v3.0.0

This release is the culmination of a massive amount of work, resulting in some
new features and significantly stronger and more reliable WAI ARIA spec
compliance. Notably, the project has been migrated from Flow to Typescript, and
a full accessibility audit has been performed - revealing a few holes in our
compliance which have now been entirely addressed.

Thanks to everyone who has contributed to this release - and not just those who
have written code. Contribution by way of issues relating to spec compliance,
pull-request commentary, advice and assistance is all greatly appreciated.
Thanks also to the patient users who have endured an extended period without a
release while we made sure to get this 100% right! Release cadence should return
to normal again now.

Breaking Changes - Upgrade Guide:

1. Rename all of your AccordionItemTitle components to AccordionItemHeading
   and then nest an AccordionItemButton directly inside of each one. Note that
   in order for your Accordion to remain spec-compliant, you may not put any
   other children inside AccordionItemHeading.

   // Before:
   import { AccordionItemTitle } from 'react-accessible-accordion';
   
   const headingBefore = <AccordionItemTitle>Foo</AccordionItemTitle>;

   //  After:
   import {
       AcccordionItemHeading,
       AccordionItemButton,
   } from 'react-accessible-accordion';
   
   const headingAfter = (
       <AccordionItemHeading>
           <AccordionItemButton>Foo</AccordionItemButton>
       </AccordionItemHeading>
   );

2. Rename all of your AccordionItemBody components to AccordionItemPanel.

   // Before:
   import { AccordionItemBody } from 'react-accessible-accordion';
   
   const panelBefore = (
       <AccordionItemBody>
           Voluptate elit eiusmod laborum proident esse officia dolor laboris
           laboris amet nulla officia cillum.
       </AccordionItemBody>
   );

   // After:
   import { AccordionItemPanel } from 'react-accessible-accordion';
   
   const panelAfter = (
       <AccordionItemPanel>
           Voluptate elit eiusmod laborum proident esse officia dolor laboris
           laboris amet nulla officia cillum.
       </AccordionItemPanel>
   );

3. Remove all instances of hideBodyClassName. This prop is no longer valid, as
   AccordionItemPanel components are now hidden without additional styling. If
   you must have a different className prop when an item is collapsed, then
   you may leverage the new AccordionItemState component.

   // Before
   import { AccordionItemPanel } from 'react-accessible-accordion';
   
   const panelBefore = (
       <AccordionItemPanel className="foo" hideBodyClassName="foo--hidden" />
   );

   // After:
   import {
       AccordionItemPanel,
       AccordionItemState,
   } from 'react-accessible-accordion';
   
   const panelAfter = (
       <AccordionItemState>
           {({ expanded }) => (
               <AccordionItemPanel
                   className={expanded ? 'foo' : 'foo foo--hidden'}
               />
           )}
       </AccordionItemState>
   );

4. Remove all instances of AccordionItem’s expanded prop and instead use
   Accordion’s preExpanded prop. Note that this means that ‘controlled’
   accordions are no longer a supported pattern. Please raise an issue if you
   have a use-case which calls for the ability to manually control expanded
   state.

   // Before
   import { Accordion, AccordionItem } from 'react-accessible-accordion';
   
   const accordionBefore = (
       <Accordion>
           <AccordionItem expanded />
       </Accordion>
   );

   // After:
   import { Accordion, AccordionItem } from 'react-accessible-accordion';
   
   const accordionAfter = (
       <Accordion preExpanded={['foo']}>
           <AccordionItem uuid="foo" />
       </Accordion>
   );

5. Remove all instances of Accordion’s accordion prop. Instead, use a
   combination of allowZeroExpanded and allowMultipleExpanded props to suit
   your requirements. If you were not explicitly setting accordion to false
   then you probably are not required to make any changes here.

   // Before
   import { Accordion } from 'react-accessible-accordion';
   
   const accordionBefore = <Accordion accordion={false} />;

   // After:
   import { Accordion } from 'react-accessible-accordion';
   
   const accordionAfter = <Accordion allowMultipleExpanded />;

6. Upgrade to React v16.3+

7. Remove your minimal-example.css import. These styles only applied
   display: none to panels when collapsed, but browsers apply these styles to
   elements with the hidden attribute, which the AccordionItemPanel
   component now has (when collapsed).

Added

• Added AccordionItemButton component.
• Added AccordionItemState component.
• Added allowZeroExpanded prop to Accordion.
• Added allowMultipleExpanded prop to Accordion.
• Out-of-the-box Typescript support.
• Integration tests to explicitly assert every line of the WAI ARIA
  'Accordion' spec.
• Additional keyboard functionality (Up, Down, Left, Right, Home, End).

Changed

• Renamed AccordionItemTitle to AccordionItemHeading to be consistent with
  the language used in the WAI ARIA spec.
• Renamed AccordionItemBody to AccordionItemPanel to be consistent with
  the language used in the WAI ARIA spec.
• Updated AccordionItemPanel to have a hidden attribute.
• Roles and aria attributes all audited and updated to match the WAI ARIA
  spec.
• Update onChange to always be called with an array of the currently
  expanded items.

Fixed

• Fixes SSR (server-side rendering).
• Fixes incorrect roles and attributes as per the WAI ARIA spec.

Removed

• Removed Flow support (but we hope to reinstate typing in the future. Track
  progress
  here).
• Removed undocumented expanded mechanism for AccordionItems.
• Removed undocumented disabled mechanism for AccordionItems.
• Remove hideBodyClassName prop.