Add support for alternate hreflang link

tests/tree/test_xml_exts.py

@@ -105,3 +105,56 @@ def test_xml_image(self, requests_mock):
         print(tree)
 
         assert tree == expected_sitemap_tree
+
+    def test_xml_hreflang(self, requests_mock):
+        requests_mock.add_matcher(TreeTestBase.fallback_to_404_not_found_matcher)
+
+        requests_mock.get(
+            self.TEST_BASE_URL + "/robots.txt",
+            headers={"Content-Type": "text/plain"},
+            text=textwrap.dedent(
+                f"""
+                User-agent: *
+                Disallow: /whatever
+
+                Sitemap: {self.TEST_BASE_URL}/sitemap.xml
+
+            """
+            ).strip(),
+        )
+
+        requests_mock.get(
+            self.TEST_BASE_URL + "/sitemap.xml",
+            headers={"Content-Type": "text/xml"},
+            text=textwrap.dedent(
+                f"""
+                <?xml version="1.0" encoding="UTF-8"?>
+                <urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" xmlns:xhtml="http://www.w3.org/1999/xhtml">
+                    <url>
+                        <loc>{self.TEST_BASE_URL}/en/page</loc>
+                        <lastmod>{self.TEST_DATE_STR_ISO8601}</lastmod>
+                        <changefreq>monthly</changefreq>
+                        <priority>0.8</priority>
+                        <xhtml:link rel="alternate" hreflang="fr-FR" href="{self.TEST_BASE_URL}/fr/page"/>
+                    </url>
+                    <url>
+                        <loc>{self.TEST_BASE_URL}/fr/page</loc>
+                        <lastmod>{self.TEST_DATE_STR_ISO8601}</lastmod>
+                        <changefreq>monthly</changefreq>
+                        <priority>0.8</priority>
+                        <xhtml:link rel="alternate" hreflang="en-GB" href="{self.TEST_BASE_URL}/en/page"/>
+                    </url>
+                </urlset>
+                """
+            ).strip()
+        )
+
+        tree = sitemap_tree_for_homepage(self.TEST_BASE_URL)
+
+        pages = list(tree.all_pages())
+        assert pages[0].alternates == [
+            ("fr-FR", f"{self.TEST_BASE_URL}/fr/page"),
+        ]
+        assert pages[1].alternates == [
+            ("en-GB", f"{self.TEST_BASE_URL}/en/page"),
+        ]

usp/fetch_parse.py

@@ -643,6 +643,7 @@ class Page:
             "news_keywords",
             "news_stock_tickers",
             "images",
+            "alternates"
         ]
 
         def __init__(self):
@@ -659,6 +660,7 @@ def __init__(self):
             self.news_keywords = None
             self.news_stock_tickers = None
             self.images = []
+            self.alternates = []
 
         def __hash__(self):
             return hash(
@@ -763,13 +765,18 @@ def page(self) -> Optional[SitemapPage]:
                     for image in self.images
                 ]
 
+            alternates = None
+            if len(self.alternates) > 0:
+                alternates = self.alternates
+
             return SitemapPage(
                 url=url,
                 last_modified=last_modified,
                 change_frequency=change_frequency,
                 priority=priority,
                 news_story=sitemap_news_story,
                 images=sitemap_images,
+                alternates=alternates,
             )
 
     __slots__ = ["_current_page", "_pages", "_page_urls", "_current_image"]
@@ -801,6 +808,15 @@ def xml_element_start(self, name: str, attrs: Dict[str, str]) -> None:
                     "Page is expected to be set before <image:image>."
                 )
             self._current_image = self.Image()
+        elif name == "link":
+            if not self._current_page:
+                raise SitemapXMLParsingException(
+                    "Page is expected to be set before <link>."
+                )
+            if "hreflang" not in attrs or "href" not in attrs:
+                log.warning(f"<link> element is missing hreflang or href attributes: {attrs}.")
+
+            self._current_page.alternates.append((attrs["hreflang"], attrs["href"]))
 
     def __require_last_char_data_to_be_set(self, name: str) -> None:
         if not self._last_char_data:

usp/objects/page.py

@@ -3,7 +3,7 @@
 import datetime
 from decimal import Decimal
 from enum import Enum, unique
-from typing import List, Optional
+from typing import List, Optional, Tuple
 
 SITEMAP_PAGE_DEFAULT_PRIORITY = Decimal("0.5")
 """Default sitemap page priority, as per the spec."""
@@ -331,6 +331,7 @@ class SitemapPage:
         "__change_frequency",
         "__news_story",
         "__images",
+        "__alternates",
     ]
 
     def __init__(
@@ -341,6 +342,7 @@ def __init__(
         change_frequency: Optional[SitemapPageChangeFrequency] = None,
         news_story: Optional[SitemapNewsStory] = None,
         images: Optional[List[SitemapImage]] = None,
+        alternates: Optional[List[Tuple[str, str]]] = None,
     ):
         """
         Initialize a new sitemap-derived page.
@@ -357,6 +359,7 @@ def __init__(
         self.__change_frequency = change_frequency
         self.__news_story = news_story
         self.__images = images
+        self.__alternates = alternates
 
     def __eq__(self, other) -> bool:
         if not isinstance(other, SitemapPage):
@@ -380,6 +383,9 @@ def __eq__(self, other) -> bool:
         if self.images != other.images:
             return False
 
+        if self.alternates != other.alternates:
+            return False
+
         return True
 
     def __hash__(self):
@@ -449,3 +455,8 @@ def news_story(self) -> Optional[SitemapNewsStory]:
     def images(self) -> Optional[List[SitemapImage]]:
         """Get the images attached to the URL."""
         return self.__images
+
+    @property
+    def alternates(self) -> Optional[List[Tuple[str, str]]]:
+        """Get the alternate URLs for the URL."""
+        return self.__alternates