feat(select): add helper text (#824)

packages/select/helper-text/README.md

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+# React Select Helper Text
+
+MDC React Select Helper Text is a React Component which uses MDC [MDC Select Helper Text](https://github.com/material-components/material-components-web/tree/master/packages/mdc-select/helper-text/)'s CSS and foundation JavaScript.
+
+## Usage
+
+```js
+import {SelectHelperText} from '@material/react-select/helper-text/index';
+
+const MyComponent = () => {
+  return (
+    <SelectHelperText>
+      Really fun helper text
+    </SelectHelperText>
+  );
+}
+```
+
+## Props
+
+Prop Name | Type | Description
+--- | --- | ---
+persistent | boolean | Adds the `.mdc-select-helper-text--persistent` class to keep the helper text always visible.

packages/select/helper-text/index.tsx

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+// The MIT License
+//
+// Copyright (c) 2019 Google, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+import * as React from 'react';
+import classnames from 'classnames';
+import {MDCSelectHelperTextAdapter} from '@material/select/helper-text/adapter';
+import {MDCSelectHelperTextFoundation} from '@material/select/helper-text/foundation';
+
+export interface SelectHelperTextProps extends React.HTMLProps<HTMLParagraphElement> {
+  persistent?: boolean;
+  setHelperTextFoundation?: (foundation?: MDCSelectHelperTextFoundation) => void;
+}
+
+interface ElementAttributes {
+  'aria-hidden'?: boolean | 'false' | 'true';
+  role?: string;
+};
+
+interface SelectHelperTextState extends ElementAttributes {
+  classList: Set<string>;
+};
+
+export class SelectHelperText extends React.Component<SelectHelperTextProps, SelectHelperTextState> {
+  foundation?: MDCSelectHelperTextFoundation;
+
+  state: SelectHelperTextState = {
+    'aria-hidden': undefined,
+    'role': undefined,
+    'classList': new Set(),
+  };
+
+  componentDidMount() {
+    const {setHelperTextFoundation} = this.props;
+    this.foundation = new MDCSelectHelperTextFoundation(this.adapter);
+    this.foundation.init();
+    setHelperTextFoundation && setHelperTextFoundation(this.foundation);
+  }
+
+  componentWillUnmount() {
+    const {setHelperTextFoundation} = this.props;
+    if (this.foundation) {
+      this.foundation.destroy();
+      setHelperTextFoundation && setHelperTextFoundation(undefined);
+    }
+  }
+
+  get classes() {
+    const {className, persistent} = this.props;
+    const {classList} = this.state;
+    return classnames('mdc-select-helper-text', Array.from(classList), className, {
+      'mdc-select-helper-text--persistent': persistent,
+    });
+  }
+
+  get adapter(): MDCSelectHelperTextAdapter {
+    return {
+      addClass: (className: string) => {
+        const classList = new Set(this.state.classList);
+        classList.add(className);
+        this.setState({classList});
+      },
+      removeClass: (className: string) => {
+        const classList = new Set(this.state.classList);
+        classList.delete(className);
+        this.setState({classList});
+      },
+      hasClass: (className: string) => {
+        return this.classes.split(' ').includes(className);
+      },
+      setAttr: (attr: keyof ElementAttributes, value: ElementAttributes[keyof ElementAttributes]) => {
+        this.setState((prevState) => ({
+          ...prevState,
+          [attr]: value,
+        }));
+      },
+      removeAttr: (attr: keyof ElementAttributes) => {
+        this.setState((prevState) => ({...prevState, [attr]: null}));
+      },
+      setContent: () => {
+        // not implmenting because developer should would never call `setContent()`
+      },
+    };
+  }
+
+  render() {
+    const {
+      children,
+      /* eslint-disable no-unused-vars */
+      persistent,
+      className,
+      setHelperTextFoundation,
+      /* eslint-enable no-unused-vars */
+      ...otherProps
+    } = this.props;
+    const {
+      'aria-hidden': ariaHidden,
+      role,
+    } = this.state;
+
+    return (
+      <p
+        className={this.classes}
+        aria-hidden={ariaHidden}
+        role={role}
+        {...otherProps}
+      >
+        {children}
+      </p>
+    );
+  }
+}

