fixes #9382: inline forms now require use of .form-group for proper alignment of all form controls

less/forms.less

@@ -293,28 +293,44 @@ textarea {
 
 // Inline forms
 //
-// Make forms appear inline(-block).
+// Make forms appear inline(-block) by adding the `.form-inline` class. Inline
+// forms begin stacked on extra small (mobile) devices and then go inline when
+// viewports reach <768px.
+//
+// Requires wrapping inputs and labels with `.form-group` for proper display of
+// default HTML form controls and our custom form controls (e.g., input groups).
 
 .form-inline {
-  .form-control,
-  .radio,
-  .checkbox {
-    display: inline-block;
-  }
 
-  // Remove default margin on radios/checkboxes that were used for stacking, and
-  // then undo the floating of radios and checkboxes to match (which also avoids
-  // a bug in WebKit: https://github.com/twbs/bootstrap/issues/1969).
-  .radio,
-  .checkbox {
-    margin-top: 0;
-    margin-bottom: 0;
-    padding-left: 0;
-  }
-  .radio input[type="radio"],
-  .checkbox input[type="checkbox"] {
-    float: none;
-    margin-left: 0;
+  // Kick in the inline
+  @media (min-width: @screen-tablet) {
+    // Inline-block all the things for "inline"
+    .form-group  {
+      display: inline-block;
+      margin-bottom: 0;
+      vertical-align: middle;
+    }
+
+    // Reset form control's default 100% width
+    .form-control {
+      width: auto;
+    }
+
+    // Remove default margin on radios/checkboxes that were used for stacking, and
+    // then undo the floating of radios and checkboxes to match (which also avoids
+    // a bug in WebKit: https://github.com/twbs/bootstrap/issues/1969).
+    .radio,
+    .checkbox {
+      display: inline-block;
+      margin-top: 0;
+      margin-bottom: 0;
+      padding-left: 0;
+    }
+    .radio input[type="radio"],
+    .checkbox input[type="checkbox"] {
+      float: none;
+      margin-left: 0;
+    }
   }
 }