SSR: Add wp-show attribute directive processor

phpunit/directives/attributes/wp-show.php

@@ -0,0 +1,64 @@
+<?php
+/**
+ * wp-show tag directive test.
+ */
+
+ require_once __DIR__ . '/../../../src/directives/attributes/wp-show.php';
+
+ require_once __DIR__ . '/../../../src/directives/class-wp-directive-context.php';
+ require_once __DIR__ . '/../../../src/directives/class-wp-directive-processor.php';
+
+ require_once __DIR__ . '/../../../src/directives/wp-html.php';
+
+/**
+ * Tests for the wp-show tag directive.
+ *
+ * @group  directives
+ * @covers process_wp_show
+ */
+class Tests_Directives_WpShow extends WP_UnitTestCase {
+	public function test_directive_leaves_content_unchanged_if_when_is_true() {
+		$markup = <<<EOF
+			<div wp-show="context.myblock.open">
+				I should be shown!
+			</div>
+EOF;
+		$tags = new WP_Directive_Processor( $markup );
+		$tags->next_tag();
+
+		$context_before = new WP_Directive_Context( array( 'myblock' => array( 'open' => true ) ) );
+		$context        = clone $context_before;
+		process_wp_show( $tags, $context );
+
+		$tags->next_tag( array( 'tag_closers' => 'visit' ) );
+		process_wp_show( $tags, $context );
+
+		$this->assertSame( $markup, $tags->get_updated_html() );
+		$this->assertSame( $context_before->get_context(), $context->get_context(), 'wp-show directive changed context' );
+	}
+
+	public function test_directive_wraps_content_in_template_if_when_is_false() {
+		$markup = <<<EOF
+			<div wp-show="context.myblock.open">
+				I should be shown!
+			</div>
+EOF;
+		$tags = new WP_Directive_Processor( $markup );
+		$tags->next_tag();
+
+		$context_before = new WP_Directive_Context( array( 'myblock' => array( 'open' => false ) ) );
+		$context        = clone $context_before;
+		process_wp_show( $tags, $context );
+
+		$tags->next_tag( array( 'tag_closers' => 'visit' ) );
+		process_wp_show( $tags, $context );
+
+		$updated_markup = <<<EOF
+			<div wp-show="context.myblock.open"><template>
+				I should be shown!
+			</template></div>
+EOF;
+		$this->assertSame( $updated_markup, $tags->get_updated_html() );
+		$this->assertSame( $context_before->get_context(), $context->get_context(), 'wp-show directive changed context' );
+	}
+}

src/directives/attributes/wp-show.php

@@ -0,0 +1,27 @@
+<?php
+
+require_once __DIR__ . '/../utils.php';
+
+function process_wp_show( $tags, $context ) {
+	if ( ! $tags->is_tag_closer() ) { // TODO: Exclude void and self-closing!
+		set_bookmark_for_directive( $tags, 'wp-show' );
+		return;
+	}
+
+	$end = 'wp-show-closer';
+	$tags->set_bookmark( 'wp-show-closer' );
+	$start = seek_bookmark_for_directive( $tags, 'wp-show' );
+
+	$value = $tags->get_attribute( 'wp-show' );
+	if ( null !== $value ) {
+		$show = evaluate( $value, $context->get_context() );
+
+		if ( ! $show ) {
+			$content = $tags->get_content_inside_bookmarks( $start, $end );
+			$tags->set_content_inside_bookmarks( $start, $end, '<template>' . $content . '</template>' );
+		}
+	}
+	$tags->seek( $end );
+	$tags->release_bookmark( $start );
+	$tags->release_bookmark( $end );
+}

src/directives/class-wp-directive-processor.php

@@ -0,0 +1,37 @@
+<?php
+
+require_once __DIR__ . '/wp-html.php';
+
+class WP_Directive_Processor extends WP_HTML_Tag_Processor {
+	public function get_content_inside_bookmarks( $start_bookmark, $end_bookmark ) {
+		if ( ! isset( $this->bookmarks[ $start_bookmark ], $this->bookmarks[ $end_bookmark ] ) ) {
+			return null;
+		}
+
+		$start = $this->bookmarks[ $start_bookmark ];
+		$end   = $this->bookmarks[ $end_bookmark ];
+
+		return substr( $this->get_updated_html(), $start->end + 1, $end->start - $start->end - 2 );
+	}
+
+	public function set_content_inside_bookmarks( $start_bookmark, $end_bookmark, $content ) {
+		if ( ! isset( $this->bookmarks[ $start_bookmark ], $this->bookmarks[ $end_bookmark ] ) ) {
+			return null;
+		}
+
+		$start = $this->bookmarks[ $start_bookmark ];
+		$end   = $this->bookmarks[ $end_bookmark ];
+
+        $this->lexical_updates[] = new WP_HTML_Text_Replacement( $start->end + 1, $end->start - 1, $content );
+	}
+
+	/**
+	 * Checks whether a bookmark with the given name exists.
+	 *
+	 * @param string $bookmark_name Name to identify a bookmark that potentially exists.
+	 * @return bool Whether that bookmark exists.
+	 */
+	public function has_bookmark( $bookmark_name ) {
+		return array_key_exists( $bookmark_name, $this->bookmarks );
+	}
+}

src/directives/utils.php

@@ -49,3 +49,25 @@ function set_style( $style, $name, $value ) {
 	}
 	return implode( ';', $style_assignments );
 }
+
+function count_bookmarks_for_directive( $tags, $directive ) {
+	$i = 0;
+	while ( $tags->has_bookmark( $directive . '-' . $i ) ) {
+		++$i;
+	}
+	return $i;
+}
+
+function set_bookmark_for_directive( $tags, $directive ) {
+	$i        = count_bookmarks_for_directive( $tags, $directive );
+	$bookmark = $directive . '-' . $i;
+	$tags->set_bookmark( $bookmark );
+	return $bookmark;
+}
+
+function seek_bookmark_for_directive( $tags, $directive ) {
+	$i        = count_bookmarks_for_directive( $tags, $directive ) - 1;
+	$bookmark = $directive . '-' . $i;
+	$tags->seek( $bookmark );
+	return $bookmark;
+}

wp-directives.php

@@ -43,6 +43,7 @@ function () {
 
 require_once __DIR__ . '/src/directives/attributes/wp-bind.php';
 require_once __DIR__ . '/src/directives/attributes/wp-class.php';
+require_once __DIR__ . '/src/directives/attributes/wp-show.php';
 require_once __DIR__ . '/src/directives/attributes/wp-style.php';
 require_once __DIR__ . '/src/directives/tags/wp-context.php';
 
@@ -216,6 +217,7 @@ function process_directives_in_block( $block_content ) {
 		'wp-context' => 'process_wp_context',
 		'wp-bind'    => 'process_wp_bind',
 		'wp-class'   => 'process_wp_class',
+		'wp-show'    => 'process_wp_show',
 		'wp-style'   => 'process_wp_style',
 	);