Merge pull request #532 from cspotcode/import-babel-on-demand

Import babel deps on-demand, skipping if skipBabel is true

src/postprocess.ts

@@ -2,9 +2,20 @@
  * Postprocess step. Based on babel-jest: https://github.com/facebook/jest/blob/master/packages/babel-jest/src/index.js
  * https://github.com/facebook/jest/blob/9b157c3a7c325c3971b2aabbe4c8ab4ce0b0c56d/packages/babel-jest/src/index.js
  */
-import * as babel from 'babel-core';
-import istanbulPlugin from 'babel-plugin-istanbul';
-import * as jestPreset from 'babel-preset-jest';
+import * as __types__babel from 'babel-core';
+import __types__istanbulPlugin from 'babel-plugin-istanbul';
+import * as __types__jestPreset from 'babel-preset-jest';
+let babel: typeof __types__babel;
+let istanbulPlugin: typeof __types__istanbulPlugin;
+let jestPreset: typeof __types__jestPreset;
+function importBabelDeps() {
+    if (babel) {
+      return;
+    }
+    babel = require('babel-core');
+    istanbulPlugin = require('babel-plugin-istanbul').default;
+    jestPreset = require('babel-preset-jest');
+}
 import { CompilerOptions } from 'typescript/lib/typescript';
 import {
   BabelTransformOptions,
@@ -37,6 +48,7 @@ export function postProcessCode(
 function createBabelTransformer(
   options: BabelTransformOptions,
 ): PostProcessHook {
+  importBabelDeps();
   options = {
     ...options,
     plugins: options.plugins || [],