test/unit/select/helper-text/index.test.tsx

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+import * as React from 'react';
+import * as td from 'testdouble';
+import {assert} from 'chai';
+import {shallow, mount} from 'enzyme';
+import {SelectHelperText} from '../../../../packages/select/helper-text/index';
+import {MDCSelectHelperTextFoundation} from '@material/select/helper-text/foundation';
+
+suite('Select Helper Text');
+
+test('renders with mdc-select-helper-text class', () => {
+  const wrapper = shallow(<SelectHelperText />);
+  assert.isTrue(wrapper.hasClass('mdc-select-helper-text'));
+});
+
+test('renders with a test class name', () => {
+  const wrapper = shallow(<SelectHelperText className='test-class' />);
+  assert.isTrue(wrapper.hasClass('test-class'));
+});
+
+test('renders with class from state.classList', () => {
+  const wrapper = shallow(<SelectHelperText />);
+  wrapper.setState({classList: new Set(['test-class'])});
+  assert.isTrue(wrapper.hasClass('test-class'));
+});
+
+test('renders with persistent class when props.persistent is true', () => {
+  const wrapper = shallow(<SelectHelperText persistent />);
+  assert.isTrue(wrapper.hasClass('mdc-select-helper-text--persistent'));
+});
+
+test.only('calls setHelperTextFoundation with foundation', () => {
+  const setHelperTextFoundation = td.func<(foundation?: MDCSelectHelperTextFoundation) => void>();
+  shallow(<SelectHelperText setHelperTextFoundation={setHelperTextFoundation} />);
+  // TODO: change Object to MDCSelectHelperTextFoundation in PR 823
+  td.verify(setHelperTextFoundation(td.matchers.isA(Object)), {times: 1});
+});
+
+test('#componentWillUnmount destroys foundation', () => {
+  const wrapper = mount<SelectHelperText>(<SelectHelperText />);
+  const foundation = wrapper.instance().foundation!;
+  foundation.destroy = td.func<() => void>();
+  wrapper.unmount();
+  td.verify(foundation.destroy(), {times: 1});
+});
+
+test('#adapter.addClass should add a class to state.classList', () => {
+  const wrapper = shallow<SelectHelperText>(<SelectHelperText />);
+  wrapper.instance().adapter.addClass('test-class');
+  assert.isTrue(wrapper.state().classList.has('test-class'));
+});
+
+test('#adapter.removeClass should remove a class to state.classList', () => {
+  const wrapper = shallow<SelectHelperText>(<SelectHelperText />);
+  wrapper.setState({classList: new Set(['test-class'])});
+  wrapper.instance().adapter.removeClass('test-class');
+  assert.isFalse(wrapper.state().classList.has('test-class'));
+});
+
+test('#adapter.hasClass should return true if state.classList has class', () => {
+  const wrapper = shallow<SelectHelperText>(<SelectHelperText />);
+  wrapper.setState({classList: new Set(['test-class'])});
+  assert.isTrue(wrapper.instance().adapter.hasClass('test-class'));
+});
+
+test('#adapter.hasClass should return true if className has class', () => {
+  const wrapper = shallow<SelectHelperText>(<SelectHelperText className='test-class' />);
+  assert.isTrue(wrapper.instance().adapter.hasClass('test-class'));
+});
+
+test('#adapter.setAttr should update state', () => {
+  const wrapper = shallow<SelectHelperText>(<SelectHelperText />);
+  wrapper.instance().adapter.setAttr('role', 'menu');
+  assert.equal(wrapper.state().role, 'menu');
+});
+
+test('#adapter.removeAttr should update state', () => {
+  const wrapper = shallow<SelectHelperText>(<SelectHelperText />);
+  wrapper.setState({role: 'menu'});
+  wrapper.instance().adapter.removeAttr('role');
+  assert.equal(wrapper.state().role, null);
+});
+
+test('renders with aria-hidden from state.aria-hidden', () => {
+  const wrapper = mount<SelectHelperText>(<SelectHelperText />);
+  wrapper.setState({'aria-hidden': 'true'});
+  assert.equal(wrapper.getDOMNode().getAttribute('aria-hidden'), 'true');
+});
+
+test('renders with role from state.role', () => {
+  const wrapper = mount<SelectHelperText>(<SelectHelperText />);
+  wrapper.setState({'role': 'true'});
+  assert.equal(wrapper.getDOMNode().getAttribute('role'), 'true');
+});
+
+test('renders children', () => {
+  const wrapper = mount<SelectHelperText>(<SelectHelperText>MEOW</SelectHelperText>);
+  assert.equal(wrapper.text(), 'MEOW');
+});