Fix input group border radius issue (twbs#25075)

Author: ysds

scss/_input-group.scss

@@ -33,9 +33,8 @@
 
   .form-control,
   .custom-select {
-    &:not(:first-child):not(:last-of-type) { @include border-radius(0); }
-    &:first-child { @include border-right-radius(0); }
-    &:last-of-type:not(:first-child) { @include border-left-radius(0); }
+    &:not(:last-child) { @include border-right-radius(0); }
+    &:not(:first-child) { @include border-left-radius(0); }
   }
 
   // Custom file inputs have more complex markup, thus requiring different
@@ -44,12 +43,10 @@
     display: flex;
     align-items: center;
 
-    &:not(:first-child):not(:last-of-type) .custom-file-control,
-    &:not(:first-child):not(:last-of-type) .custom-file-control::before { @include border-radius(0); }
-    &:first-child .custom-file-control,
-    &:first-child .custom-file-control::before { @include border-right-radius(0); }
-    &:last-of-type:not(:first-child) .custom-file-control,
-    &:last-of-type:not(:first-child) .custom-file-control::before { @include border-left-radius(0); }
+    &:not(:last-child) .custom-file-control,
+    &:not(:last-child) .custom-file-control::before { @include border-right-radius(0); }
+    &:not(:first-child) .custom-file-control, 
+    &:not(:first-child) .custom-file-control::before { @include border-left-radius(0); }
   }
 }
 
@@ -139,28 +136,21 @@
 // border-radius values when extending. They're more specific than we'd like
 // with the `.input-group >` part, but without it, we cannot override the sizing.
 
+
 .input-group > .input-group-prepend > .btn,
-.input-group > .input-group-prepend > .input-group-text {
-  // All prepended buttons have no right border-radius
+.input-group > .input-group-prepend > .input-group-text,
+.input-group > .input-group-append:not(:last-child) > .btn,
+.input-group > .input-group-append:not(:last-child) > .input-group-text,
+.input-group > .input-group-append:last-child > .btn:not(:last-child):not(.dropdown-toggle),
+.input-group > .input-group-append:last-child > .input-group-text:not(:last-child), {
   @include border-right-radius(0);
-
-  + .btn,
-  + .input-group-text {
-    @include border-left-radius(0);
-  }
 }
 
-// We separate out the button and input resets here because `.input-group-text`
-// can be any HTML element, but buttons are always inputs, buttons, or anchors.
-.input-group > .input-group-append {
-  // Everything but the last one have no rounded corners
-  .btn:not(:last-of-type),
-  .input-group-text:not(:last-child) {
-    @include border-radius(0);
-  }
-
-  .btn:last-of-type,
-  .input-group-text:last-child {
-    @include border-left-radius(0);
-  }
+.input-group > .input-group-append > .btn,
+.input-group > .input-group-append > .input-group-text,
+.input-group > .input-group-prepend:not(:first-child) > .btn,
+.input-group > .input-group-prepend:not(:first-child) > .input-group-text,
+.input-group > .input-group-prepend:first-child > .btn:not(:first-child),
+.input-group > .input-group-prepend:first-child > .input-group-text:not(:first-child) {  
+  @include border-left-radius(0);
 }