Synthesize template parts only from separable chrome

includes/class-static-site-importer-document.php

@@ -228,12 +228,12 @@ private function compute_selection(): array {
 		$body = $this->first_element( 'body' );
 		$root = $body instanceof DOMElement ? $body : $this->dom->documentElement;
 
-		$footer             = $this->first_element( 'footer' );
 		$main               = $this->first_element( 'main' );
+		$footer             = $this->first_separable_landmark( 'footer', $main );
 		$effective_children = $this->effective_root_children( $root, $main );
 
 		$header       = $this->first_plausible_global_header( $effective_children );
-		$nav          = $this->first_plausible_global_nav( $effective_children, $header );
+		$nav          = $this->first_plausible_global_nav( $effective_children, $header, $main );
 		$body_headers = $this->body_content_headers( $effective_children, $header, $nav );
 
 		if ( $header instanceof DOMElement && $this->contains_same_node( $body_headers, $header ) ) {
@@ -425,12 +425,21 @@ private function first_plausible_global_header( array $effective_children ): ?DO
 	/**
 	 * Find a nav that is plausible reusable site chrome.
 	 *
+	 * Navs embedded inside the page body (`<main>`) are page content, not
+	 * separable global chrome: extracting them duplicates the markup because the
+	 * body keeps its own copy.
+	 *
 	 * @param DOMElement[]    $effective_children Effective body-level direct children.
 	 * @param DOMElement|null $header             Selected header element.
+	 * @param DOMElement|null $main               Main landmark element if present.
 	 * @return DOMElement|null
 	 */
-	private function first_plausible_global_nav( array $effective_children, ?DOMElement $header ): ?DOMElement {
+	private function first_plausible_global_nav( array $effective_children, ?DOMElement $header, ?DOMElement $main = null ): ?DOMElement {
 		foreach ( $this->dom->getElementsByTagName( 'nav' ) as $nav ) {
+			if ( $main instanceof DOMElement && $this->is_descendant_of( $nav, $main ) ) {
+				continue;
+			}
+
 			if ( $header instanceof DOMElement && $this->is_descendant_of( $nav, $header ) ) {
 				return $nav;
 			}
@@ -443,6 +452,32 @@ private function first_plausible_global_nav( array $effective_children, ?DOMElem
 		return null;
 	}
 
+	/**
+	 * Find the first landmark that is separable from the page body.
+	 *
+	 * Landmarks nested inside `<main>` stay in the page body fragment, so
+	 * extracting them as shared chrome would duplicate their markup.
+	 *
+	 * @param string          $tag  Landmark tag name.
+	 * @param DOMElement|null $main Main landmark element if present.
+	 * @return DOMElement|null
+	 */
+	private function first_separable_landmark( string $tag, ?DOMElement $main ): ?DOMElement {
+		foreach ( $this->dom->getElementsByTagName( $tag ) as $node ) {
+			if ( ! $node instanceof DOMElement ) {
+				continue;
+			}
+
+			if ( $main instanceof DOMElement && $this->is_descendant_of( $node, $main ) ) {
+				continue;
+			}
+
+			return $node;
+		}
+
+		return null;
+	}
+
 	/**
 	 * Check whether a header looks like global site chrome rather than section content.
 	 *

includes/class-static-site-importer-theme-materializer.php

@@ -991,6 +991,7 @@ public static function template_part_artifact_writes( string $theme_dir, array $
 	 */
 	private static function source_file_template_parts( array $artifacts ): array {
 		$files = isset( $artifacts['source_files'] ) && is_array( $artifacts['source_files'] ) ? $artifacts['source_files'] : array();
+		$files = self::entrypoint_first_source_files( $files, $artifacts );
 		foreach ( $files as $file ) {
 			if ( ! is_array( $file ) || ! isset( $file['path'] ) || ! is_scalar( $file['path'] ) ) {
 				continue;
@@ -1024,6 +1025,43 @@ private static function source_file_template_parts( array $artifacts ): array {
 		return array();
 	}
 
+	/**
+	 * Order source files so the site entrypoint is scanned first.
+	 *
+	 * The entrypoint page is the imported front page, so its chrome is the
+	 * authoritative candidate for shared template parts. Without this ordering
+	 * the fallback synthesizes parts from whichever file happens to sort first.
+	 *
+	 * @param array<int,mixed>    $files     Source files.
+	 * @param array<string,mixed> $artifacts WordPress artifacts from Blocks Engine.
+	 * @return array<int,mixed>
+	 */
+	private static function entrypoint_first_source_files( array $files, array $artifacts ): array {
+		$entrypoint = '';
+		foreach ( array( 'entry_path', 'entrypoint' ) as $key ) {
+			if ( isset( $artifacts[ $key ] ) && is_scalar( $artifacts[ $key ] ) && '' !== trim( (string) $artifacts[ $key ] ) ) {
+				$entrypoint = ltrim( str_replace( '\\', '/', trim( (string) $artifacts[ $key ] ) ), '/' );
+				break;
+			}
+		}
+		if ( '' === $entrypoint ) {
+			return $files;
+		}
+
+		$leading  = array();
+		$trailing = array();
+		foreach ( $files as $file ) {
+			$path = is_array( $file ) && isset( $file['path'] ) && is_scalar( $file['path'] ) ? ltrim( str_replace( '\\', '/', (string) $file['path'] ), '/' ) : '';
+			if ( '' !== $path && ( $path === $entrypoint || str_ends_with( $path, '/' . $entrypoint ) ) ) {
+				$leading[] = $file;
+				continue;
+			}
+			$trailing[] = $file;
+		}
+
+		return array_merge( $leading, $trailing );
+	}
+
 	/**
 	 * Convert source HTML landmarks into reusable block theme parts.
 	 *
@@ -1079,7 +1117,11 @@ private static function strip_inline_svg_markup( string $html ): string {
 	}
 
