[Lens] add an accessible label to range slider (elastic#205308)

## Summary

Fixes elastic#182765 (with the solution
suggested by @1Copenut)

---------

Co-authored-by: kibanamachine <[email protected]>

Author: mbondyra

x-pack/platform/packages/private/kbn-random-sampling/src/ui/slider_control/index.test.tsx

@@ -10,13 +10,42 @@ import React from 'react';
 import { I18nProvider } from '@kbn/i18n-react';
 import { ControlSlider } from '.';
 
+const values = [
+  {
+    label: '.001%',
+    value: 0.00001,
+    accessibleLabel: 'Point zero zero one percent, most performant',
+  },
+  {
+    label: '.01%',
+    value: 0.0001,
+  },
+  {
+    label: '.1%',
+    value: 0.001,
+  },
+  {
+    label: '1%',
+    value: 0.01,
+  },
+  {
+    label: '10%',
+    value: 0.1,
+  },
+  {
+    label: '100%',
+    value: 1,
+    accessibleLabel: 'One hundred percent, most accurate',
+  },
+];
+
 describe('Slider Control', () => {
   it('should basically work', () => {
     render(
       <I18nProvider>
         <ControlSlider
-          values={[0.1, 1]}
-          currentValue={0.1}
+          values={values}
+          currentValue={0.00001}
           onChange={jest.fn()}
           data-test-subj="test-id"
         />
@@ -26,18 +55,35 @@ describe('Slider Control', () => {
     expect(input.value).toBe('0'); // index 0 of the values array
   });
 
+  it('should display accessible label when provided', () => {
+    render(
+      <I18nProvider>
+        <ControlSlider
+          values={values}
+          currentValue={0.00001}
+          onChange={jest.fn()}
+          data-test-subj="test-id"
+        />
+      </I18nProvider>
+    );
+    const input = screen.getByTestId('test-id') as HTMLInputElement;
+    expect(input.getAttribute('aria-valuetext')).toBe(
+      '0, (Point zero zero one percent, most performant)'
+    );
+  });
+
   it('should fallback to 1 when the provided value is not present within the values', () => {
     render(
       <I18nProvider>
         <ControlSlider
-          values={[0.1, 0.5, 1]}
-          currentValue={2}
+          values={values}
+          currentValue={4}
           onChange={jest.fn()}
           data-test-subj="test-id"
         />
       </I18nProvider>
     );
     const input = screen.getByTestId('test-id') as HTMLInputElement;
-    expect(input.value).toBe('2'); // index 2 of the values array
+    expect(input.value).toBe('5'); // index 5 of the values array
   });
 });

x-pack/platform/packages/private/kbn-random-sampling/src/ui/slider_control/index.tsx

@@ -9,10 +9,11 @@ import { EuiFlexGroup, EuiFlexItem, EuiRange, EuiText, useEuiTheme } from '@elas
 import React from 'react';
 import { FormattedMessage } from '@kbn/i18n-react';
 import { TooltipWrapper } from '@kbn/visualization-utils';
+import { i18n } from '@kbn/i18n';
 
 export interface ControlSliderProps {
   /** Allowed values to show on the Control Slider */
-  values: number[];
+  values: Array<{ label: string; value: number; accessibleLabel?: string }>;
   /** Current value set */
   currentValue: number | undefined;
   /** When set will show the control in a disabled state */
@@ -34,8 +35,10 @@ export function ControlSlider({
   'data-test-subj': dataTestSubj,
 }: ControlSliderProps) {
   const { euiTheme } = useEuiTheme();
-  const samplingIndex = values.findIndex((v) => v === currentValue);
+
+  const samplingIndex = values.findIndex((v) => v.value === currentValue);
   const currentSamplingIndex = samplingIndex > -1 ? samplingIndex : values.length - 1;
+
   return (
     <TooltipWrapper
       tooltipContent={disabledReason}
@@ -58,22 +61,28 @@ export function ControlSlider({
         <EuiFlexItem>
           <EuiRange
             data-test-subj={dataTestSubj}
+            aria-label={i18n.translate('randomSampling.ui.sliderControl.ariaLabel', {
+              defaultMessage: 'Sampling percentages',
+            })}
+            aria-describedby={i18n.translate('randomSampling.ui.sliderControl.ariaDescribedby', {
+              defaultMessage:
+                'Lower sampling percentages increases the performance, but lowers the accuracy. Lower sampling percentages are best for large datasets.',
+            })}
             value={currentSamplingIndex}
             disabled={disabled}
             fullWidth
             onChange={(e) => {
-              onChange(values[Number(e.currentTarget.value)]);
+              onChange(values[Number(e.currentTarget.value)].value);
             }}
             showInput={false}
             showRange={false}
             showTicks
             step={1}
             min={0}
             max={values.length - 1}
-            ticks={values.map((v, i) => ({
-              // Remove the initial 0 from values with decimal digits: 0.001 => .001
-              label: `${v * 100}%`.slice(Number.isInteger(v * 100) ? 0 : 1),
-              value: i,
+            ticks={values.map((tick, index) => ({
+              ...tick,
+              value: index,
             }))}
           />
         </EuiFlexItem>

x-pack/platform/packages/private/kbn-random-sampling/tsconfig.json

@@ -14,6 +14,7 @@
   "kbn_references": [
     "@kbn/i18n-react",
     "@kbn/visualization-utils",
+    "@kbn/i18n",
   ],
   "exclude": [
     "target/**/*",

x-pack/platform/plugins/shared/lens/public/datasources/form_based/layer_settings.tsx

@@ -17,7 +17,41 @@ import { IgnoreGlobalFilterRowControl } from '../../shared_components/ignore_glo
 import { trackUiCounterEvents } from '../../lens_ui_telemetry';
 import { ExperimentalBadge } from '../../shared_components';
 
-const samplingValues = [0.00001, 0.0001, 0.001, 0.01, 0.1, 1];
+const samplingValues = [
+  {
+    label: '.001%',
+    value: 0.00001,
+    accessibleLabel: i18n.translate(
+      'xpack.lens.randomSampling.ui.sliderControl.tickLabels.0.00001',
+      {
+        defaultMessage: 'Point zero zero one percent, most performant',
+      }
+    ),
+  },
+  {
+    label: '.01%',
+    value: 0.0001,
+  },
+  {
+    label: '.1%',
+    value: 0.001,
+  },
+  {
+    label: '1%',
+    value: 0.01,
+  },
+  {
+    label: '10%',
+    value: 0.1,
+  },
+  {
+    label: '100%',
+    value: 1,
+    accessibleLabel: i18n.translate('xpack.lens.randomSampling.ui.sliderControl.tickLabels.1', {
+      defaultMessage: 'One hundred percent, most accurate',
+    }),
+  },
+];
 
 export function LayerSettingsPanel({
   state,
@@ -26,7 +60,7 @@ export function LayerSettingsPanel({
 }: DatasourceLayerSettingsProps<FormBasedPrivateState>) {
   const isSamplingValueDisabled = !isSamplingValueEnabled(state.layers[layerId]);
   const currentValue = isSamplingValueDisabled
-    ? samplingValues[samplingValues.length - 1]
+    ? samplingValues[samplingValues.length - 1].value
     : state.layers[layerId].sampling;
 
   return (