title: Select MenuItem doesn't show when JSX saved to state
body: <p>Working from the demo here: <a href="https://material-ui.com/demos/selects/" rel="nofollow noreferrer">https://material-ui.com/demos/selects/</a> and I'm receiving some weird results.  Specifically, when I select an item from the drop-down menu, the <code>this.props.value</code> updates fine... but the MenuItem does not show up.</p>
  
  <p>If I put the <code>&lt;FormControl&gt;</code> tag directly in render, it works fine.  If I put in an a variable, then setState with that and insert that into the render... it does NOT work.</p>
  
  <p>Example:</p>
  
  <pre><code>import React from 'react';
  import PropTypes from 'prop-types';
  import { withStyles } from '@material-ui/core/styles';
  import InputLabel from '@material-ui/core/InputLabel';
  import MenuItem from '@material-ui/core/MenuItem';
  import FormControl from '@material-ui/core/FormControl';
  import Select from '@material-ui/core/Select';
  
  const styles = theme =&gt; ({
      root: {
          display: 'flex',
          flexWrap: 'wrap',
      },
      formControl: {
          margin: theme.spacing.unit,
          minWidth: 120,
      },
      selectEmpty: {
          marginTop: theme.spacing.unit * 2,
      },
  });
  
  class Question extends React.Component {
      state = {
          age: '',
          age2: '',
          slct: ''
      };
  
      componentDidMount() {
          const { classes } = this.props;
          var mySelect =
              &lt;FormControl className={classes.formControl}&gt;
                  &lt;InputLabel htmlFor="age-simple"&gt;Age&lt;/InputLabel&gt;
                  &lt;Select
                      value={this.state.age}
                      onChange={this.handleChange}
                      inputProps={{
                          name: 'age',
                          id: 'age-simple',
                      }}
                  &gt;
                      &lt;MenuItem value=""&gt;
                          &lt;em&gt;None&lt;/em&gt;
                      &lt;/MenuItem&gt;
                      &lt;MenuItem value={10}&gt;Ten&lt;/MenuItem&gt;
                      &lt;MenuItem value={20}&gt;Twenty&lt;/MenuItem&gt;
                      &lt;MenuItem value={30}&gt;Thirty&lt;/MenuItem&gt;
                  &lt;/Select&gt;
              &lt;/FormControl&gt;
          this.setState({ slct: mySelect });
      }
  
      handleChange = event =&gt; {
          this.setState({ [event.target.name]: event.target.value });
      };
  
  
      render() {
          const { classes } = this.props;
          return (
              &lt;div&gt;
                  {this.state.slct}
                  &lt;p&gt;Value:&lt;/p&gt;{this.state.age}
  
                  &lt;FormControl className={classes.formControl}&gt;
                      &lt;InputLabel htmlFor="age-simple2"&gt;Age&lt;/InputLabel&gt;
                      &lt;Select
                          value={this.state.age2}
                          onChange={this.handleChange}
                          inputProps={{
                              name: 'age2',
                              id: 'age-simple2',
                          }}
                      &gt;
                          &lt;MenuItem value=""&gt;
                              &lt;em&gt;None&lt;/em&gt;
                          &lt;/MenuItem&gt;
                          &lt;MenuItem value={10}&gt;Ten&lt;/MenuItem&gt;
                          &lt;MenuItem value={20}&gt;Twenty&lt;/MenuItem&gt;
                          &lt;MenuItem value={30}&gt;Thirty&lt;/MenuItem&gt;
                      &lt;/Select&gt;
                  &lt;/FormControl&gt;
                  &lt;p&gt;Value:&lt;/p&gt;{this.state.age2}
  
              &lt;/div&gt;
          );
      }
  }
  
  export default withStyles(styles)(Question);
  </code></pre>
  
  <p>You can see how the 'value' updates correctly for both based on which answer I select in the drop down... but visually, the MenuItem label never appears to show up for the one that's coming from state:
  <a href="https://i.stack.imgur.com/6dijg.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/6dijg.png" alt="enter image description here"></a></p>
  
  <p>Help?</p>
  
  <p>(fyi: these items are in a parents' <code>&lt;form&gt;</code>.)</p>