[system] Don't spread props to DOM for string tags

packages/mui-system/src/createStyled.js

@@ -8,6 +8,17 @@ function isEmpty(obj) {
   return Object.keys(obj).length === 0;
 }
 
+// https://github.com/emotion-js/emotion/blob/26ded6109fcd8ca9875cc2ce4564fee678a3f3c5/packages/styled/src/utils.js#L40
+function isStringTag(tag) {
+  return (
+    typeof tag === 'string' &&
+    // 96 is one less than the char code
+    // for "a" so this is checking that
+    // it's a lowercase character
+    tag.charCodeAt(0) > 96
+  );
+}
+
 const getStyleOverrides = (name, theme) => {
   if (theme.components && theme.components[name] && theme.components[name].styleOverrides) {
     return theme.components[name].styleOverrides;
@@ -104,6 +115,9 @@ export default function createStyled(input = {}) {
     } else if (componentSlot) {
       // any other slot specified
       shouldForwardPropOption = slotShouldForwardProp;
+    } else if (isStringTag(tag)) {
+      // for string (html) tag, preserve the behavior in emotion & styled-components.
+      shouldForwardPropOption = undefined;
     }
 
     const defaultStyledResolver = styledEngineStyled(tag, {

packages/mui-system/src/createStyled.test.js

@@ -281,4 +281,57 @@ describe('createStyled', () => {
       });
     });
   });
+
+  it('does not spread `sx` prop to DOM', () => {
+    const styled = createStyled({});
+    const Button = styled('button')({});
+
+    const { container } = render(<Button sx={{ bgcolor: 'red' }}>Link</Button>);
+    expect(container.firstChild).not.to.have.attribute('sx');
+  });
+
+  it('does not forward `ownerState` prop to DOM', () => {
+    const styled = createStyled({});
+    const Button = styled('button')({});
+
+    const { container } = render(<Button ownerState={{}} />);
+    expect(container.firstChild).not.to.have.attribute('ownerState');
+  });
+
+  describe('default behaviors', () => {
+    it('does not forward invalid props to DOM if no `slot` specified', () => {
+      // This scenario is usually used by library consumers
+      const styled = createStyled({});
+      const Button = styled('button')({});
+
+      const { container } = render(
+        <Button color="red" shouldBeRemoved data-foo="bar">
+          Link
+        </Button>,
+      );
+      expect(container.firstChild.getAttribute('data-foo')).to.equal('bar');
+      expect(container.firstChild.getAttribute('color')).to.equal('red'); // color is for Safari mask-icon link
+      expect(container.firstChild.getAttribute('shouldBeRemoved')).not.to.equal('true');
+    });
+
+    it('can use `as` prop', () => {
+      const styled = createStyled({});
+      const Button = styled('button')({});
+
+      const { container } = render(<Button as="a" href="/" />);
+
+      expect(container.firstChild).to.have.tagName('a');
+      expect(container.firstChild).to.have.attribute('href', '/');
+    });
+
+    it('able to pass props to `as` styled component', () => {
+      const styled = createStyled({});
+      const ChildRoot = styled('div')({});
+      const Child = ({ component }) => <ChildRoot as={component}>content</ChildRoot>;
+      const Button = styled('button')({});
+      const { container } = render(<Button as={Child} component="span" />);
+
+      expect(container.firstChild).to.have.tagName('span');
+    });
+  });
 });