title: Cannot use JSX unless the '--jsx' flag is provided when "jsx" is "react-jsx"
body: <p>typescript throws:</p>
  <blockquote>
  <p>Cannot use JSX unless the '--jsx' flag is provided.ts(17004)</p>
  </blockquote>
  <p>After changing <code>tsconfig.json</code> <code>jsx</code> to <code>react-jsx</code>, jsx works. <code>yarn start</code> changes tsconfig.json to <code>react-jsx</code> again.</p>
  <p><code>react-scripts</code> was updated to 4.0.1.</p>
  <p>package.json</p>
  <pre><code>&quot;dependencies&quot;: {
      &quot;react&quot;: &quot;^17.0.1&quot;,
      &quot;react-dom&quot;: &quot;^17.0.1&quot;,
      &quot;react-scripts&quot;: &quot;4.0.1&quot;,
      &quot;semantic-ui-css&quot;: &quot;^2.4.1&quot;,
    },
    &quot;devDependencies&quot;: {
      &quot;@testing-library/jest-dom&quot;: &quot;^5.11.4&quot;,
      &quot;@testing-library/react&quot;: &quot;^11.2.2&quot;,
      &quot;@testing-library/user-event&quot;: &quot;^12.1.10&quot;,
      &quot;@types/jest&quot;: &quot;^26.0.15&quot;,
      &quot;@types/node&quot;: &quot;^14.14.9&quot;,
      &quot;@types/react&quot;: &quot;^17.0.0&quot;,
      &quot;@types/react-dom&quot;: &quot;^17.0.0&quot;,
      &quot;@typescript-eslint/eslint-plugin&quot;: &quot;^4.8.1&quot;,
      &quot;@typescript-eslint/parser&quot;: &quot;^4.8.1&quot;,
      &quot;eslint-config-react&quot;: &quot;^1.1.7&quot;,
      &quot;eslint-plugin-react&quot;: &quot;^7.21.5&quot;,
      &quot;eslint-plugin-react-hooks&quot;: &quot;^4.2.0&quot;,
      &quot;typescript&quot;: &quot;^4.1.2&quot;
    },
  </code></pre>
  <p>tsconfig.json</p>
  <pre><code>{
    &quot;compilerOptions&quot;: {
      &quot;target&quot;: &quot;es5&quot;,
      &quot;lib&quot;: [
        &quot;dom&quot;,
        &quot;dom.iterable&quot;,
        &quot;esnext&quot;
      ],
      &quot;allowJs&quot;: true,
      &quot;skipLibCheck&quot;: true,
      &quot;esModuleInterop&quot;: true,
      &quot;allowSyntheticDefaultImports&quot;: true,
      &quot;strict&quot;: true,
      &quot;forceConsistentCasingInFileNames&quot;: true,
      &quot;noFallthroughCasesInSwitch&quot;: true,
      &quot;module&quot;: &quot;esnext&quot;,
      &quot;moduleResolution&quot;: &quot;node&quot;,
      &quot;resolveJsonModule&quot;: true,
      &quot;isolatedModules&quot;: true,
      &quot;noEmit&quot;: true,
      &quot;jsx&quot;: &quot;react-jsx&quot;
    },
    &quot;include&quot;: [
      &quot;src&quot;
    ]
  }
  </code></pre>
  <p>How to fix this?</p>