Preserve block style when pasting plain text

Summary:
Preserve block style when pasting plain text. That would allow pasting into code blocks and lists and applying respective styles to new blocks.
That should work for any type of block: code, list, quote, heading...

Probably related github issues:

  - #1276
  - #1219

Reviewed By: sophiebits

Differential Revision: D5786405

fbshipit-source-id: 3c6d074b0c3fe200761164ec6c5ccf1a82df5072

src/component/handlers/edit/editOnPaste.js

@@ -22,6 +22,7 @@ var DataTransfer = require('DataTransfer');
 var DraftModifier = require('DraftModifier');
 var DraftPasteProcessor = require('DraftPasteProcessor');
 var EditorState = require('EditorState');
+var RichTextEditorUtil = require('RichTextEditorUtil');
 
 var getEntityKeyForSelection = require('getEntityKeyForSelection');
 var getTextContentFromFiles = require('getTextContentFromFiles');
@@ -64,8 +65,15 @@ function editOnPaste(editor: DraftEditor, e: SyntheticClipboardEvent<>): void {
             editorState.getSelection(),
           ),
         });
+        var currentBlockType = RichTextEditorUtil.getCurrentBlockType(
+          editorState,
+        );
 
-        var text = DraftPasteProcessor.processText(blocks, character);
+        var text = DraftPasteProcessor.processText(
+          blocks,
+          character,
+          currentBlockType,
+        );
         var fragment = BlockMapBuilder.createFromArray(text);
 
         var withInsertedText = DraftModifier.replaceWithFragment(
@@ -178,9 +186,12 @@ function editOnPaste(editor: DraftEditor, e: SyntheticClipboardEvent<>): void {
       ),
     });
 
+    var currentBlockType = RichTextEditorUtil.getCurrentBlockType(editorState);
+
     var textFragment = DraftPasteProcessor.processText(
       textBlocks,
       character,
+      currentBlockType,
     );
 
     var textMap = BlockMapBuilder.createFromArray(textFragment);

src/model/paste/DraftPasteProcessor.js

@@ -14,6 +14,7 @@
 'use strict';
 
 import type {DraftBlockRenderMap} from 'DraftBlockRenderMap';
+import type {DraftBlockType} from 'DraftBlockType';
 import type {EntityMap} from 'EntityMap';
 
 const CharacterMetadata = require('CharacterMetadata');
@@ -46,13 +47,14 @@ const DraftPasteProcessor = {
   processText(
     textBlocks: Array<string>,
     character: CharacterMetadata,
+    type: DraftBlockType,
   ): Array<ContentBlock> {
     return textBlocks.map(
       textLine => {
         textLine = sanitizeDraftText(textLine);
         return new ContentBlock({
           key: generateRandomKey(),
-          type: 'unstyled',
+          type,
           text: textLine,
           characterList: List(Repeat(character, textLine.length)),
         });