Allow any element to be rendered under Link (#921)

* Allow any element to be rendered under Link

* Use Children.only instead of Children.map

* Remove check for multiple children since we already throw at 2+

* Clean up variables

lib/link.js

@@ -11,8 +11,16 @@ export default class Link extends Component {
 
   static propTypes = {
     children: PropTypes.oneOfType([
-      PropTypes.string,
-      PropTypes.element
+      PropTypes.element,
+      (props, propName) => {
+        const value = props[propName]
+
+        if (typeof value === 'string') {
+          warnLink(`Warning: You're using a string directly inside <Link>. This usage has been deprecated. Please add an <a> tag as child of <Link>`)
+        }
+
+        return null
+      }
     ]).isRequired
   }
 
@@ -54,28 +62,24 @@ export default class Link extends Component {
   }
 
   render () {
-    const children = Children.map(this.props.children, (child) => {
-      const props = {
-        onClick: this.linkClicked
-      }
-
-      const isAnchor = child && child.type === 'a'
+    let { children } = this.props
+    // Deprecated. Warning shown by propType check. If the childen provided is a string (<Link>example</Link>) we wrap it in an <a> tag
+    if (typeof children === 'string') {
+      children = <a>{children}</a>
+    }
 
-      // if child does not specify a href, specify it
-      // so that repetition is not needed by the user
-      if (!isAnchor || !('href' in child.props)) {
-        props.href = this.props.as || this.props.href
-      }
+    // This will return the first child, if multiple are provided it will throw an error
+    const child = Children.only(children)
+    const props = {
+      onClick: this.linkClicked
+    }
 
-      if (isAnchor) {
-        return React.cloneElement(child, props)
-      } else {
-        warnLink(`Warning: Every Link must be the parent of an anchor, this pattern is deprecated. Please add an anchor inside the <Link>.`)
-        return <a {...props}>{child}</a>
-      }
-    })
+    // If child is an <a> tag and doesn't have a href attribute we specify it so that repetition is not needed by the user
+    if (child.type === 'a' && !('href' in child.props)) {
+      props.href = this.props.as || this.props.href
+    }
 
-    return children[0]
+    return React.cloneElement(child, props)
   }
 }