Fix database URLs when netloc is empty

Author: lovelydinosaur

databases/core.py

@@ -246,6 +246,11 @@ async def rollback(self) -> None:
             await self._connection.__aexit__()
 
 
+class _EmptyNetloc(str):
+    def __bool__(self):
+        return True
+
+
 class DatabaseURL:
     def __init__(self, url: typing.Union[str, "DatabaseURL"]):
         self._url = str(url)
@@ -282,6 +287,10 @@ def hostname(self) -> typing.Optional[str]:
     def port(self) -> typing.Optional[int]:
         return self.components.port
 
+    @property
+    def netloc(self) -> typing.Optional[str]:
+        return self.components.netloc
+
     @property
     def database(self) -> str:
         return self.components.path.lstrip("/")
@@ -317,6 +326,11 @@ def replace(self, **kwargs: typing.Any) -> "DatabaseURL":
             driver = kwargs.pop("driver", self.driver)
             kwargs["scheme"] = f"{dialect}+{driver}" if driver else dialect
 
+        if not kwargs.get("netloc", self.netloc):
+            # Using an empty string that evaluates as True means we end
+            # up with URLs like `sqlite:///database` instead of `sqlite:/database`
+            kwargs["netloc"] = _EmptyNetloc()
+
         components = self.components._replace(**kwargs)
         return self.__class__(components.geturl())
 

tests/test_database_url.py

@@ -40,3 +40,9 @@ def test_replace_database_url_components():
     new = u.replace(port=123)
     assert new.port == 123
     assert str(new) == "postgresql://localhost:123/mydatabase"
+
+    u = DatabaseURL("sqlite:///mydatabase")
+    assert u.database == "mydatabase"
+    new = u.replace(database="test_" + u.database)
+    assert new.database == "test_mydatabase"
+    assert str(new) == "sqlite:///test_mydatabase"