website: Add Python script to check relative links.

website/Makefile

@@ -24,6 +24,9 @@ docset: $(TOOL_BINS) $(HTMLS)
 publish: gen
 	rsync -aLv --delete ./_dst/ $(PUBLISH_DIR)/
 
+check-rellinks: gen
+	python3 tools/check-rellinks.py $(DST_DIR)
+
 clean:
 	rm -rf $(TOOL_BINS) $(HTMLS) $(DST_DIR) $(DOCSET_TMP_DIR) $(DOCSET_DST_DIR)
 

website/tools/check-rellinks.py

@@ -0,0 +1,68 @@
+import dataclasses
+import glob
+import os
+import os.path
+import sys
+import urllib.parse
+
+import bs4
+
+@dataclasses.dataclass
+class Link:
+    href: str
+    parsed: urllib.parse.ParseResult
+
+def main(args):
+    if len(args) != 2:
+        print('Usage: check-rellinks dir')
+        sys.exit(1)
+    os.chdir(args[1])
+
+    filenames = glob.glob('**/*.html', recursive=True)
+    targets = {}
+    rellinks = {}
+    for filename in filenames:
+        with open(filename) as f:
+            soup = bs4.BeautifulSoup(f, 'html.parser')
+        links = [Link(href=e['href'], parsed=urllib.parse.urlparse(e['href']))
+                 for e in soup.find_all('a', href=True)]
+        rellinks[filename] = [link for link in links if link.parsed.scheme == '']
+        targets[filename] = [e['id'] for e in soup.find_all(id=True)]
+
+    def check(path, fragment):
+        if path.endswith('.atom') and fragment == '':
+            return True
+        return path in targets and (fragment == '' or fragment in targets[path])
+
+    has_broken = False
+
+    for filename in rellinks:
+        if filename.endswith('-release-notes.html'):
+            continue
+        dirname = os.path.dirname(filename)
+        broken_links = []
+        for link in rellinks[filename]:
+            path = link.parsed.path
+            if path == '':
+                path = filename
+            else:
+                if os.path.splitext(path)[1] == '':
+                    path += '/index.html'
+                if path.startswith('/'):
+                    path = path.lstrip('/')
+                else:
+                    path = os.path.normpath(os.path.join(dirname, path))
+            if not check(path, link.parsed.fragment):
+                broken_links.append(link.href)
+        if broken_links:
+            if not has_broken:
+                print('Found broken links:')
+                has_broken = True
+            print(filename)
+            for link in broken_links:
+                print(f'    {link}')
+    if has_broken:
+        sys.exit(1)
+
+if __name__ == '__main__':
+    main(sys.argv)