Expose the grammar parser to the mobile app (WordPress#7691)

* Expose `parse` to RN, use pre-generated post parser

* Offer RawHTML to fix warning during save()

Warning is:
"Warning: React.createElement: type is invalid -- expected a string (for
built-in components) or a class/function (for composite components) but
got: undefined."

* Run parse() testcases for the pre-generated parser too

* Move RawHTML() to base module to avoid duplication

* Generalize parseWithGrammar to avoid code duplication

H/T to @gziolo for providing the createParse() function.

* Follow codestyle and add dep block header

* Separate describe() for the parse() testcases

Author: hypest

blocks/api/index.native.js

@@ -1,6 +1,9 @@
 export {
 	createBlock,
 } from './factory';
+export {
+	default as parse,
+} from './parser';
 export {
 	default as serialize,
 	getBlockContent,

blocks/api/parser.js

@@ -14,7 +14,7 @@ import deprecated from '@wordpress/deprecated';
 /**
  * Internal dependencies
  */
-import { parse as grammarParse } from './post.pegjs';
+import { parse as grammarParse } from './post-parser';
 import { getBlockType, getUnknownTypeHandlerName } from './registration';
 import { createBlock } from './factory';
 import { isValidBlock } from './validation';
@@ -359,20 +359,28 @@ export function createBlockWithFallback( blockNode ) {
 }
 
 /**
- * Parses the post content with a PegJS grammar and returns a list of blocks.
+ * Creates a parse implementation for the post content which returns a list of blocks.
  *
- * @param {string} content The post content.
+ * @param {Function} parseImplementation Parse implementation.
  *
- * @return {Array} Block list.
+ * @return {Function} An implementation which parses the post content.
  */
-export function parseWithGrammar( content ) {
-	return grammarParse( content ).reduce( ( memo, blockNode ) => {
+export const createParse = ( parseImplementation ) =>
+	( content ) => parseImplementation( content ).reduce( ( memo, blockNode ) => {
 		const block = createBlockWithFallback( blockNode );
 		if ( block ) {
 			memo.push( block );
 		}
 		return memo;
 	}, [] );
-}
+
+/**
+ * Parses the post content with a PegJS grammar and returns a list of blocks.
+ *
+ * @param {string} content The post content.
+ *
+ * @return {Array} Block list.
+ */
+export const parseWithGrammar = createParse( grammarParse );
 
 export default parseWithGrammar;