From 941a5dca181c36db891bffd5abdbd7c83759a704 Mon Sep 17 00:00:00 2001
From: Jason Quense <monastic.panic@gmail.com>
Date: Mon, 20 Jul 2020 13:20:43 -0400
Subject: [PATCH] feat: add aria-describedby modifier for tooltips (#842)

* feat: add aria-describedby modifier for tooltips

* add test
---
 src/usePopper.ts      | 34 ++++++++++++++++++++-
 test/usePopperSpec.js | 70 ++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 99 insertions(+), 5 deletions(-)

diff --git a/src/usePopper.ts b/src/usePopper.ts
index 4edad3ad..05634231 100644
--- a/src/usePopper.ts
+++ b/src/usePopper.ts
@@ -59,6 +59,38 @@ export interface UsePopperState {
   state?: State;
 }
 
+const ariaDescribedByModifier: Modifier<'ariaDescribedBy', undefined> = {
+  name: 'ariaDescribedBy',
+  enabled: true,
+  phase: 'afterWrite',
+  effect: ({ state }) => {
+    return () => {
+      const { reference, popper } = state.elements;
+      if ('removeAttribute' in reference) {
+        const ids = (reference.getAttribute('aria-describedby') || '')
+          .split(',')
+          .filter((id) => id.trim() !== popper.id);
+
+        if (!ids.length) reference.removeAttribute('aria-describedby');
+        else reference.setAttribute('aria-describedby', ids.join(','));
+      }
+    };
+  },
+  fn: ({ state }) => {
+    const { popper, reference } = state.elements;
+
+    const role = popper.getAttribute('role')?.toLowerCase();
+
+    if (popper.id && role === 'tooltip' && 'setAttribute' in reference) {
+      const ids = reference.getAttribute('aria-describedby');
+      reference.setAttribute(
+        'aria-describedby',
+        ids ? `${ids},${popper.id}` : popper.id,
+      );
+    }
+  },
+};
+
 const EMPTY_MODIFIERS = [] as any;
 /**
  * Position an element relative some reference element using Popper.js
@@ -159,7 +191,7 @@ function usePopper(
       ...config,
       placement,
       strategy,
-      modifiers: [...modifiers, updateModifier],
+      modifiers: [...modifiers, ariaDescribedByModifier, updateModifier],
     });
 
     return () => {
diff --git a/test/usePopperSpec.js b/test/usePopperSpec.js
index 1c6fbea5..5dae5933 100644
--- a/test/usePopperSpec.js
+++ b/test/usePopperSpec.js
@@ -3,15 +3,16 @@ import React from 'react';
 import usePopper from '../src/usePopper';
 
 describe('usePopper', () => {
-  function renderHook(fn) {
+  function renderHook(fn, initialProps) {
     let result = { current: null };
 
-    function Wrapper() {
-      result.current = fn();
+    function Wrapper(props) {
+      result.current = fn(props);
       return null;
     }
 
-    result.mount = mount(<Wrapper />);
+    result.mount = mount(<Wrapper {...initialProps} />);
+    result.update = (props) => result.mount.setProps(props);
 
     return result;
   }
@@ -46,4 +47,65 @@ describe('usePopper', () => {
       done();
     });
   });
+
+  it('should add aria-describedBy for tooltips', (done) => {
+    elements.popper.setAttribute('role', 'tooltip');
+    elements.popper.setAttribute('id', 'example123');
+
+    const result = renderHook(() =>
+      usePopper(elements.reference, elements.popper),
+    );
+
+    setTimeout(() => {
+      expect(
+        document.querySelector('[aria-describedby="example123"]'),
+      ).to.equal(elements.reference);
+
+      result.mount.unmount();
+
+      expect(
+        document.querySelector('[aria-describedby="example123"]'),
+      ).to.equal(null);
+
+      done();
+    });
+  });
+
+  it('should add to existing describedBy', (done) => {
+    elements.popper.setAttribute('role', 'tooltip');
+    elements.popper.setAttribute('id', 'example123');
+    elements.reference.setAttribute('aria-describedby', 'foo, bar , baz ');
+
+    const result = renderHook(() =>
+      usePopper(elements.reference, elements.popper),
+    );
+
+    setTimeout(() => {
+      expect(
+        document.querySelector(
+          '[aria-describedby="foo, bar , baz ,example123"]',
+        ),
+      ).to.equal(elements.reference);
+
+      result.mount.unmount();
+
+      expect(
+        document.querySelector('[aria-describedby="foo, bar , baz "]'),
+      ).to.equal(elements.reference);
+
+      done();
+    });
+  });
+
+  it('should not aria-describedBy any other role', (done) => {
+    renderHook(() => usePopper(elements.reference, elements.popper));
+
+    setTimeout(() => {
+      expect(
+        document.querySelector('[aria-describedby="example123"]'),
+      ).to.equal(null);
+
+      done();
+    });
+  });
 });