fix: segmented buttons

Author: kyledurand

polaris-react/src/components/Button/Button.scss

@@ -982,13 +982,15 @@
   }
 
   > :first-child .Button,
+  > :first-child .Button::before,
   > :first-child .Button::after {
     border-radius: 0;
     border-top-left-radius: var(--p-border-radius-2);
     border-bottom-left-radius: var(--p-border-radius-2);
   }
 
   > :last-child .Button,
+  > :last-child .Button::before,
   > :last-child .Button::after {
     border-radius: 0;
     border-top-right-radius: var(--p-border-radius-2);
@@ -1003,11 +1005,13 @@
 
 [data-buttongroup-connected-top='true'] {
   > :first-child .Button,
+  > :first-child .Button::before,
   > :first-child .Button::after {
     border-top-left-radius: 0;
   }
 
   > :last-child .Button,
+  > :last-child .Button::before,
   > :last-child .Button::after {
     border-top-right-radius: 0;
   }

polaris-react/src/components/Button/Button.stories.tsx

@@ -635,13 +635,16 @@ export function Split() {
   return (
     <div style={{height: '100px'}}>
       <ButtonGroup segmented>
-        <Button>Save</Button>
+        <Button variant="primary">Save</Button>
+
+        <div style={{width: '0px'}} />
 
         <Popover
           active={active}
           preferredAlignment="right"
           activator={
             <Button
+              variant="primary"
               onClick={() => setActive(true)}
               icon={ChevronDownMinor}
               accessibilityLabel="Other save actions"

polaris.shopify.com/pages/examples/button-split.tsx

@@ -8,13 +8,14 @@ function ButtonExample() {
   return (
     <div style={{height: '100px'}}>
       <ButtonGroup segmented>
-        <Button>Save</Button>
-
+        <Button variant="primary">Save</Button>
+        <div style={{width: '0px'}} />
         <Popover
           active={active}
           preferredAlignment="right"
           activator={
             <Button
+              variant="primary"
               onClick={() => setActive(true)}
               icon={ChevronDownMinor}
               accessibilityLabel="Other save actions"