From ba0e466c4ef7b5c19ea2c5ae4affc265d070cc42 Mon Sep 17 00:00:00 2001
From: Ian Sutherland <ian@iansutherland.ca>
Date: Thu, 22 Oct 2020 21:10:23 -0600
Subject: [PATCH] Also check react version before setting jsx value in tsconfig

---
 .../scripts/utils/verifyTypeScriptSetup.js    | 20 +++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/packages/react-scripts/scripts/utils/verifyTypeScriptSetup.js b/packages/react-scripts/scripts/utils/verifyTypeScriptSetup.js
index b6f7edead4c..9942013ad32 100644
--- a/packages/react-scripts/scripts/utils/verifyTypeScriptSetup.js
+++ b/packages/react-scripts/scripts/utils/verifyTypeScriptSetup.js
@@ -18,6 +18,19 @@ const semver = require('semver');
 const immer = require('react-dev-utils/immer').produce;
 const globby = require('react-dev-utils/globby').sync;
 
+const hasJsxRuntime = (() => {
+  if (process.env.DISABLE_NEW_JSX_TRANSFORM === 'true') {
+    return false;
+  }
+
+  try {
+    require.resolve('react/jsx-runtime', { paths: [paths.appPath] });
+    return true;
+  } catch (e) {
+    return false;
+  }
+})();
+
 function writeJson(fileName, object) {
   fs.writeFileSync(
     fileName,
@@ -134,8 +147,11 @@ function verifyTypeScriptSetup() {
     noEmit: { value: true },
     jsx: {
       parsedValue: ts.JsxEmit.React,
-      value: semver.gte(ts.version, '4.1.0-beta') ? 'react-jsx' : 'react',
-      reason: 'to support the new JSX transform in React 17'
+      value:
+        hasJsxRuntime && semver.gte(ts.version, '4.1.0-beta')
+          ? 'react-jsx'
+          : 'react',
+      reason: 'to support the new JSX transform in React 17',
     },
     paths: { value: undefined, reason: 'aliased imports are not supported' },
   };