Add support for Markdown styles expansion on pressing return

lib/components/DraftailEditor.js

@@ -490,9 +490,8 @@ class DraftailEditor extends Component<Props, State> {
 
   /* :: handleReturn: (e: SyntheticKeyboardEvent<>) => 'not-handled' | 'handled'; */
   handleReturn(e: SyntheticKeyboardEvent<>) {
-    const { enableLineBreak } = this.props;
+    const { enableLineBreak, inlineStyles } = this.props;
     const { editorState } = this.state;
-    const contentState = editorState.getCurrentContent();
     let ret = NOT_HANDLED;
 
     // alt + enter opens links and other entities with a `url` property.
@@ -504,7 +503,8 @@ class DraftailEditor extends Component<Props, State> {
       const entityKey = DraftUtils.getSelectionEntity(editorState);
 
       if (entityKey) {
-        const entityData = contentState.getEntity(entityKey).getData();
+        const content = editorState.getCurrentContent();
+        const entityData = content.getEntity(entityKey).getData();
 
         if (entityData.url) {
           window.open(entityData.url);
@@ -518,7 +518,34 @@ class DraftailEditor extends Component<Props, State> {
 
       let newState = editorState;
 
-      newState = DraftUtils.handleNewLine(newState, e);
+      const selection = newState.getSelection();
+      // Check whether we should apply a Markdown styles shortcut.
+      if (selection.isCollapsed()) {
+        const block = DraftUtils.getSelectedBlock(editorState);
+        const newStyle = behavior.handleBeforeInputInlineStyle(
+          block.getText(),
+          inlineStyles,
+        );
+
+        if (newStyle) {
+          newState = DraftUtils.applyMarkdownStyle(newState, newStyle, "");
+        }
+
+        const newLineState = DraftUtils.handleNewLine(newState, e);
+
+        // Manually handle the return if there is a style to apply.
+        if (!newLineState && newStyle) {
+          const content = newState.getCurrentContent();
+          const newContent = Modifier.splitBlock(content, selection);
+          newState = EditorState.push(newState, newContent, "split-block");
+          // Do not propagate the style from the last block.
+          newState = RichUtils.toggleInlineStyle(newState, newStyle.type);
+        } else {
+          newState = newLineState;
+        }
+      } else {
+        newState = DraftUtils.handleNewLine(newState, e);
+      }
 
       if (newState && newState !== editorState) {
         ret = HANDLED;
@@ -601,7 +628,6 @@ class DraftailEditor extends Component<Props, State> {
         );
       }
 
-      // TODO Do it on return as well.
       const newStyle = behavior.handleBeforeInputInlineStyle(
         beforeInput,
         inlineStyles,