[docs-infra] Preserve normal body font weight

packages-internal/core-docs/src/nextFonts/index.ts

@@ -61,4 +61,9 @@ export const fonts = [
   roboto,
 ];
 
-export const fontClasses = fonts.map((font) => font.className).join(' ');
+// The single-weight General Sans class sets font-weight: 600 on body. The import
+// still registers and preloads the font, so the class is not necessary.
+export const fontClasses = fonts
+  .filter((font) => font !== generalSans)
+  .map((font) => font.className)
+  .join(' ');

test/e2e-website/docs-fonts.spec.ts

@@ -0,0 +1,55 @@
+import { test as base, expect } from '@playwright/test';
+import { TestFixture } from './playwright.config';
+
+const test = base.extend<TestFixture>({});
+
+for (const javaScriptEnabled of [false, true]) {
+  test.describe(`Docs fonts (${javaScriptEnabled ? 'hydrated' : 'server-rendered'})`, () => {
+    test.use({ javaScriptEnabled });
+
+    test('keeps normal body text and semibold headings', async ({ page }) => {
+      await page.goto('/material-ui/getting-started/installation/');
+      if (javaScriptEnabled) {
+        await expect(page.locator('body')).toHaveAttribute('dir', 'ltr');
+      }
+
+      await expect(page.locator('body')).toHaveCSS('font-weight', '400');
+
+      // Use plain elements to check inheritance without component typography styles.
+      const inheritedWeights = await page.evaluate(() => {
+        const container = document.createElement('div');
+        container.innerHTML =
+          '<p>Paragraph</p><label>Label</label><fieldset><legend>Legend</legend></fieldset>';
+        document.body.appendChild(container);
+        const weights = Array.from(
+          container.querySelectorAll('p, label, legend'),
+          (element) => getComputedStyle(element).fontWeight,
+        );
+        container.remove();
+        return weights;
+      });
+      expect(inheritedWeights).toEqual(['400', '400', '400']);
+
+      const heading = page.getByRole('heading', { name: 'Installation', exact: true });
+      await expect(heading).toHaveCSS('font-weight', '600');
+      await expect(heading).toHaveCSS('font-family', /General Sans/);
+
+      // The declared font-family does not prove that the font face loads.
+      // The dev server injects font CSS with JavaScript, so check only when hydrated.
+      if (javaScriptEnabled) {
+        await expect
+          .poll(() =>
+            page.evaluate(() =>
+              Array.from(document.fonts).some(
+                (font) =>
+                  font.family.replace(/"/g, '') === 'General Sans' &&
+                  font.weight === '600' &&
+                  font.status === 'loaded',
+              ),
+            ),
+          )
+          .toBe(true);
+      }
+    });
+  });
+}