From 5af16fdd48881f341b0fa42e8d0680022f2a120f Mon Sep 17 00:00:00 2001
From: Brijesh Bittu <brijeshb42@gmail.com>
Date: Mon, 27 May 2024 18:57:39 +0530
Subject: [PATCH] [material-ui][responsiveFontSizes] Handled undefined variants
 (#42412)

---
 .../mui-material/src/styles/responsiveFontSizes.js  |  5 +++++
 .../src/styles/responsiveFontSizes.test.js          | 13 +++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/packages/mui-material/src/styles/responsiveFontSizes.js b/packages/mui-material/src/styles/responsiveFontSizes.js
index fe0a5a6eda7d4f..e01b0a3e186c5c 100644
--- a/packages/mui-material/src/styles/responsiveFontSizes.js
+++ b/packages/mui-material/src/styles/responsiveFontSizes.js
@@ -34,6 +34,11 @@ export default function responsiveFontSizes(themeInput, options = {}) {
 
   variants.forEach((variant) => {
     const style = typography[variant];
+
+    if (!style) {
+      return;
+    }
+
     const remFontSize = parseFloat(convert(style.fontSize, 'rem'));
 
     if (remFontSize <= 1) {
diff --git a/packages/mui-material/src/styles/responsiveFontSizes.test.js b/packages/mui-material/src/styles/responsiveFontSizes.test.js
index 2383c2ecddd6c2..bf7da7e0d2a9ef 100644
--- a/packages/mui-material/src/styles/responsiveFontSizes.test.js
+++ b/packages/mui-material/src/styles/responsiveFontSizes.test.js
@@ -59,6 +59,19 @@ describe('responsiveFontSizes', () => {
     });
   });
 
+  it('should handle variants that have been reset to undefined', () => {
+    const theme = createTheme({
+      typography: {
+        h1: undefined,
+      },
+    });
+    const { typography } = responsiveFontSizes(theme, {
+      disableAlign: true,
+    });
+
+    expect(typography.h1).to.deep.equal(undefined);
+  });
+
   describe('when requesting a responsive typography with non unitless line height and alignment', () => {
     it('should throw an error, as this is not supported', () => {
       const theme = createTheme({