 	/**
-	 * Return the first matching landmark's outer HTML.
+	 * Return the first separable landmark's outer HTML.
+	 *
+	 * Landmarks nested inside `<main>` remain part of the page body markup, so
+	 * synthesizing a shared template part from them would render the same chrome
+	 * twice. Only landmarks outside the page body are reusable site chrome.
 	 *
 	 * @param string $html Source HTML document.
 	 * @param string $tag  Landmark tag name.
@@ -1099,9 +1141,42 @@ private static function first_landmark_html( string $html, string $tag ): string
 			return '';
 		}
 
-		$nodes = $dom->getElementsByTagName( $tag );
-		$node  = $nodes->length > 0 ? $nodes->item( 0 ) : null;
-		return $node instanceof DOMElement ? trim( (string) $dom->saveHTML( $node ) ) : '';
+		$mains = $dom->getElementsByTagName( 'main' );
+		$main  = $mains->length > 0 ? $mains->item( 0 ) : null;
+
+		foreach ( $dom->getElementsByTagName( $tag ) as $node ) {
+			if ( ! $node instanceof DOMElement ) {
+				continue;
+			}
+
+			if ( $main instanceof DOMElement && self::dom_is_descendant_of( $node, $main ) ) {
+				continue;
+			}
+
+			return trim( (string) $dom->saveHTML( $node ) );
+		}
+
+		return '';
+	}
+
+	/**
+	 * Check whether a DOM node is contained by another element.
+	 *
+	 * @param DOMElement $candidate Candidate element.
+	 * @param DOMElement $ancestor  Ancestor element.
+	 * @return bool
+	 */
+	private static function dom_is_descendant_of( DOMElement $candidate, DOMElement $ancestor ): bool {
+		$node = $candidate->parentNode;
+		while ( $node instanceof DOMNode ) {
+			if ( $node->isSameNode( $ancestor ) ) {
+				return true;
+			}
+
+			$node = $node->parentNode;
+		}
+
+		return false;
 	}
 
 	/**

includes/class-static-site-importer-transformer-adapter.php

@@ -95,6 +95,7 @@ private function compiled_result_from_transformer_contract( array $result, array
 		$artifacts['documents']         = ! empty( $view['documents'] ) && is_array( $view['documents'] ) ? $view['documents'] : ( isset( $result['documents'] ) && is_array( $result['documents'] ) ? $result['documents'] : array() );
 		$artifacts['files']             = $this->artifact_files_from_site_report( $materialization_plan, ! empty( $view ) ? $view : $result );
 		$artifacts['source_files']      = $this->source_files_from_artifact( $artifact );
+		$artifacts['entry_path']        = $this->entry_path_from_artifact( $artifact );
 		$artifacts['site']              = $materialization_plan;
 		$artifacts['compiled_site']     = ! empty( $view['compiled_site'] ) && is_array( $view['compiled_site'] ) ? $view['compiled_site'] : array();
 		$artifacts['template_parts']    = isset( $materialization_plan['template_parts'] ) && is_array( $materialization_plan['template_parts'] ) ? $materialization_plan['template_parts'] : array();
@@ -116,6 +117,22 @@ private function compiled_result_from_transformer_contract( array $result, array
 		return $compiled;
 	}
 
+	/**
+	 * Read the declared website entrypoint from an artifact bundle.
+	 *
+	 * @param array<string,mixed> $artifact Website artifact bundle.
+	 * @return string
+	 */
+	private function entry_path_from_artifact( array $artifact ): string {
+		foreach ( array( 'entry_path', 'entrypoint' ) as $key ) {
+			if ( isset( $artifact[ $key ] ) && is_scalar( $artifact[ $key ] ) && '' !== trim( (string) $artifact[ $key ] ) ) {
+				return ltrim( str_replace( '\\', '/', trim( (string) $artifact[ $key ] ) ), '/' );
+			}
+		}
+
+		return '';
+	}
+
 	/**
 	 * Preserve safe source artifact files for downstream WordPress materializers.
 	 *