Fix truediv joining against absolute URL with no path (#857)

When joining path elements against an absolute URL, ensure that
the resulting path starts with a slash.

CHANGES/854.bugfix.rst

@@ -0,0 +1 @@
+Fix regression with truediv and absolute URLs with empty paths causing the raw path to lack the leading ``/``.

tests/test_url.py

@@ -690,23 +690,27 @@ def test_clear_query_on_getting_parent_toplevel():
 
 
 def test_div_root():
- url = URL("http://example.com")
- assert str(url / "path" / "to") == "http://example.com/path/to"
+ url = URL("http://example.com") / "path" / "to"
+ assert str(url) == "http://example.com/path/to"
+ assert url.raw_path == "/path/to"
 
 
 def test_div_root_with_slash():
- url = URL("http://example.com/")
- assert str(url / "path" / "to") == "http://example.com/path/to"
+ url = URL("http://example.com/") / "path" / "to"
+ assert str(url) == "http://example.com/path/to"
+ assert url.raw_path == "/path/to"
 
 
 def test_div():
- url = URL("http://example.com/path")
- assert str(url / "to") == "http://example.com/path/to"
+ url = URL("http://example.com/path") / "to"
+ assert str(url) == "http://example.com/path/to"
+ assert url.raw_path == "/path/to"
 
 
 def test_div_with_slash():
- url = URL("http://example.com/path/")
- assert str(url / "to") == "http://example.com/path/to"
+ url = URL("http://example.com/path/") / "to"
+ assert str(url) == "http://example.com/path/to"
+ assert url.raw_path == "/path/to"
 
 
 def test_div_path_starting_from_slash_is_forbidden():

yarl/_url.py

@@ -734,6 +734,10 @@ def _make_child(self, segments, encoded=False):
  parsed = [*old_path.rstrip("/").split("/"), *parsed]
  if self.is_absolute():
  parsed = _normalize_path_segments(parsed)
+ if parsed and parsed[0] != "":
+ # inject a leading slash when adding a path to an absolute URL
+ # where there was none before
+ parsed = ["", *parsed]
  new_path = "/".join(parsed)
  return URL(
  self._val._replace(path=new_path, query="", fragment=""), encoded=True