diff --git a/src/wp-includes/link-template.php b/src/wp-includes/link-template.php
index 6ad7f058b9..0d06a3f9ca 100644
--- a/src/wp-includes/link-template.php
+++ b/src/wp-includes/link-template.php
@@ -3538,36 +3538,81 @@ function get_edit_profile_url( $user_id = 0, $scheme = 'admin' ) {
return apply_filters( 'edit_profile_url', $url, $user_id, $scheme);
}
+/**
+ * Returns the canonical URL for a post.
+ *
+ * When the post is the same as the current requested page the function will handle the
+ * pagination arguments too.
+ *
+ * @since 4.6.0
+ *
+ * @param int|WP_Post $post Optional. Post ID or object. Default is global `$post`.
+ * @return string|false The canonical URL, or false if the post does not exist or has not
+ * been published yet.
+ */
+function wp_get_canonical_url( $post = null ) {
+ $post = get_post( $post );
+
+ if ( ! $post ) {
+ return false;
+ }
+
+ if ( 'publish' !== $post->post_status ) {
+ return false;
+ }
+
+ $canonical_url = get_permalink( $post );
+
+ // If a canonical is being generated for the current page, make sure it has pagination if needed.
+ if ( $post->ID === get_queried_object_id() ) {
+ $page = get_query_var( 'page', 0 );
+ if ( $page >= 2 ) {
+ if ( '' == get_option( 'permalink_structure' ) ) {
+ $canonical_url = add_query_arg( 'page', $page, $canonical_url );
+ } else {
+ $canonical_url = trailingslashit( $canonical_url ) . user_trailingslashit( $page, 'single_paged' );
+ }
+ }
+
+ $cpage = get_query_var( 'cpage', 0 );
+ if ( $cpage ) {
+ $canonical_url = get_comments_pagenum_link( $cpage );
+ }
+ }
+
+ /**
+ * Filters the canonical URL for a post.
+ *
+ * @since 4.6.0
+ *
+ * @param string $string The post's canonical URL.
+ * @param WP_Post $post Post object.
+ */
+ return apply_filters( 'get_canonical_url', $canonical_url, $post );
+}
+
/**
* Outputs rel=canonical for singular queries.
*
* @since 2.9.0
+ * @since 4.6.0 Adjusted to use `wp_get_canonical_url()`.
*/
function rel_canonical() {
if ( ! is_singular() ) {
return;
}
- if ( ! $id = get_queried_object_id() ) {
+ $id = get_queried_object_id();
+
+ if ( 0 === $id ) {
return;
}
- $url = get_permalink( $id );
+ $url = wp_get_canonical_url( $id );
- $page = get_query_var( 'page' );
- if ( $page >= 2 ) {
- if ( '' == get_option( 'permalink_structure' ) ) {
- $url = add_query_arg( 'page', $page, $url );
- } else {
- $url = trailingslashit( $url ) . user_trailingslashit( $page, 'single_paged' );
- }
+ if ( ! empty( $url ) ) {
+ echo '' . "\n";
}
-
- $cpage = get_query_var( 'cpage' );
- if ( $cpage ) {
- $url = get_comments_pagenum_link( $cpage );
- }
- echo '\n";
}
/**
diff --git a/tests/phpunit/tests/link/wpGetCanonicalURL.php b/tests/phpunit/tests/link/wpGetCanonicalURL.php
new file mode 100644
index 0000000000..dbbd630008
--- /dev/null
+++ b/tests/phpunit/tests/link/wpGetCanonicalURL.php
@@ -0,0 +1,143 @@
+post->create( array(
+ 'post_status' => 'publish',
+ ) );
+ }
+
+ public static function wpTearDownAfterClass() {
+ wp_delete_post( self::$post_id, true );
+ }
+
+ /**
+ * Test for a non existing post.
+ */
+ public function test_non_existing_post() {
+ $this->assertFalse( wp_get_canonical_url( -1 ) );
+ }
+
+ /**
+ * Test for a post that is not published.
+ */
+ public function test_post_status() {
+ $post_id = self::factory()->post->create( array(
+ 'post_status' => 'draft',
+ ) );
+
+ $this->assertFalse( wp_get_canonical_url( $post_id ) );
+ }
+
+ /**
+ * Test for a page that is not the queried object.
+ */
+ public function test_non_current_page() {
+ $this->assertEquals( get_permalink( self::$post_id ), wp_get_canonical_url( self::$post_id ) );
+ }
+
+ /**
+ * Test non permalink structure page usage.
+ */
+ public function test_paged_with_plain_permalink_structure() {
+ $link = add_query_arg( array(
+ 'page' => 2,
+ 'foo' => 'bar',
+ ), get_permalink( self::$post_id ) );
+
+ $this->go_to( $link );
+
+ $expected = add_query_arg( array(
+ 'page' => 2,
+ ), get_permalink( self::$post_id ) );
+
+ $this->assertEquals( $expected, wp_get_canonical_url( self::$post_id ) );
+ }
+
+ /**
+ * Test permalink structure page usage.
+ */
+ public function test_paged_with_custom_permalink_structure() {
+ $this->set_permalink_structure( '/%postname%/' );
+ $page = 2;
+
+ $link = add_query_arg( array(
+ 'page' => $page,
+ 'foo' => 'bar',
+ ), get_permalink( self::$post_id ) );
+
+ $this->go_to( $link );
+
+ $expected = trailingslashit( get_permalink( self::$post_id ) ) . user_trailingslashit( $page, 'single_paged' );
+
+ $this->assertEquals( $expected, wp_get_canonical_url( self::$post_id ) );
+ }
+
+ /**
+ * Test non permalink structure comment page usage.
+ */
+ public function test_comments_paged_with_plain_permalink_structure() {
+ $cpage = 2;
+
+ $link = add_query_arg( array(
+ 'cpage' => $cpage,
+ 'foo' => 'bar',
+ ), get_permalink( self::$post_id ) );
+
+ $this->go_to( $link );
+
+ $expected = add_query_arg( array(
+ 'cpage' => $cpage,
+ ), get_permalink( self::$post_id ) . '#comments' );
+
+ $this->assertEquals( $expected , wp_get_canonical_url( self::$post_id ) );
+ }
+
+ /**
+ * Test permalink structure comment page usage.
+ */
+ public function test_comments_paged_with_pretty_permalink_structure() {
+ global $wp_rewrite;
+
+ $this->set_permalink_structure( '/%postname%/' );
+ $cpage = 2;
+
+ $link = add_query_arg( array(
+ 'cpage' => $cpage,
+ 'foo' => 'bar',
+ ), get_permalink( self::$post_id ) );
+
+ $this->go_to( $link );
+
+ $expected = user_trailingslashit( trailingslashit( get_permalink( self::$post_id ) ) . $wp_rewrite->comments_pagination_base . '-' . $cpage, 'commentpaged' ) . '#comments';
+
+ $this->assertEquals( $expected , wp_get_canonical_url( self::$post_id ) );
+ }
+
+ /**
+ * Test calling of filter.
+ */
+ public function test_get_canonical_url_filter() {
+ add_filter( 'get_canonical_url', array( $this, 'canonical_url_filter' ) );
+ $canonical_url = wp_get_canonical_url( self::$post_id );
+ remove_filter( 'get_canonical_url', array( $this, 'canonical_url_filter' ) );
+
+ $this->assertEquals( $this->canonical_url_filter(), $canonical_url );
+ }
+
+ /**
+ * Filter callback for testing of filter usage.
+ *
+ * @return string
+ */
+ public function canonical_url_filter() {
+ return 'http://canonical.example.org/';
+ }
+}