[Collapse] Deprecate default prop `appear`

src/Collapse/Collapse.js

@@ -103,6 +103,7 @@ class Collapse extends React.Component {
 
   render() {
     const {
+      appear = false,
       children,
       classes,
       className,
@@ -121,6 +122,7 @@ class Collapse extends React.Component {
 
     return (
       <Transition
+        appear={appear}
         onEnter={this.handleEnter}
         onEntered={this.handleEntered}
         onEntering={this.handleEntering}
@@ -166,7 +168,20 @@ Collapse.propTypes = {
   /**
    * Déclenche une transition lorsque le composant est monté
    */
-  appear: PropTypes.bool,
+  appear: (props, propName, componentName, location, propFullName) => {
+    const componentNameSafe = componentName || '<<anonymous>>';
+    const propFullNameSafe = propFullName || propName;
+
+    if (typeof props[propName] === 'undefined') {
+      return new Error(
+        `The default value of ${location} \`${propFullNameSafe}\` of ` +
+          `\`${componentNameSafe}\` and will change to \`true\` in v2.0. ` +
+          `Explicitly set the value to turn off this warning.`
+      );
+    }
+
+    return null;
+  },
 
   /**
    * Contenu du composant

src/Collapse/demos/DynamicProps.js

@@ -82,6 +82,7 @@ class DynamicProps extends Component {
         </div>
         <div className={classes.wrapper}>
           <Collapse
+            appear={false}
             duration={{
               enter: durationEnter,
               exit: durationExit
@@ -91,6 +92,7 @@ class DynamicProps extends Component {
             <div className={classes.box}>Play with me !</div>
           </Collapse>
           <Collapse
+            appear={false}
             duration={{
               enter: durationEnter,
               exit: durationExit

src/List/demos/NestedList.js

@@ -60,7 +60,7 @@ class NestedList extends Component {
             <MdKeyboardArrowDown />
           </ListItemIcon>
         </ListItem>
-        <Collapse in={!collapsed} duration='auto'>
+        <Collapse appear={false} in={!collapsed} duration='auto'>
           <List>
             <ListItem>
               <ListItemText>Une autre liste...</ListItemText>