Form check markup v2 (#25050)

* match layout behaviors

* ditch the indicator as separate element for psuedo-elements on the label

* move disabled to attribute only on input

* redo default inline check to support new markup

* redo inline forms

* clean up vars

* update validation mixin to new structure

* update checks in docs

* linting for for/id attributes

scss/_custom-forms.scss

@@ -9,9 +9,13 @@
 
 .custom-control {
   position: relative;
-  display: inline-flex;
+  display: block;
   min-height: (1rem * $line-height-base);
   padding-left: $custom-control-gutter;
+}
+
+.custom-control-inline {
+  display: inline-flex;
   margin-right: $custom-control-spacer-x;
 }
 
@@ -20,51 +24,61 @@
   z-index: -1; // Put the input behind the label so it doesn't overlay text
   opacity: 0;
 
-  &:checked ~ .custom-control-indicator {
+  &:checked ~ .custom-control-label::before {
     color: $custom-control-indicator-checked-color;
     @include gradient-bg($custom-control-indicator-checked-bg);
     @include box-shadow($custom-control-indicator-checked-box-shadow);
   }
 
-  &:focus ~ .custom-control-indicator {
+  &:focus ~ .custom-control-label::before {
     // the mixin is not used here to make sure there is feedback
     box-shadow: $custom-control-indicator-focus-box-shadow;
   }
 
-  &:active ~ .custom-control-indicator {
+  &:active ~ .custom-control-label::before {
     color: $custom-control-indicator-active-color;
     background-color: $custom-control-indicator-active-bg;
     @include box-shadow($custom-control-indicator-active-box-shadow);
   }
 
   &:disabled {
-    ~ .custom-control-indicator {
-      background-color: $custom-control-indicator-disabled-bg;
-    }
+    ~ .custom-control-label {
+      color: $custom-control-label-disabled-color;
 
-    ~ .custom-control-description {
-      color: $custom-control-description-disabled-color;
+      &::before {
+        background-color: $custom-control-indicator-disabled-bg;
+      }
     }
   }
 }
 
-// Custom indicator
+// Custom control indicators
 //
-// Generates a shadow element to create our makeshift checkbox/radio background.
+// Build the custom controls out of psuedo-elements.
 
-.custom-control-indicator {
-  position: absolute;
-  top: (($line-height-base - $custom-control-indicator-size) / 2);
-  left: 0;
-  display: block;
-  width: $custom-control-indicator-size;
-  height: $custom-control-indicator-size;
-  pointer-events: none;
-  user-select: none;
-  background-color: $custom-control-indicator-bg;
-  @include box-shadow($custom-control-indicator-box-shadow);
+.custom-control-label {
+  margin-bottom: 0;
 
+  // Background-color and (when enabled) gradient
   &::before {
+    position: absolute;
+    top: (($line-height-base - $custom-control-indicator-size) / 2);
+    left: 0;
+    display: block;
+    width: $custom-control-indicator-size;
+    height: $custom-control-indicator-size;
+    pointer-events: none;
+    content: "";
+    user-select: none;
+    background-color: $custom-control-indicator-bg;
+    @include box-shadow($custom-control-indicator-box-shadow);
+  }
+
+  // Foreground (icon)
+  &::after {
+    position: absolute;
+    top: (($line-height-base - $custom-control-indicator-size) / 2);
+    left: 0;
     display: block;
     width: $custom-control-indicator-size;
     height: $custom-control-indicator-size;
@@ -75,28 +89,31 @@
   }
 }
 
+
 // Checkboxes
 //
 // Tweak just a few things for checkboxes.
 
 .custom-checkbox {
-  .custom-control-indicator {
+  .custom-control-label::before {
     @include border-radius($custom-checkbox-indicator-border-radius);
   }
 
-  .custom-control-input:checked ~ .custom-control-indicator {
-    @include gradient-bg($custom-control-indicator-checked-bg);
-
+  .custom-control-input:checked ~ .custom-control-label {
     &::before {
+      @include gradient-bg($custom-control-indicator-checked-bg);
+    }
+    &::after {
       background-image: $custom-checkbox-indicator-icon-checked;
     }
   }
 
-  .custom-control-input:indeterminate ~ .custom-control-indicator {
-    @include gradient-bg($custom-checkbox-indicator-indeterminate-bg);
-    @include box-shadow($custom-checkbox-indicator-indeterminate-box-shadow);
-
+  .custom-control-input:indeterminate ~ .custom-control-label {
     &::before {
+      @include gradient-bg($custom-checkbox-indicator-indeterminate-bg);
+      @include box-shadow($custom-checkbox-indicator-indeterminate-box-shadow);
+    }
+    &::after {
       background-image: $custom-checkbox-indicator-icon-indeterminate;
     }
   }
@@ -107,34 +124,16 @@
 // Tweak just a few things for radios.
 
 .custom-radio {
-  .custom-control-indicator {
+  .custom-control-label::before {
     border-radius: $custom-radio-indicator-border-radius;
   }
 
-  .custom-control-input:checked ~ .custom-control-indicator {
-    @include gradient-bg($custom-control-indicator-checked-bg);
-
+  .custom-control-input:checked ~ .custom-control-label {
     &::before {
-      background-image: $custom-radio-indicator-icon-checked;
+      @include gradient-bg($custom-control-indicator-checked-bg);
     }
-  }
-}
-
-
-// Layout options
-//
-// By default radios and checkboxes are `inline-block` with no additional spacing
-// set. Use these optional classes to tweak the layout.
-
-.custom-controls-stacked {
-  display: flex;
-  flex-direction: column;
-
-  .custom-control {
-    margin-bottom: $custom-control-spacer-y;
-
-    + .custom-control {
-      margin-left: 0;
+    &::after {
+      background-image: $custom-radio-indicator-icon-checked;
     }
   }
 }