Allow components to be imported without dependencies

CHANGELOG.md

@@ -2,6 +2,32 @@
 
 ## Unreleased
 
+### New features
+
+#### Improved Sass compilation times
+
+We've changed the way that dependencies are imported within GOV.UK Frontend to improve Sass compilation times.
+
+If you currently import `node_modules/govuk-frontend/govuk/all`, you will automatically benefit from these improvements.
+
+If you currently import a subset of GOV.UK Frontend:
+
+- you can now import `node-modules/govuk-frontend/govuk/base` instead of importing `node-modules/govuk-frontend/govuk/settings/all`, `node-modules/govuk-frontend/govuk/helpers/all` and `node-modules/govuk-frontend/govuk/tools/all`
+- you should import components using their `index` file, which will avoid importing the dependencies again
+
+For example:
+
+```scss
+@import "node_modules/govuk-frontend/govuk/base";
+
+@import "node_modules/govuk-frontend/govuk/core/all";
+@import "node_modules/govuk-frontend/govuk/objects/all";
+
+@import "node_modules/govuk-frontend/govuk/components/button";
+@import "node_modules/govuk-frontend/govuk/components/footer";
+@import "node_modules/govuk-frontend/govuk/components/header";
+```
+
 ### Fixes
 
 - [Pull request #1753: Make back link arrow consistent with breadcrumb component](https://github.com/alphagov/govuk-frontend/pull/1753)

src/govuk/_base.scss

@@ -0,0 +1,3 @@
+@import "settings/all";
+@import "tools/all";
+@import "helpers/all";

src/govuk/all.scss

@@ -1,6 +1,4 @@
-@import "settings/all";
-@import "tools/all";
-@import "helpers/all";
+@import "base";
 
 @import "core/all";
 @import "objects/all";

src/govuk/components/_all.scss

@@ -1,29 +1,31 @@
-@import "accordion/accordion";
-@import "back-link/back-link";
-@import "breadcrumbs/breadcrumbs";
-@import "button/button";
-@import "checkboxes/checkboxes";
-@import "character-count/character-count";
-@import "summary-list/summary-list";
-@import "date-input/date-input";
-@import "details/details";
-@import "error-message/error-message";
-@import "error-summary/error-summary";
-@import "fieldset/fieldset";
-@import "file-upload/file-upload";
-@import "footer/footer";
-@import "hint/hint";
-@import "header/header";
-@import "input/input";
-@import "inset-text/inset-text";
-@import "label/label";
-@import "panel/panel";
-@import "phase-banner/phase-banner";
-@import "tabs/tabs";
-@import "tag/tag";
-@import "radios/radios";
-@import "select/select";
-@import "skip-link/skip-link";
-@import "table/table";
-@import "textarea/textarea";
-@import "warning-text/warning-text";
+@import "../base";
+
+@import "accordion/index";
+@import "back-link/index";
+@import "breadcrumbs/index";
+@import "button/index";
+@import "checkboxes/index";
+@import "character-count/index";
+@import "summary-list/index";
+@import "date-input/index";
+@import "details/index";
+@import "error-message/index";
+@import "error-summary/index";
+@import "fieldset/index";
+@import "file-upload/index";
+@import "footer/index";
+@import "hint/index";
+@import "header/index";
+@import "input/index";
+@import "inset-text/index";
+@import "label/index";
+@import "panel/index";
+@import "phase-banner/index";
+@import "tabs/index";
+@import "tag/index";
+@import "radios/index";
+@import "select/index";
+@import "skip-link/index";
+@import "table/index";
+@import "textarea/index";
+@import "warning-text/index";

