update sidebar styling, closes #48

src/components/ModuleLayout/SidebarNav/Accordion.tsx

@@ -0,0 +1,60 @@
+import * as React from 'react';
+import { useEffect, useState } from 'react';
+import styled from 'styled-components';
+import tw from 'twin.macro';
+import useStickyState from '../../../hooks/useStickyState';
+
+const Container = styled.div`
+  &:last-of-type {
+    ${tw`border-b`}
+  }
+`;
+
+const Label = styled.div`
+  &:hover {
+    background-color: #f7faff;
+  }
+`;
+
+export default function Accordion({ label, isActive, children }) {
+  const [expanded, setExpanded] = useStickyState(
+    true,
+    'guide:sidebarnav:isexpanded:' + label
+  );
+  useEffect(() => {
+    if (isActive) setExpanded(true);
+  }, [isActive]);
+  return (
+    <Container
+      className="border-t border-gray-200"
+      style={isActive ? { backgroundColor: '#f7faff' } : null}
+    >
+      <Label
+        className="font-medium cursor-pointer text-gray-600 relative flex items-center px-6 py-3 text-sm leading-5"
+        onClick={() => setExpanded(!expanded)}
+      >
+        <span className="flex-1">{label}</span>
+        <svg
+          className="h-5 w-5 flex-shrink-0 text-gray-600"
+          fill="currentColor"
+          viewBox="0 0 20 20"
+        >
+          {expanded ? (
+            <path
+              fillRule="evenodd"
+              d="M5.293 7.293a1 1 0 011.414 0L10 10.586l3.293-3.293a1 1 0 111.414 1.414l-4 4a1 1 0 01-1.414 0l-4-4a1 1 0 010-1.414z"
+              clipRule="evenodd"
+            />
+          ) : (
+            <path
+              fillRule="evenodd"
+              d="M7.293 14.707a1 1 0 010-1.414L10.586 10 7.293 6.707a1 1 0 011.414-1.414l4 4a1 1 0 010 1.414l-4 4a1 1 0 01-1.414 0z"
+              clipRule="evenodd"
+            />
+          )}
+        </svg>
+      </Label>
+      {expanded && children}
+    </Container>
+  );
+}

src/components/ModuleLayout/SidebarNav/ItemLink.tsx

@@ -1,6 +1,7 @@
 import * as React from 'react';
 import { Link } from 'gatsby';
 import { ModuleLinkInfo } from '../../../module';
+import StyledLink from './StyledLink';
 
 const ItemLink = ({
   link,
@@ -13,19 +14,15 @@ const ItemLink = ({
 
   React.useEffect(() => {
     if (isActive) {
-      console.log(itemRef);
       itemRef.current.scrollIntoView({ block: `center` });
     }
   }, [isActive]);
 
   return (
-    <Link
-      to={link.url}
-      className={`flex items-center px-6 py-3 text-sm leading-5 text-gray-600 hover:text-gray-900 hover:bg-gray-100 focus:outline-none focus:bg-gray-200 transition ease-in-out duration-150`}
-      key={link.url}
-      ref={itemRef}
-    >
-      {link.title}
+    <Link to={link.url} key={link.url}>
+      <StyledLink isActive={isActive} ref={itemRef}>
+        {link.title}
+      </StyledLink>
     </Link>
   );
 };

src/components/ModuleLayout/SidebarNav/SidebarNav.tsx

@@ -2,6 +2,7 @@ import * as React from 'react';
 import { ModuleLinkInfo } from '../../../module';
 import { Link } from 'gatsby';
 import ItemLink from './ItemLink';
+import Accordion from './Accordion';
 
 export interface NavLinkGroup {
   label: string;
@@ -23,18 +24,25 @@ export const SidebarNav = ({
   const renderLink = (link: NavLinkItem) => {
     if (link instanceof ModuleLinkInfo) {
       return (
-        <ItemLink key={link.url} link={link} isActive={link === activeLink} />
+        <ItemLink
+          key={link.url}
+          link={link}
+          isActive={link.id === activeLink.id}
+        />
       );
     }
     return (
-      <div className="bg-gray-100 mb-4" key={link.label}>
-        <div
-          className={`flex items-center px-6 py-3 text-sm leading-5 font-medium text-gray-600 border-b border-gray-200`}
-        >
-          {link.label}
-        </div>
+      <Accordion
+        key={link.label}
+        label={link.label}
+        isActive={
+          link.children.findIndex(
+            x => x instanceof ModuleLinkInfo && x.id === activeLink.id
+          ) !== -1
+        }
+      >
         {link.children.map(renderLink)}
-      </div>
+      </Accordion>
     );
   };
   return <>{links.map(renderLink)}</>;

src/components/ModuleLayout/SidebarNav/StyledLink.tsx

@@ -0,0 +1,52 @@
+import styled, { css } from 'styled-components';
+import tw from 'twin.macro';
+import { Link } from 'gatsby';
+
+// Almost entirely copy pasted from https://gatsbyjs.org/ oops
+
+const StyledLink = styled.span`
+  ${tw`focus:outline-none transition ease-in-out duration-150 hover:text-blue-700 focus:bg-blue-100 relative flex items-center px-6 py-3 text-sm leading-5`}
+
+  ${({ isActive }) =>
+    isActive
+      ? tw`text-blue-700 font-semibold`
+      : tw`text-gray-600`}
+  
+
+      &::before,
+      &::after {
+    content: '';
+    left: 0.5rem;
+    top: 1.3em;
+    height: 8px;
+    width: 8px;
+    position: absolute;
+    transition: all 250ms cubic-bezier(0.4, 0, 0.2, 1) 0s;
+  }
+
+  ${props =>
+    props.isActive &&
+    css`
+      &::after {
+        transform: ${props =>
+          props.isActive ? 'translateX(-92px)' : 'translateX(-100px)'};
+        width: 100px;
+        border-radius: 4px;
+        ${tw`bg-blue-600`}
+      }
+    `}
+
+  &::before {
+    transform: scale(0.1);
+    border-radius: 100%;
+  }
+
+  &:hover {
+    &::before {
+      transform: scale(1);
+      ${tw`bg-blue-600`}
+    }
+  }
+`;
+
+export default StyledLink;

src/components/markdown/LanguageSection.tsx

@@ -29,10 +29,10 @@ export const LanguageSection = props => {
     return (
       <>
         {Object.keys(sections).map(lang => (
-          <>
+          <div key={lang}>
             <p className="text-lg font-bold">{languages[lang]}</p>
             {sections[lang]}
-          </>
+          </div>
         ))}
       </>
     );