From 665915214510873351b5136e4afffff76e021024 Mon Sep 17 00:00:00 2001
From: Jack Turnbull <git@jack.codes>
Date: Wed, 18 Dec 2019 20:53:59 +0000
Subject: [PATCH] build: relax transpilation for es modules (#3337)

* build: relax transpilation for es modules

ES module output currently includes regenerator runtime functions which
can block strict content security policies. For an ES module output this
isn't required because any runtime supporting ES modules will also
support async/await natively. It is also highly likely that users of the
ES module would also be performing their own transipliation of
async/await and we should not make assumptions on their behalf (some may
prefer promises to regenerator, for example).

This commit splits the babel config into two; an unchanged one for the
UMD output, and another for module output.

* build: override babel settings from plugin
---
 config/babel/babel.config.cjs  | 11 -----------
 config/rollup/rollup.config.js | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 31 insertions(+), 12 deletions(-)
 delete mode 100644 config/babel/babel.config.cjs

diff --git a/config/babel/babel.config.cjs b/config/babel/babel.config.cjs
deleted file mode 100644
index f2c264e1d..000000000
--- a/config/babel/babel.config.cjs
+++ /dev/null
@@ -1,11 +0,0 @@
-module.exports = {
-  presets: [
-    '@babel/preset-typescript',
-    ['@babel/preset-env', { modules: false }],
-    '@babel/preset-react',
-  ],
-  plugins: [
-    '@babel/plugin-transform-runtime',
-    '@babel/plugin-proposal-class-properties',
-  ],
-}
diff --git a/config/rollup/rollup.config.js b/config/rollup/rollup.config.js
index 4c5734ac6..84e4ec532 100644
--- a/config/rollup/rollup.config.js
+++ b/config/rollup/rollup.config.js
@@ -90,7 +90,37 @@ function configure(pkg, env, target) {
       runtimeHelpers: true,
       include: [`packages/${pkg.name}/src/**`],
       extensions: ['.js', '.ts'],
-      configFile: './config/babel/babel.config.cjs',
+      presets: [
+        '@babel/preset-typescript',
+        [
+          '@babel/preset-env',
+          isUmd
+            ? { modules: false }
+            : {
+                exclude: [
+                  '@babel/plugin-transform-regenerator',
+                  '@babel/transform-async-to-generator',
+                ],
+                modules: false,
+                targets: {
+                  esmodules: true,
+                },
+              },
+        ],
+        '@babel/preset-react',
+      ],
+      plugins: [
+        [
+          '@babel/plugin-transform-runtime',
+          isUmd
+            ? {}
+            : {
+                regenerator: false,
+                useESModules: true,
+              },
+        ],
+        '@babel/plugin-proposal-class-properties',
+      ],
     }),
 
     // Register Node.js globals for browserify compatibility.