns true if no targets are specified", () => {
+      const isRequired = babelPresetEnv.isPluginRequired({}, {});
+      assert(isRequired);
+    });
+    it("returns true if plugin feature is not implemented in one or more targets", () => {
+      let targets;
+      const plugin = {
+        edge: false,
+        firefox: 45,
+        chrome: 49,
+      }
+
+      targets = {
+        "chrome": Number.MAX_SAFE_INTEGER,
+        "firefox": Number.MAX_SAFE_INTEGER
+      };
+      assert(babelPresetEnv.isPluginRequired(targets, plugin) === false);
+
+      targets = {
+        "edge": 12,
+      };
+      assert(babelPresetEnv.isPluginRequired(plugin, plugin) === true);
+    });
+  });
+});