Update bootstrap

_sass/bootstrap/mixins/_forms.scss

@@ -10,7 +10,7 @@
 //
 // Example usage: change the default blue border and shadow to white for better
 // contrast against a dark gray background.
-@mixin form-control-focus() {
+@mixin form-control-focus($ignore-warning: false) {
   &:focus {
     color: $input-focus-color;
     background-color: $input-focus-bg;
@@ -23,8 +23,23 @@
       box-shadow: $input-focus-box-shadow;
     }
   }
+  @include deprecate("The `form-control-focus()` mixin", "v4.4.0", "v5", $ignore-warning);
 }
 
+// This mixin uses an `if()` technique to be compatible with Dart Sass
+// See https://github.com/sass/sass/issues/1873#issuecomment-152293725 for more details
+@mixin form-validation-state-selector($state) {
+  @if ($state == "valid" or $state == "invalid") {
+    .was-validated #{if(&, "&", "")}:#{$state},
+    #{if(&, "&", "")}.is-#{$state} {
+      @content;
+    }
+  } @else {
+    #{if(&, "&", "")}.is-#{$state} {
+      @content;
+    }
+  }
+}
 
 @mixin form-validation-state($state, $color, $icon) {
   .#{$state}-feedback {
@@ -50,16 +65,22 @@
     @include border-radius($form-feedback-tooltip-border-radius);
   }
 
+  @include form-validation-state-selector($state) {
+    ~ .#{$state}-feedback,
+    ~ .#{$state}-tooltip {
+      display: block;
+    }
+  }
+
   .form-control {
-    .was-validated &:#{$state},
-    &.is-#{$state} {
+    @include form-validation-state-selector($state) {
       border-color: $color;
 
       @if $enable-validation-icons {
         padding-right: $input-height-inner;
-        background-image: $icon;
+        background-image: escape-svg($icon);
         background-repeat: no-repeat;
-        background-position: center right $input-height-inner-quarter;
+        background-position: right $input-height-inner-quarter center;
         background-size: $input-height-inner-half $input-height-inner-half;
       }
 
@@ -67,18 +88,12 @@
         border-color: $color;
         box-shadow: 0 0 0 $input-focus-width rgba($color, .25);
       }
-
-      ~ .#{$state}-feedback,
-      ~ .#{$state}-tooltip {
-        display: block;
-      }
     }
   }
 
   // stylelint-disable-next-line selector-no-qualifying-type
   textarea.form-control {
-    .was-validated &:#{$state},
-    &.is-#{$state} {
+    @include form-validation-state-selector($state) {
       @if $enable-validation-icons {
         padding-right: $input-height-inner;
         background-position: top $input-height-inner-quarter right $input-height-inner-quarter;
@@ -87,41 +102,23 @@
   }
 
   .custom-select {
-    .was-validated &:#{$state},
-    &.is-#{$state} {
+    @include form-validation-state-selector($state) {
       border-color: $color;
 
       @if $enable-validation-icons {
         padding-right: $custom-select-feedback-icon-padding-right;
-        background: $custom-select-background, $icon $custom-select-bg no-repeat $custom-select-feedback-icon-position / $custom-select-feedback-icon-size;
+        background: $custom-select-background, escape-svg($icon) $custom-select-bg no-repeat $custom-select-feedback-icon-position / $custom-select-feedback-icon-size;
       }
 
       &:focus {
         border-color: $color;
         box-shadow: 0 0 0 $input-focus-width rgba($color, .25);
       }
-
-      ~ .#{$state}-feedback,
-      ~ .#{$state}-tooltip {
-        display: block;
-      }
-    }
-  }
-
-
-  .form-control-file {
-    .was-validated &:#{$state},
-    &.is-#{$state} {
-      ~ .#{$state}-feedback,
-      ~ .#{$state}-tooltip {
-        display: block;
-      }
     }
   }
 
   .form-check-input {
-    .was-validated &:#{$state},
-    &.is-#{$state} {
+    @include form-validation-state-selector($state) {
       ~ .form-check-label {
         color: $color;
       }
@@ -134,8 +131,7 @@
   }
 
   .custom-control-input {
-    .was-validated &:#{$state},
-    &.is-#{$state} {
+    @include form-validation-state-selector($state) {
       ~ .custom-control-label {
         color: $color;
 
@@ -144,11 +140,6 @@
         }
       }
 
-      ~ .#{$state}-feedback,
-      ~ .#{$state}-tooltip {
-        display: block;
-      }
-
       &:checked {
         ~ .custom-control-label::before {
           border-color: lighten($color, 10%);
@@ -170,17 +161,11 @@
 
   // custom file
   .custom-file-input {
-    .was-validated &:#{$state},
-    &.is-#{$state} {
+    @include form-validation-state-selector($state) {
       ~ .custom-file-label {
         border-color: $color;
       }
 
-      ~ .#{$state}-feedback,
-      ~ .#{$state}-tooltip {
-        display: block;
-      }
-
       &:focus {
         ~ .custom-file-label {
           border-color: $color;