src/govuk/components/accordion/_accordion.scss

@@ -1,208 +1,2 @@
-@import "../../settings/all";
-@import "../../tools/all";
-@import "../../helpers/all";
-
-
-@include govuk-exports("govuk/component/accordion") {
-
-  $govuk-accordion-link-colour: $govuk-link-colour;
-  $govuk-accordion-link-hover-colour: govuk-colour("light-blue");
-  $govuk-accordion-border-width: 3px;
-
-  .govuk-accordion {
-    @include govuk-responsive-margin(6, "bottom");
-  }
-
-  // Borders between accordion sections
-  .govuk-accordion__section {
-    padding-top: govuk-spacing(3);
-  }
-
-  .govuk-accordion__section-header {
-    padding-top: govuk-spacing(3);
-    padding-bottom: govuk-spacing(3);
-  }
-
-  .govuk-accordion__section-heading {
-    margin-top: 0; // Override browser default
-    margin-bottom: 0; // Override browser default
-  }
-
-  // Buttons within the sections don’t need default styling
-  .govuk-accordion__section-button {
-    @include govuk-font($size: 24, $weight: bold);
-    display: inline-block;
-    margin-bottom: 0;
-    padding-top: govuk-spacing(3);
-  }
-
-  .govuk-accordion__section-summary {
-    margin-top: govuk-spacing(2);
-    margin-bottom: 0;
-  }
-
-  // Remove the bottom margin from the last item inside the content
-  .govuk-accordion__section-content > :last-child {
-    margin-bottom: 0;
-  }
-
-  // JavaScript enabled
-  .js-enabled {
-
-    .govuk-accordion {
-      // Border at the bottom of the whole accordion
-      border-bottom: 1px solid $govuk-border-colour;
-    }
-
-    // Borders between accordion sections
-    .govuk-accordion__section {
-      padding-top: 0;
-    }
-
-    // Hide the body of collapsed sections
-    .govuk-accordion__section-content {
-      display: none;
-      @include govuk-responsive-padding(3, "top");
-      @include govuk-responsive-padding(3, "bottom");
-    }
-
-    // Show the body of expanded sections
-    .govuk-accordion__section--expanded .govuk-accordion__section-content {
-      display: block;
-    }
-
-    // This is styled to look like a link not a button
-    .govuk-accordion__open-all {
-      @include govuk-font($size: 16);
-      position: relative;
-      z-index: 1;
-      margin: 0;
-      padding: 0;
-      border-width: 0;
-      color: $govuk-link-colour;
-      background: none;
-      cursor: pointer;
-      -webkit-appearance: none;
-
-      @include govuk-link-common;
-      @include govuk-link-style-default;
-
-      // Remove default button focus outline in Firefox
-      &::-moz-focus-inner {
-        padding: 0;
-        border: 0;
-      }
-    }
-
-    // Section headers have a pointer cursor as an additional affordance
-    .govuk-accordion__section-header {
-      position: relative;
-      // Safe area on the right to avoid clashing with icon
-      padding-right: 40px;
-      border-top: 1px solid $govuk-border-colour;
-      color: $govuk-accordion-link-colour;
-      cursor: pointer;
-    }
-
-    // For devices that can't hover such as touch devices,
-    // remove hover state as it can be stuck in that state (iOS).
-    @media (hover: none) {
-      .govuk-accordion__section-header:hover {
-        border-top-color: $govuk-accordion-link-colour;
-        box-shadow: inset 0 $govuk-accordion-border-width 0 0 $govuk-accordion-link-colour;
-      }
-    }
-
-    // Buttons within the headers don’t need default styling
-    .govuk-accordion__section-button {
-      @include govuk-typography-common;
-      margin-top: 0;
-      margin-bottom: 0;
-      margin-left: 0;
-      padding: 0;
-      border-width: 0;
-      color: inherit;
-      background: none;
-      text-align: left;
-      cursor: pointer;
-      -webkit-appearance: none;
-
-      &:focus {
-        @include govuk-focused-text;
-      }
-
-      // Remove default button focus outline in Firefox
-      &::-moz-focus-inner {
-        padding: 0;
-        border: 0;
-      }
-    }
-
-    // Extend the touch area of the button to span the section header
-    .govuk-accordion__section-button:after {
-      content: "";
-      position: absolute;
-      top: 0;
-      right: 0;
-      bottom: 0;
-      left: 0;
-    }
-
-    .govuk-accordion__section-button:hover:not(:focus) {
-      text-decoration: underline;
-    }
-
-    // For devices that can't hover such as touch devices,
-    // remove hover state as it can be stuck in that state (iOS).
-    @media (hover: none) {
-      .govuk-accordion__section-button:hover {
-        text-decoration: none;
-      }
-    }
-
-    .govuk-accordion__controls {
-      text-align: right;
-    }
-
-    // Display an icon to the right of each header to indicate open/closed status,
-    // and as an additional affordance.
-    .govuk-accordion__icon {
-      position: absolute;
-      top: 50%;
-      right: 15px;
-      width: 16px;
-      height: 16px;
-      margin-top: -8px;
-    }
-
-    .govuk-accordion__icon:after,
-    .govuk-accordion__icon:before {
-      content: "";
-      box-sizing: border-box;
-      position: absolute;
-      top: 0;
-      right: 0;
-      bottom: 0;
-      left: 0;
-      width: 25%;
-      height: 25%;
-      margin: auto;
-      border: 2px solid transparent;
-      background-color: govuk-colour("black");
-    }
-
-    .govuk-accordion__icon:before {
-      width: 100%;
-    }
-
-    .govuk-accordion__icon:after {
-      height: 100%;
-    }
-
-    // Vertical bar should be hidden when section is open, to display a '-' icon
-    .govuk-accordion__section--expanded .govuk-accordion__icon:after {
-      content: " ";
-      display: none;
-    }
-  }
-}
+@import "../../base";
+@import "./index";