Block Library: Add a Post Tags block. (#19580)

* Block Library: Add a Post Tags block.

* Block Library: Fix issue with Post Tags block when there are no tags.

* Fixtures & Linting

lib/blocks.php

@@ -40,6 +40,7 @@ function gutenberg_reregister_core_block_types() {
 		'post-date.php'           => 'core/post-date',
 		'post-excerpt.php'        => 'core/post-excerpt',
 		'post-featured-image.php' => 'core/post-featured-image',
+		'post-tags.php'           => 'core/post-tags',
 	);
 
 	$registry = WP_Block_Type_Registry::get_instance();

packages/block-library/src/index.js

@@ -73,6 +73,7 @@ import * as postCommentsForm from './post-comments-form';
 import * as postDate from './post-date';
 import * as postExcerpt from './post-excerpt';
 import * as postFeaturedImage from './post-featured-image';
+import * as postTags from './post-tags';
 
 /**
  * Function to register an individual block.
@@ -203,6 +204,7 @@ export const __experimentalRegisterExperimentalCoreBlocks =
 								postDate,
 								postExcerpt,
 								postFeaturedImage,
+								postTags,
 						  ]
 						: [] ),
 				].forEach( registerBlock );

packages/block-library/src/post-tags/block.json

@@ -0,0 +1,4 @@
+{
+	"name": "core/post-tags",
+	"category": "layout"
+}

packages/block-library/src/post-tags/edit.js

@@ -0,0 +1,42 @@
+/**
+ * WordPress dependencies
+ */
+import { useEntityProp, useEntityId } from '@wordpress/core-data';
+import { useSelect } from '@wordpress/data';
+import { __ } from '@wordpress/i18n';
+
+function PostTagsDisplay() {
+	const [ tags ] = useEntityProp( 'postType', 'post', 'tags' );
+	const tagLinks = useSelect(
+		( select ) => {
+			const { getEntityRecord } = select( 'core' );
+			let loaded = true;
+			const links = tags.map( ( tagId ) => {
+				const tag = getEntityRecord( 'taxonomy', 'post_tag', tagId );
+				if ( ! tag ) {
+					return ( loaded = false );
+				}
+				return (
+					<a key={ tagId } href={ tag.link }>
+						{ tag.name }
+					</a>
+				);
+			} );
+			return loaded && links;
+		},
+		[ tags ]
+	);
+	return (
+		tagLinks &&
+		( tagLinks.length === 0
+			? __( 'No tags.' )
+			: tagLinks.reduce( ( prev, curr ) => [ prev, ' | ', curr ] ) )
+	);
+}
+
+export default function PostTagsEdit() {
+	if ( ! useEntityId( 'postType', 'post' ) ) {
+		return 'Post Tags Placeholder';
+	}
+	return <PostTagsDisplay />;
+}

packages/block-library/src/post-tags/index.js

@@ -0,0 +1,18 @@
+/**
+ * WordPress dependencies
+ */
+import { __ } from '@wordpress/i18n';
+
+/**
+ * Internal dependencies
+ */
+import metadata from './block.json';
+import edit from './edit';
+
+const { name } = metadata;
+export { metadata, name };
+
+export const settings = {
+	title: __( 'Post Tags' ),
+	edit,
+};

packages/block-library/src/post-tags/index.php

@@ -0,0 +1,39 @@
+<?php
+/**
+ * Server-side rendering of the `core/post-tags` block.
+ *
+ * @package WordPress
+ */
+
+/**
+ * Renders the `core/post-tags` block on the server.
+ *
+ * @return string Returns the filtered post tags for the current post wrapped inside "a" tags.
+ */
+function render_block_core_post_tags() {
+	$post = gutenberg_get_post_from_context();
+	if ( ! $post ) {
+		return '';
+	}
+	$post_tags = get_the_tags();
+	if ( ! empty( $post_tags ) ) {
+		$output = '';
+		foreach ( $post_tags as $tag ) {
+			$output .= '<a href="' . get_tag_link( $tag->term_id ) . '">' . $tag->name . '</a>' . ' | ';
+		}
+		return trim( $output, ' | ' );
+	}
+}
+
+/**
+ * Registers the `core/post-tags` block on the server.
+ */
+function register_block_core_post_tags() {
+	register_block_type(
+		'core/post-tags',
+		array(
+			'render_callback' => 'render_block_core_post_tags',
+		)
+	);
+}
+add_action( 'init', 'register_block_core_post_tags' );

packages/e2e-tests/fixtures/blocks/core__post-tags.html

@@ -0,0 +1 @@
+<!-- wp:post-tags /-->

packages/e2e-tests/fixtures/blocks/core__post-tags.json

@@ -0,0 +1,10 @@
+[
+    {
+        "clientId": "_clientId_0",
+        "name": "core/post-tags",
+        "isValid": true,
+        "attributes": {},
+        "innerBlocks": [],
+        "originalContent": ""
+    }
+]

packages/e2e-tests/fixtures/blocks/core__post-tags.parsed.json

@@ -0,0 +1,18 @@
+[
+    {
+        "blockName": "core/post-tags",
+        "attrs": {},
+        "innerBlocks": [],
+        "innerHTML": "",
+        "innerContent": []
+    },
+    {
+        "blockName": null,
+        "attrs": {},
+        "innerBlocks": [],
+        "innerHTML": "\n",
+        "innerContent": [
+            "\n"
+        ]
+    }
+]

packages/e2e-tests/fixtures/blocks/core__post-tags.serialized.html

@@ -0,0 +1 @@
+<!-- wp:post-tags /-->