Restore the ability to watch files through relative symlinks

Restore the ability to watch files through relative symlinks
(i.e. symlinks that have a non-absolute path as the target)

This was not fully fixed in #2427.

Switch from os.path.realpath to pathlib.Path.resolve

mkdocs/livereload/__init__.py

@@ -101,29 +101,26 @@ class LiveReloadServer(socketserver.ThreadingMixIn, wsgiref.simple_server.WSGISe
 
         def schedule(path):
             seen.add(path)
-            if os.path.isfile(path):
+            if path.is_file():
                 # Watchdog doesn't support watching files, so watch its directory and filter by path
                 handler = watchdog.events.FileSystemEventHandler()
-                handler.on_any_event = lambda event: callback(event, allowed_path=path)
+                handler.on_any_event = lambda event: callback(event, allowed_path=os.fspath(path))
 
-                parent = os.path.dirname(path)
+                parent = path.parent
                 log.debug(f"Watching file '{path}' through directory '{parent}'")
                 self.observer.schedule(handler, parent)
             else:
                 log.debug(f"Watching directory '{path}'")
                 self.observer.schedule(dir_handler, path, recursive=recursive)
 
-        schedule(os.path.realpath(path))
+        schedule(pathlib.Path(path).resolve())
 
         def watch_symlink_targets(path_obj):  # path is os.DirEntry or pathlib.Path
             if path_obj.is_symlink():
-                # The extra `readlink` is needed due to https://bugs.python.org/issue9949
-                target = os.path.realpath(os.readlink(os.fspath(path_obj)))
-                if target in seen or not os.path.exists(target):
+                path_obj = pathlib.Path(path_obj).resolve()
+                if path_obj in seen or not path_obj.exists():
                     return
-                schedule(target)
-
-                path_obj = pathlib.Path(target)
+                schedule(path_obj)
 
             if path_obj.is_dir() and recursive:
                 with os.scandir(os.fspath(path_obj)) as scan:

mkdocs/tests/livereload_tests.py

@@ -3,6 +3,7 @@
 import contextlib
 import email
 import io
+import os
 import sys
 import threading
 import time
@@ -496,6 +497,28 @@ class BuildTests(unittest.TestCase):
             Path(tmp_dir, "file_dest_unused.md").write_text("edited")
             self.assertFalse(started_building.wait(timeout=0.2))
 
+    @tempdir(prefix="site_dir")
+    @tempdir(["docs/unused.md", "README.md"], prefix="origin_dir")
+    def test_watches_through_relative_symlinks(self, origin_dir, site_dir):
+        docs_dir = Path(origin_dir, "docs")
+        old_cwd = os.getcwd()
+        os.chdir(docs_dir)
+        try:
+            Path(docs_dir, "README.md").symlink_to(Path("..", "README.md"))
+        except NotImplementedError:  # PyPy on Windows
+            self.skipTest("Creating symlinks not supported")
+        finally:
+            os.chdir(old_cwd)
+
+        started_building = threading.Event()
+
+        with testing_server(docs_dir, started_building.set) as server:
+            server.watch(docs_dir)
+            time.sleep(0.01)
+
+            Path(origin_dir, "README.md").write_text("edited")
+            self.assertTrue(started_building.wait(timeout=10))
+
     @tempdir()
     def test_watch_with_broken_symlinks(self, docs_dir):
         Path(docs_dir, "subdir").mkdir()
@@ -503,7 +526,6 @@ class BuildTests(unittest.TestCase):
         try:
             if sys.platform != "win32":
                 Path(docs_dir, "subdir", "circular").symlink_to(Path(docs_dir))
-            Path(docs_dir, "self_link").symlink_to(Path(docs_dir, "self_link"))
 
             Path(docs_dir, "broken_1").symlink_to(Path(docs_dir, "oh no"))
             Path(docs_dir, "broken_2").symlink_to(Path(docs_dir, "oh no"), target_is_directory=True)