add markdown editor soft break support

src/components/Widgets/Markdown/MarkdownControl/VisualEditor/plugins.js

@@ -1,3 +1,4 @@
+import SlateSoftBreak from 'slate-soft-break';
 import EditList from 'slate-edit-list';
 import EditTable from 'slate-edit-table';
 
@@ -31,6 +32,8 @@ const SoftBreakOpts = {
 
 export const SoftBreakConfigured = SoftBreak(SoftBreakOpts);
 
+export const ParagraphSoftBreakConfigured = SlateSoftBreak({ onlyIn: ['paragraph'], shift: true });
+
 const BackspaceCloseBlock = (options = {}) => ({
   onKeyDown(e, data, state) {
     if (data.key != 'backspace') return;
@@ -82,6 +85,7 @@ export const EditTableConfigured = EditTable(EditTableOpts);
 
 const plugins = [
   SoftBreakConfigured,
+  ParagraphSoftBreakConfigured,
   BackspaceCloseBlockConfigured,
   EditListConfigured,
   EditTableConfigured,

src/components/Widgets/Markdown/serializers/index.js

@@ -110,26 +110,11 @@ import registry from '../../../../lib/registry';
  * Deserialize a Markdown string to an MDAST.
  */
 export const markdownToRemark = markdown => {
-
-  /**
-   * Disabling tokenizers allows us to turn off features within the Remark
-   * parser.
-   */
-  function disableTokenizers() {
-
-    /**
-     * Turn off soft breaks until we can properly support them across both
-     * editors.
-     */
-    pull(this.Parser.prototype.inlineMethods, 'break');
-  }
-
   /**
    * Parse the Markdown string input to an MDAST.
    */
   const parsed = unified()
     .use(markdownToRemarkPlugin, { fences: true, pedantic: true, commonmark: true })
-    .use(disableTokenizers)
     .parse(markdown);
 
   /**

src/components/Widgets/Markdown/serializers/remarkSlate.js

@@ -231,6 +231,16 @@ function convertNode(node, nodes) {
       return createBlock(slateType, nodes, { data });
     }
 
+    /**
+     * Breaks
+     *
+     * MDAST soft break nodes represent a trailing double space or trailing
+     * slash from a Markdown document. In Slate, these are simply transformed to
+     * line breaks within a text node.
+     */
+    case 'break': {
+      return createText('\n');
+    }
 
     /**
      * Thematic Breaks

src/components/Widgets/Markdown/serializers/slateRemark.js

@@ -1,4 +1,4 @@
-import { get, isEmpty, concat, without, flatten } from 'lodash';
+import { get, isEmpty, concat, without, flatten, flatMap, initial } from 'lodash';
 import u from 'unist-builder';
 
 /**
@@ -56,6 +56,24 @@ function processCodeMark(markTypes) {
 }
 
 
+/**
+ * Returns an array of one or more MDAST text nodes of the given type, derived
+ * from the text received. Certain transformations, such as line breaks, cause
+ * multiple nodes to be returned.
+ */
+function createTextNodes(text, type = 'html') {
+  /**
+   * Split the text string at line breaks, then map each substring to an array
+   * pair consisting of an MDAST text node followed by a break node. This will
+   * result in nested arrays, so we use `flatMap` to produce a flattened array,
+   * and `initial` to leave off the superfluous trailing break.
+   */
+  const brokenText = text.split('\n');
+  const toPair = str => [u(type, str), u('break')];
+  return initial(flatMap(brokenText, toPair));
+}
+
+
 /**
  * Wraps a text node in one or more mark nodes by placing the text node in an
  * array and using that as the `children` value of a mark node. The resulting
@@ -130,7 +148,7 @@ function convertTextNode(node) {
    * MDAST node.
    */
   if (!node.ranges) {
-    return u('html', node.text);
+    return createTextNodes(node.text);
   }
 
   /**
@@ -154,13 +172,13 @@ function convertTextNode(node) {
     /**
      * Create the base text node.
      */
-    const textNode = u(textNodeType, text);
+    const textNodes = createTextNodes(text, textNodeType);
 
     /**
      * Recursively wrap the base text node in the individual mark nodes, if
      * any exist.
      */
-    return wrapTextWithMarks(textNode, filteredMarkTypes);
+    return textNodes.map(textNode => wrapTextWithMarks(textNode, filteredMarkTypes));
   });
 
   /**