[core] Increase specificity to get correct style

Author: oliviertassinari

packages/material-ui/src/ButtonGroup/ButtonGroup.js

@@ -4,7 +4,11 @@ import clsx from 'clsx';
 import capitalize from '../utils/capitalize';
 import { fade } from '../styles/colorManipulator';
 import withStyles from '../styles/withStyles';
-import '../Button'; // So we don't have any override priority issue.
+import Button from '../Button';
+
+// Force a side effect so we don't have any override priority issue.
+// eslint-disable-next-line no-unused-expressions
+Button.styles;
 
 export const styles = theme => ({
   /* Styles applied to the root element. */

packages/material-ui/src/CardActions/CardActions.js

@@ -2,7 +2,6 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import clsx from 'clsx';
 import withStyles from '../styles/withStyles';
-import '../Button'; // So we don't have any override priority issue.
 
 export const styles = {
   /* Styles applied to the root element. */
@@ -13,7 +12,7 @@ export const styles = {
   },
   /* Styles applied to the root element if `disableSpacing={false}`. */
   spacing: {
-    '& > * + *': {
+    '& > :not(:first-child)': {
       marginLeft: 8,
     },
   },

packages/material-ui/src/DialogActions/DialogActions.js

@@ -2,7 +2,6 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import clsx from 'clsx';
 import withStyles from '../styles/withStyles';
-import '../Button'; // So we don't have any override priority issue.
 
 export const styles = {
   /* Styles applied to the root element. */
@@ -15,7 +14,7 @@ export const styles = {
   },
   /* Styles applied to the root element if `disableSpacing={false}`. */
   spacing: {
-    '& > * + *': {
+    '& > :not(:first-child)': {
       marginLeft: 8,
     },
   },

packages/material-ui/src/ExpansionPanelActions/ExpansionPanelActions.js

@@ -2,7 +2,6 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import clsx from 'clsx';
 import withStyles from '../styles/withStyles';
-import '../Button'; // So we don't have any override priority issue.
 
 export const styles = {
   /* Styles applied to the root element. */
@@ -14,7 +13,7 @@ export const styles = {
   },
   /* Styles applied to the root element if `disableSpacing={false}`. */
   spacing: {
-    '& > * + *': {
+    '& > :not(:first-child)': {
       marginLeft: 8,
     },
   },