[Data Liberation] Build Markdown importer as phar

Builds data-liberation-markdown.phar.gz (200KB) to enable downloading the
Markdown importer only when needed instead of on every page load.

A part of:

* #2080
* #1894

 ## Testing instructions

Run `nx build playground-data-liberation-markdown`, confirm it finished
without errors. A smoke test of the built phar file is included in the
build command.

packages/playground/data-liberation-markdown/project.json

@@ -0,0 +1,45 @@
+{
+	"name": "playground-data-liberation-markdown",
+	"$schema": "../../../node_modules/nx/schemas/project-schema.json",
+	"sourceRoot": "packages/playground/data-liberation-markdown",
+	"projectType": "library",
+	"targets": {
+		"install": {
+			"executor": "nx:run-commands",
+			"options": {
+				"cwd": "packages/playground/data-liberation-markdown",
+				"commands": ["composer install"],
+				"parallel": false
+			}
+		},
+		"build:phar": {
+			"executor": "nx:run-commands",
+			"options": {
+				"cwd": "packages/playground/data-liberation-markdown",
+				"commands": ["bash ./phar-build.sh"],
+				"parallel": false
+			},
+			"dependsOn": ["playground-data-liberation:build:phar"]
+		},
+		"lint:php": {
+			"executor": "nx:run-commands",
+			"options": {
+				"cwd": "packages/playground/data-liberation-markdown",
+				"commands": [
+					"../data-liberation/vendor/bin/phpcs --standard=./phpcs.xml -s ./src ./*.php"
+				],
+				"parallel": false
+			}
+		},
+		"lint:php:fix": {
+			"executor": "nx:run-commands",
+			"options": {
+				"cwd": "packages/playground/data-liberation-markdown",
+				"commands": [
+					"../data-liberation/vendor/bin/phpcbf --standard=./phpcs.xml ./src"
+				],
+				"parallel": false
+			}
+		}
+	}
+}

packages/playground/data-liberation-markdown/src/WP_Markdown_Importer.php

@@ -8,14 +8,14 @@ public static function create_for_markdown_directory( $markdown_directory, $opti
 		return WP_Markdown_Importer::create(
 			function ( $cursor = null ) use ( $markdown_directory ) {
 				// @TODO: Handle $cursor
-				return new WP_Directory_Tree_Entity_Reader( 
+				return new WP_Directory_Tree_Entity_Reader(
 					new WP_Filesystem(),
-					array (
+					array(
 						'root_dir' => $markdown_directory,
 						'first_post_id' => 1,
 						'allowed_extensions' => array( 'md' ),
 						'index_file_patterns' => array( '#^index\.md$#' ),
-						'markup_converter_factory' => function( $content ) {
+						'markup_converter_factory' => function ( $content ) {
 							return new WP_Markdown_To_Blocks( $content );
 						},
 					)
@@ -42,7 +42,7 @@ protected static function parse_options( $options ) {
 			return false;
 		}
 		$options['local_markdown_assets_root'] = rtrim( $options['local_markdown_assets_root'], '/' );
-		
+
 		return parent::parse_options( $options );
 	}
 

packages/playground/data-liberation-markdown/src/WP_Markdown_To_Blocks.php

@@ -80,10 +80,10 @@ private function convert_markdown_to_blocks() {
 		$parser = new MarkdownParser( $environment );
 
 		$document          = $parser->parse( $this->markdown );
-		$this->frontmatter = [];
-		foreach( $document->data as $key => $value ) {
+		$this->frontmatter = array();
+		foreach ( $document->data as $key => $value ) {
 			// Use an array as a value to comply with the WP_Block_Markup_Converter interface.
-			$this->frontmatter[ $key ] = [$value];
+			$this->frontmatter[ $key ] = array( $value );
 		}
 
 		$walker = $document->walker();

packages/playground/data-liberation-markdown/src/bootstrap.php

@@ -3,4 +3,4 @@
 require_once __DIR__ . '/WP_Markdown_Importer.php';
 require_once __DIR__ . '/WP_Markdown_To_Blocks.php';
 
-require_once __DIR__ . '/../vendor/autoload.php';
+require_once __DIR__ . '/../vendor/autoload.php';

packages/playground/data-liberation/bootstrap.php

@@ -44,6 +44,7 @@
 	require_once __DIR__ . '/src/wordpress-core-html-api/html5-named-character-references.php';
 }
 
+require_once __DIR__ . '/src/block-markup/WP_Block_Markup_Converter.php';
 require_once __DIR__ . '/src/block-markup/WP_Block_Markup_Processor.php';
 require_once __DIR__ . '/src/block-markup/WP_Block_Markup_Url_Processor.php';
 require_once __DIR__ . '/src/block-markup/WP_URL_In_Text_Processor.php';
@@ -63,7 +64,6 @@
 require_once __DIR__ . '/src/import/WP_Stream_Importer.php';
 require_once __DIR__ . '/src/import/WP_Entity_Iterator_Chain.php';
 require_once __DIR__ . '/src/import/WP_Retry_Frontloading_Iterator.php';
-require_once __DIR__ . '/src/import/WP_Markdown_Importer.php';
 
 require_once __DIR__ . '/src/utf8_decoder.php';
 

packages/playground/data-liberation/src/block-markup/WP_Block_Markup_Converter.php

@@ -0,0 +1,8 @@
+<?php
+
+interface WP_Block_Markup_Converter {
+	public function convert();
+	public function get_block_markup();
+	public function get_all_metadata();
+	public function get_meta_value( $key );
+}