Throw upgrade error when babel version is less than 6.14.0 (#116)

* Throw upgrade error when babel version is less than 6.14.0

+ (Close #70)
+ related #114

* Update error message

* Simplify

packages/babel-preset-babili/src/index.js

@@ -1,20 +1,50 @@
+const err = new Error("Babili requires babel-core>=6.14.0. Upgrade babel-core or tools dependent on babel-core to recent versions");
+
+function isVersion(versionStr) {
+  const version = versionStr.split(".").map((p) => parseInt(p));
+  return version[0] >= 6 && version[1] >= 14;
+}
+
 module.exports = {
-  minified: true,
-  plugins: [
-    require("babel-plugin-minify-constant-folding"),
-    require("babel-plugin-minify-dead-code-elimination"),
-    require("babel-plugin-minify-flip-comparisons"),
-    require("babel-plugin-minify-guarded-expressions"),
-    require("babel-plugin-minify-infinity"),
-    require("babel-plugin-minify-mangle-names"),
-    require("babel-plugin-minify-replace"),
-    require("babel-plugin-minify-simplify"),
-    require("babel-plugin-minify-type-constructors"),
-    require("babel-plugin-transform-member-expression-literals"),
-    require("babel-plugin-transform-merge-sibling-variables"),
-    require("babel-plugin-transform-minify-booleans"),
-    require("babel-plugin-transform-property-literals"),
-    require("babel-plugin-transform-simplify-comparison-operators"),
-    require("babel-plugin-transform-undefined-to-void"),
-  ],
+  plugins: [function({version}) {
+    if (!isVersion(version)) {
+      throw err;
+    }
+    return {
+      visitor: {}
+    };
+  }],
 };
+
+Object.defineProperty(module.exports, "buildPreset", {
+  configurable: true,
+  writable: true,
+  enumerable: false,
+  value: preset
+});
+
+function preset(context) {
+  if (!isVersion(context.version)) {
+    throw err;
+  }
+  return {
+    minified: true,
+    plugins: [
+      require("babel-plugin-minify-constant-folding"),
+      require("babel-plugin-minify-dead-code-elimination"),
+      require("babel-plugin-minify-flip-comparisons"),
+      require("babel-plugin-minify-guarded-expressions"),
+      require("babel-plugin-minify-infinity"),
+      require("babel-plugin-minify-mangle-names"),
+      require("babel-plugin-minify-replace"),
+      require("babel-plugin-minify-simplify"),
+      require("babel-plugin-minify-type-constructors"),
+      require("babel-plugin-transform-member-expression-literals"),
+      require("babel-plugin-transform-merge-sibling-variables"),
+      require("babel-plugin-transform-minify-booleans"),
+      require("babel-plugin-transform-property-literals"),
+      require("babel-plugin-transform-simplify-comparison-operators"),
+      require("babel-plugin-transform-undefined-to-void"),
+    ],
+  };
+}