Fix broken latest posts page links (#581)

* fix(MslsBlog): add is_home() for posts pages

When a static page is set as WordPress "Posts page",
is_home() returns true but is_front_page() returns
false. The language switcher now detects this case
and falls back to the target blog's page_for_posts
when pages are not explicitly linked via MSLS.

Closes #97

* fix(MslsOptions): prevent blog slug corruption

The greedy str_replace in check_for_blog_slug()
matched /blog as substring of /blogg/, producing
truncated URLs like /sv/g/ instead of /sv/blogg/.
Replace with boundary-aware prefix stripping that
only removes the slug when followed by / or EOL.

* refactor(MslsBlog): rename $is_home to $is_front_page

Rename misleading variable and apply permalink hook
to the posts-page fallback for consistent filtering.

* fix(MslsOptions): only re-add slug when stripped

The is_main_site re-addition of the blog slug was
unconditional, corrupting URLs where the slug was
not stripped (e.g. /blogg/ becoming /blog/blogg/).

* test(MslsBlog): drop explicit apply_filters mock

Brain\Monkey handles apply_filters by default. The
explicit mock was inconsistent with other tests and
unnecessarily fragile.

---------

Co-authored-by: Dennis Ploetner <re@lloc.de>

Author: apermo

includes/MslsBlog.php

@@ -134,12 +134,18 @@ public function get_url( $options ) {
 	protected function get_permalink( OptionsInterface $options ) {
 		$url = null;
 
-		$is_home = is_front_page();
+		$is_front_page = is_front_page();
+		$is_posts_page = ! $is_front_page && is_home();
 
 		switch_to_blog( $this->obj->userblog_id );
 
-		if ( $is_home || $options->has_value( $this->get_language() ) ) {
+		if ( $is_front_page || $options->has_value( $this->get_language() ) ) {
 			$url = apply_filters( self::MSLS_GET_PERMALINK_HOOK, $options->get_permalink( $this->get_language() ), $this );
+		} elseif ( $is_posts_page ) {
+			$page_for_posts = (int) get_option( 'page_for_posts' );
+			if ( $page_for_posts > 0 ) {
+				$url = apply_filters( self::MSLS_GET_PERMALINK_HOOK, (string) get_permalink( $page_for_posts ), $this );
+			}
 		}
 
 		restore_current_blog();

includes/MslsOptions.php

@@ -416,8 +416,15 @@ public static function check_for_blog_slug( $url, $options ) {
 		if ( $permalink_structure ) {
 			list( $needle, ) = explode( '/%', $permalink_structure, 2 );
 
-			$url = str_replace( $needle, '', $url );
-			if ( is_main_site() && $options->with_front ) {
+			$stripped = false;
+			if ( '' !== $needle && str_starts_with( $url, $needle ) ) {
+				$rest = substr( $url, strlen( $needle ) );
+				if ( '' === $rest || '/' === $rest[0] ) {
+					$url      = '' === $rest ? '/' : $rest;
+					$stripped = true;
+				}
+			}
+			if ( is_main_site() && $options->with_front && $stripped ) {
 				$url = "{$needle}{$url}";
 			}
 		}

tests/phpunit/TestMslsBlog.php

@@ -52,7 +52,8 @@ public function test_get_frontpage(): void {
 		$collection->shouldReceive( 'get_current_blog_id' )->andReturn( 2 );
 
 		Functions\expect( 'msls_blog_collection' )->once()->andReturn( $collection );
-		Functions\expect( 'is_front_page' )->once()->andReturn( true );
+		Functions\expect( 'is_front_page' )->atLeast()->once()->andReturn( true );
+		Functions\expect( 'is_home' )->zeroOrMoreTimes()->andReturn( false );
 		Functions\expect( 'switch_to_blog' )->once();
 		Functions\expect( 'restore_current_blog' )->once();
 
@@ -70,7 +71,47 @@ public function test_get_url(): void {
 		$collection->shouldReceive( 'get_current_blog_id' )->andReturn( 2 );
 
 		Functions\expect( 'msls_blog_collection' )->once()->andReturn( $collection );
-		Functions\expect( 'is_front_page' )->once()->andReturn( false );
+		Functions\expect( 'is_front_page' )->atLeast()->once()->andReturn( false );
+		Functions\expect( 'is_home' )->atLeast()->once()->andReturn( false );
+		Functions\expect( 'switch_to_blog' )->once();
+		Functions\expect( 'restore_current_blog' )->once();
+
+		$this->assertEquals( $url, $this->MslsBlogFactory()->get_url( $option ) );
+	}
+
+	public function test_get_posts_page(): void {
+		$url = 'https://msls.co/sv/blogg/';
+
+		$option = \Mockery::mock( MslsOptions::class );
+		$option->shouldReceive( 'has_value' )->once()->andReturn( false );
+
+		$collection = \Mockery::mock( MslsBlogCollection::class );
+		$collection->shouldReceive( 'get_current_blog_id' )->andReturn( 2 );
+
+		Functions\expect( 'msls_blog_collection' )->once()->andReturn( $collection );
+		Functions\expect( 'is_front_page' )->atLeast()->once()->andReturn( false );
+		Functions\expect( 'is_home' )->atLeast()->once()->andReturn( true );
+		Functions\expect( 'switch_to_blog' )->once();
+		Functions\expect( 'restore_current_blog' )->once();
+		Functions\expect( 'get_option' )->atLeast()->once()->andReturn( 42 );
+		Functions\expect( 'get_permalink' )->once()->with( 42 )->andReturn( $url );
+
+		$this->assertEquals( $url, $this->MslsBlogFactory()->get_url( $option ) );
+	}
+
+	public function test_get_posts_page_with_translation(): void {
+		$url = 'https://msls.co/sv/blogg/';
+
+		$option = \Mockery::mock( MslsOptions::class );
+		$option->shouldReceive( 'get_permalink' )->once()->andReturn( $url );
+		$option->shouldReceive( 'has_value' )->once()->andReturn( true );
+
+		$collection = \Mockery::mock( MslsBlogCollection::class );
+		$collection->shouldReceive( 'get_current_blog_id' )->andReturn( 2 );
+
+		Functions\expect( 'msls_blog_collection' )->once()->andReturn( $collection );
+		Functions\expect( 'is_front_page' )->atLeast()->once()->andReturn( false );
+		Functions\expect( 'is_home' )->atLeast()->once()->andReturn( true );
 		Functions\expect( 'switch_to_blog' )->once();
 		Functions\expect( 'restore_current_blog' )->once();
 

tests/phpunit/TestMslsOptions.php

@@ -204,6 +204,9 @@ public static function provide_data_for_slug_check(): array {
 			array( 'https://msls.co/blog/2024/05/test', 'https://msls.co/blog/2024/05/test', true, true, true, '/blog/%year%/%monthnum%/%postname%/', true ),
 			array( 'https://msls.co/blog/test', 'https://msls.co/blog/test', true, true, true, '/%postname%/', true ),
 			array( 'https://msls.co/blog/test', 'https://msls.co/blog/test', true, true, true, '/blog/%postname%/', true ),
+			array( 'https://msls.co/blogg/', 'https://msls.co/blogg/', true, true, true, '/blog/%postname%/', false ),
+			array( 'https://msls.co/blogg/', 'https://msls.co/blogg/', true, true, true, '/blog/%postname%/', true ),
+			array( 'https://msls.co/blog/', 'https://msls.co/', true, true, true, '/blog/%postname%/', false ),
 		);
 	}