Integrate with Yoast SEO llms.txt to use .md URLs

src/Integration/YoastLlmsTxt.php

@@ -0,0 +1,145 @@
+<?php
+/**
+ * Yoast SEO llms.txt integration.
+ *
+ * Rewrites URLs in Yoast's llms.txt to point to .md versions
+ * for post types supported by Markdown Alternate.
+ *
+ * @package MarkdownAlternate
+ */
+
+namespace MarkdownAlternate\Integration;
+
+use MarkdownAlternate\PostTypeSupport;
+
+/**
+ * Filters post URLs to .md during Yoast SEO's llms.txt generation.
+ *
+ * Wraps Yoast's generation triggers with permalink filters so URLs
+ * are rewritten inline — no file post-processing needed.
+ */
+class YoastLlmsTxt {
+
+    /**
+     * Whether we're currently inside llms.txt generation.
+     *
+     * @var bool
+     */
+    private bool $generating = false;
+
+    /**
+     * Register hooks to wrap Yoast's llms.txt generation.
+     *
+     * @return void
+     */
+    public function register(): void {
+        // Wrap each trigger that causes Yoast to (re)generate the llms.txt file.
+        // Priority 9 = before Yoast's priority 10, priority 11 = after.
+
+        // 1. Feature toggle (enable/disable llms.txt in Yoast settings).
+        add_action( 'update_option_wpseo', [ $this, 'start' ], 9 );
+        add_action( 'update_option_wpseo', [ $this, 'stop' ], 11 );
+
+        // 2. llms.txt page selection settings change.
+        add_action( 'update_option_wpseo_llmstxt', [ $this, 'start' ], 9 );
+        add_action( 'update_option_wpseo_llmstxt', [ $this, 'stop' ], 11 );
+
+        // 3. Weekly cron regeneration.
+        add_action( 'wpseo_llms_txt_population', [ $this, 'start' ], 9 );
+        add_action( 'wpseo_llms_txt_population', [ $this, 'stop' ], 11 );
+    }
+
+    /**
+     * Enable URL rewriting before Yoast generates the file.
+     *
+     * @return void
+     */
+    public function start(): void {
+        if ( $this->generating ) {
+            return;
+        }
+        $this->generating = true;
+
+        // from_meta() path: $meta->canonical goes through this filter.
+        add_filter( 'wpseo_canonical', [ $this, 'rewrite_canonical' ], 10, 2 );
+
+        // from_post() fallback path: uses get_permalink() directly.
+        add_filter( 'post_link', [ $this, 'rewrite_post_link' ], 10, 2 );
+        add_filter( 'page_link', [ $this, 'rewrite_page_link' ], 10, 2 );
+        add_filter( 'post_type_link', [ $this, 'rewrite_post_link' ], 10, 2 );
+    }
+
+    /**
+     * Disable URL rewriting after Yoast finishes generating.
+     *
+     * @return void
+     */
+    public function stop(): void {
+        if ( ! $this->generating ) {
+            return;
+        }
+        $this->generating = false;
+
+        remove_filter( 'wpseo_canonical', [ $this, 'rewrite_canonical' ], 10 );
+        remove_filter( 'post_link', [ $this, 'rewrite_post_link' ], 10 );
+        remove_filter( 'page_link', [ $this, 'rewrite_page_link' ], 10 );
+        remove_filter( 'post_type_link', [ $this, 'rewrite_post_link' ], 10 );
+    }
+
+    /**
+     * Rewrite Yoast canonical URL to .md for supported post types.
+     *
+     * @param string                                              $canonical    The canonical URL.
+     * @param \Yoast\WP\SEO\Presentations\Indexable_Presentation $presentation The Yoast indexable presentation.
+     * @return string
+     */
+    public function rewrite_canonical( $canonical, $presentation ) {
+        if ( empty( $canonical ) || ! is_object( $presentation ) || ! isset( $presentation->model ) ) {
+            return $canonical;
+        }
+
+        if ( $presentation->model->object_type !== 'post' ) {
+            return $canonical;
+        }
+
+        if ( ! PostTypeSupport::is_supported( $presentation->model->object_sub_type ) ) {
+            return $canonical;
+        }
+
+        return rtrim( $canonical, '/' ) . '.md';
+    }
+
+    /**
+     * Rewrite post/CPT permalink to .md.
+     *
+     * Works for both post_link and post_type_link filters.
+     *
+     * @param string   $url  The permalink.
+     * @param \WP_Post $post The post object.
+     * @return string
+     */
+    public function rewrite_post_link( $url, $post ): string {
+        $post_type = get_post_type( $post );
+        if ( ! $post_type || ! PostTypeSupport::is_supported( $post_type ) ) {
+            return $url;
+        }
+
+        return rtrim( $url, '/' ) . '.md';
+    }
+
+    /**
+     * Rewrite page permalink to .md.
+     *
+     * @param string $url     The page URL.
+     * @param int    $post_id The page ID.
+     * @return string
+     */
+    public function rewrite_page_link( $url, $post_id ): string {
+        $post_type = get_post_type( $post_id );
+        if ( ! $post_type || ! PostTypeSupport::is_supported( $post_type ) ) {
+            return $url;
+        }
+
+        return rtrim( $url, '/' ) . '.md';
+    }
+}

src/Plugin.php

@@ -8,6 +8,7 @@
 namespace MarkdownAlternate;
 
 use MarkdownAlternate\Discovery\AlternateLinkHandler;
+use MarkdownAlternate\Integration\YoastLlmsTxt;
 use MarkdownAlternate\Router\RewriteHandler;
 use YahnisElsts\PluginUpdateChecker\v5\PucFactory;
 
@@ -64,6 +65,19 @@ private function __construct() {
             MARKDOWN_ALTERNATE_FILE,
             'markdown-alternate'
         );
+
+        add_action( 'plugins_loaded', [ $this, 'register_integrations' ] );
+    }
+
+    /**
+     * Register integrations with third-party plugins.
+     *
+     * @return void
+     */
+    public function register_integrations(): void {
+        if ( defined( 'WPSEO_VERSION' ) ) {
+            ( new YoastLlmsTxt() )->register();
+        }
     }
 
     /**