[system] Add experimental_sx utility

docs/src/pages/system/styled/UsingWithSx.js

@@ -0,0 +1,33 @@
+import * as React from 'react';
+import {
+  styled,
+  createTheme,
+  ThemeProvider,
+  experimental_sx as sx,
+} from '@mui/system';
+
+const customTheme = createTheme({
+  palette: {
+    primary: {
+      main: '#1976d2',
+      contrastText: 'white',
+    },
+  },
+});
+
+const MyThemeComponent = styled('div')(
+  sx({
+    color: 'primary.contrastText',
+    backgroundColor: 'primary.main',
+    padding: 1,
+    borderRadius: 1,
+  }),
+);
+
+export default function ThemeUsage() {
+  return (
+    <ThemeProvider theme={customTheme}>
+      <MyThemeComponent>Styled div with theme</MyThemeComponent>
+    </ThemeProvider>
+  );
+}

docs/src/pages/system/styled/UsingWithSx.tsx

@@ -0,0 +1,33 @@
+import * as React from 'react';
+import {
+  styled,
+  createTheme,
+  ThemeProvider,
+  experimental_sx as sx,
+} from '@mui/system';
+
+const customTheme = createTheme({
+  palette: {
+    primary: {
+      main: '#1976d2',
+      contrastText: 'white',
+    },
+  },
+});
+
+const MyThemeComponent = styled('div')(
+  sx({
+    color: 'primary.contrastText',
+    backgroundColor: 'primary.main',
+    padding: 1,
+    borderRadius: 1,
+  }),
+);
+
+export default function ThemeUsage() {
+  return (
+    <ThemeProvider theme={customTheme}>
+      <MyThemeComponent>Styled div with theme</MyThemeComponent>
+    </ThemeProvider>
+  );
+}

docs/src/pages/system/styled/UsingWithSx.tsx.preview

@@ -0,0 +1,3 @@
+<ThemeProvider theme={customTheme}>
+  <MyThemeComponent>Styled div with theme</MyThemeComponent>
+</ThemeProvider>

