Add parsing and validation for block.json files

block-json/block.json

@@ -0,0 +1,34 @@
+{
+	"name": "my-plugin/notice",
+	"title": "Notice",
+	"category": "text",
+	"parent": [ "core/group" ],
+	"icon": "star",
+	"description": "Shows warning, error or success notices  ...",
+	"keywords": [ "alert", "message" ],
+	"textdomain": "my-plugin",
+	"attributes": {
+		"message": {
+			"type": "string",
+			"source": "html",
+			"selector": ".message"
+		}
+	},
+	"supports": {
+		"align": true,
+		"lightBlockWrapper": true
+	},
+	"styles": [
+		{ "name": "default", "label": "Default", "isDefault": true },
+		{ "name": "other", "label": "Other" }
+	],
+	"example": {
+		"attributes": {
+			"message": "This is a notice!"
+		}
+	},
+	"editorScript": "build/editor.js",
+	"script": "build/main.js",
+	"editorStyle": "build/editor.css",
+	"style": "build/style.css"
+}

block-json/class-parser.php

@@ -0,0 +1,174 @@
+<?php
+
+namespace WordPressdotorg\Plugin_Directory\Block_JSON;
+
+use WP_Error;
+
+defined( 'WPINC' ) || die();
+
+/**
+ * Class Parser
+ *
+ * @package WordPressdotorg\Plugin_Directory\Block_JSON
+ */
+class Parser {
+	/**
+	 * A location resource must be pointing to a file named this.
+	 *
+	 * @const string
+	 */
+	const REQUIRED_FILENAME = 'block.json';
+
+	/**
+	 * Parse the JSON content of a given resource into a PHP object.
+	 *
+	 * @param array $resource An associative array with one item where the key specifies the type of resource and the
+	 *                        value represents the resource as a string. Valid types are `url`, `file`, and `content`.
+	 *                        In this case, the value of `content` is expected to be a raw string of JSON, while the
+	 *                        other two are expected to be the location of a file containing the JSON.
+	 *
+	 * @return object|WP_Error An object if the parse was successful, otherwise a WP_Error.
+	 */
+	public static function parse( array $resource ) {
+		reset( $resource );
+		$type   = key( $resource );
+		$handle = current( $resource );
+
+		switch ( $type ) {
+			case 'url':
+				$content = self::extract_content_from_url( $handle );
+				break;
+			case 'file':
+				$content = self::extract_content_from_file( $handle );
+				break;
+			case 'content':
+				$content = $handle;
+				break;
+			default:
+				$content = new WP_Error(
+					'no_valid_resource',
+					__( 'No valid resource type was given.', 'wporg-plugins' )
+				);
+				break;
+		}
+
+		if ( is_wp_error( $content ) ) {
+			return $content;
+		}
+
+		return self::parse_content( $content );
+	}
+
+	/**
+	 * Get the contents of a block.json file via an HTTP request to a URL.
+	 *
+	 * @param string $url
+	 *
+	 * @return string|WP_Error
+	 */
+	protected static function extract_content_from_url( $url ) {
+		$url = esc_url_raw( $url );
+
+		$filename_length = strlen( self::REQUIRED_FILENAME );
+		if ( strtolower( substr( $url, - $filename_length ) ) !== self::REQUIRED_FILENAME ) {
+			return new WP_Error(
+				'resource_url_invalid',
+				sprintf(
+					/* translators: %s: file name */
+					__( 'URL must end in %s!', 'wporg-plugins' ),
+					'<code>' . self::REQUIRED_FILENAME . '</code>'
+				)
+			);
+		}
+
+		$response      = wp_safe_remote_get( $url );
+		$response_code = wp_remote_retrieve_response_code( $response );
+
+		if ( is_wp_error( $response ) ) {
+			return $response;
+		} elseif ( 200 !== $response_code ) {
+			return new WP_Error(
+				'resource_url_unexpected_response',
+				__( 'URL returned an unexpected status code.', 'wporg-plugins' ),
+				array(
+					'status' => $response_code,
+				)
+			);
+		}
+
+		return wp_remote_retrieve_body( $response );
+	}
+
+	/**
+	 * Get the contents of a block.json file via a path in the filesystem.
+	 *
+	 * @param string $file
+	 *
+	 * @return string|WP_Error
+	 */
+	protected static function extract_content_from_file( $file ) {
+		$filename_length = strlen( self::REQUIRED_FILENAME );
+		if ( strtolower( substr( $file, - $filename_length ) ) !== self::REQUIRED_FILENAME ) {
+			return new WP_Error(
+				'resource_file_invalid',
+				sprintf(
+					/* translators: %s: file name */
+					__( 'File must be named %s!', 'wporg-plugins' ),
+					'<code>' . self::REQUIRED_FILENAME . '</code>'
+				)
+			);
+		}
+
+		if ( ! is_readable( $file ) ) {
+			return new WP_Error(
+				'resource_file_unreadable',
+				__( 'The file could not be read.', 'wporg-plugins' ),
+				array(
+					'file' => $file,
+				)
+			);
+		}
+
+		$content = file_get_contents( $file );
+
+		if ( false === $content ) {
+			return new WP_Error(
+				'resource_file_failed_retrieval',
+				__( 'Could not get the contents of the file.', 'wporg-plugins' ),
+				array(
+					'file' => $file,
+				)
+			);
+		}
+
+		return $content;
+	}
+
+	/**
+	 * Parse a JSON string into an object, and handle parsing errors.
+	 *
+	 * @param string $content
+	 *
+	 * @return object|WP_Error
+	 */
+	protected static function parse_content( $content ) {
+		$parsed = json_decode( $content );
+		$error  = json_last_error_msg();
+
+		// TODO Once we are on PHP 7.3 we can use the JSON_THROW_ON_ERROR option and catch an exception here.
+		if ( 'No error' !== $error ) {
+			return new WP_Error(
+				'json_parse_error',
+				sprintf(
+					__( 'JSON Parser: %s', 'wporg-plugins' ),
+					esc_html( $error )
+				),
+				array(
+					'error_code' => json_last_error(),
+				)
+			);
+		}
+
+		return $parsed;
+	}
+}