docs/src/pages/system/styled/styled.md

@@ -196,6 +196,16 @@ const MyStyledButton = (props) => (
 })
 ```
 
+### How can I use the `sx` syntax with the `styled()` utility?
+
+If you are one of those that prefer the `sx` syntax and want to use it in both the `sx` prop and the `styled()` utility, you can do this by using the `experimental_sx` utility from the `@mui/system`:
+
+{{"demo": "pages/system/styled/UsingWithSx.js", "defaultCodeOpen": true}}
+
+The overhead added by using the `experimental_sx` utility is the same as if you were to use the `sx` prop on the component.
+
+> Note: You can use the `experimental_sx` outside of the `styled()` utility too, for example for defining the `variants` in your custom theme.
+
 ## How to use components selector API
 
 If you've ever used the `styled()` API of either [`emotion`](https://emotion.sh/docs/styled#targeting-another-emotion-component) or [`styled-components`](https://styled-components.com/docs/advanced#referring-to-other-components), you should have been able to use components as selectors.

packages/mui-material/src/styles/index.d.ts

@@ -55,6 +55,7 @@ export {
   lighten,
   ColorFormat,
   ColorObject,
+  experimental_sx,
 } from '@mui/system';
 export { default as useTheme } from './useTheme';
 export { default as useThemeProps } from './useThemeProps';

packages/mui-material/src/styles/index.js

@@ -13,6 +13,7 @@ export {
   lighten,
   css,
   keyframes,
+  experimental_sx,
 } from '@mui/system';
 export { default as createTheme, createMuiTheme } from './createTheme';
 export { default as unstable_createMuiStrictModeTheme } from './createMuiStrictModeTheme';

packages/mui-material/src/styles/index.spec.ts

@@ -0,0 +1,27 @@
+import { experimental_sx as sx, styled, createTheme } from '@mui/material/styles';
+
+// Can use the experimental_sx in the styled() utility
+const Test = styled('div')(
+  sx({
+    color: 'primary.main',
+    bgcolor: 'primary.light',
+    m: 2,
+  }),
+);
+
+// Can use the experimental_sx in the theme's variants
+const customTheme = createTheme({
+  components: {
+    MuiButton: {
+      variants: [
+        {
+          props: {},
+          style: sx({
+            m: 2,
+            p: 1,
+          }),
+        },
+      ],
+    },
+  },
+});

packages/mui-system/src/index.d.ts

@@ -121,6 +121,8 @@ export {
 } from './styleFunctionSx';
 export * from './styleFunctionSx';
 
+export { default as experimental_sx } from './sx';
+
 export { default as Box } from './Box';
 export * from './Box';
 

packages/mui-system/src/index.js

@@ -29,6 +29,7 @@ export {
   default as unstable_styleFunctionSx,
   extendSxProp as unstable_extendSxProp,
 } from './styleFunctionSx';
+export { default as experimental_sx } from './sx';
 export { default as unstable_getThemeValue } from './getThemeValue';
 export { default as Box } from './Box';
 export { default as createBox } from './createBox';

packages/mui-system/src/sx/index.d.ts

@@ -0,0 +1 @@
+export { default } from './sx';

packages/mui-system/src/sx/index.js

@@ -0,0 +1 @@
+export { default } from './sx';

packages/mui-system/src/sx/sx.d.ts

@@ -0,0 +1,4 @@
+import { CSSObject } from '@mui/styled-engine';
+import { SxProps } from '../styleFunctionSx';
+
+export default function sx<T extends object = {}>(styles: SxProps<T>): CSSObject;

packages/mui-system/src/sx/sx.js

@@ -0,0 +1,7 @@
+import styleFunctionSx from '../styleFunctionSx';
+
+function sx(styles) {
+  return ({ theme }) => styleFunctionSx({ sx: styles, theme });
+}
+
+export default sx;

packages/mui-system/src/sx/sx.spec.ts

@@ -0,0 +1,10 @@
+import { experimental_sx as sx, styled } from '@mui/system';
+
+// Can be used in the styled() utility
+const Test = styled('div')(
+  sx({
+    color: 'primary.main',
+    bgcolor: 'primary.light',
+    m: 2,
+  }),
+);

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

@@ -0,0 +1,143 @@
+import * as React from 'react';
+import { expect } from 'chai';
+import { createRenderer } from 'test/utils';
+import { experimental_sx as sx, styled, ThemeProvider } from '@mui/system';
+
+describe('sx', () => {
+  const { render } = createRenderer();
+  const breakpointsValues = {
+    xs: 0,
+    sm: 600,
+    md: 960,
+    lg: 1280,
+    xl: 1920,
+  };
+
+  const round = (value) => Math.round(value * 1e5) / 1e5;
+
+  const theme = {
+    spacing: (val) => `${val * 10}px`,
+    breakpoints: {
+      keys: ['xs', 'sm', 'md', 'lg', 'xl'],
+      values: breakpointsValues,
+      up: (key) => {
+        return `@media (min-width:${breakpointsValues[key]}px)`;
+      },
+    },
+    unit: 'px',
+    palette: {
+      primary: {
+        main: 'rgb(0, 0, 255)',
+      },
+      secondary: {
+        main: 'rgb(0, 255, 0)',
+      },
+    },
+    typography: {
+      fontFamily: '"Roboto", "Helvetica", "Arial", sans-serif',
+      fontWeightLight: 300,
+      fontSize: 14,
+      body1: {
+        fontFamily: '"Roboto", "Helvetica", "Arial", sans-serif',
+        fontSize: '1rem',
+        letterSpacing: `${round(0.15 / 16)}em`,
+        fontWeight: 400,
+        lineHeight: 1.5,
+      },
+      body2: {
+        fontFamily: '"Roboto", "Helvetica", "Arial", sans-serif',
+        fontSize: `${14 / 16}rem`,
+        letterSpacing: `${round(0.15 / 14)}em`,
+        fontWeight: 400,
+        lineHeight: 1.43,
+      },
+    },
+  };
+
+  describe('system', () => {
+    it('resolves system when used inside styled()', function test() {
+      if (/jsdom/.test(window.navigator.userAgent)) {
+        this.skip();
+      }
+
+      const Test = styled('div')(
+        sx({
+          color: 'primary.main',
+          bgcolor: 'secondary.main',
+          m: 2,
+          p: 1,
+          fontSize: 'fontSize',
+          maxWidth: 'sm',
+        }),
+      );
+
+      const { container } = render(
+        <ThemeProvider theme={theme}>
+          <Test />
+        </ThemeProvider>,
+      );
+
+      expect(container.firstChild).toHaveComputedStyle({
+        color: 'rgb(0, 0, 255)',
+        backgroundColor: 'rgb(0, 255, 0)',
+        margin: '20px',
+        padding: '10px',
+        fontSize: '14px',
+        maxWidth: '600px',
+      });
+    });
+
+    it('resolves system when used inside variants', function test() {
+      if (/jsdom/.test(window.navigator.userAgent)) {
+        this.skip();
+      }
+
+      const themeWithVariants = {
+        ...theme,
+        components: {
+          MuiTest: {
+            variants: [
+              {
+                props: {}, // all props
+                style: sx({
+                  color: 'primary.main',
+                  bgcolor: 'secondary.main',
+                  m: 2,
+                  p: 1,
+                  fontSize: 'fontSize',
+                  maxWidth: 'sm',
+                }),
+              },
+            ],
+          },
+        },
+      };
+
+      const Test = styled('div', { name: 'MuiTest', slot: 'Root' })(
+        sx({
+          color: 'primary.main',
+          bgcolor: 'secondary.main',
+          m: 2,
+          p: 1,
+          fontSize: 'fontSize',
+          maxWidth: 'sm',
+        }),
+      );
+
+      const { container } = render(
+        <ThemeProvider theme={themeWithVariants}>
+          <Test />
+        </ThemeProvider>,
+      );
+
+      expect(container.firstChild).toHaveComputedStyle({
+        color: 'rgb(0, 0, 255)',
+        backgroundColor: 'rgb(0, 255, 0)',
+        margin: '20px',
+        padding: '10px',
+        fontSize: '14px',
+        maxWidth: '600px',
+      });
+    });
+  });
+});