Ignore http credentials with empty usernames

See-also: jaraco/keyring#668 jaraco/keyring#687

docs/repositories.md

@@ -511,6 +511,17 @@ You can prevent this by adding double dashes to prevent any following argument f
 poetry config -- http-basic.pypi myUsername -myPasswordStartingWithDash
 ```
 
+{{% note %}}
+In some cases like that of [Gemfury](https://gemfury.com/help/errors/repo-url-password/) repositories, it might be
+required to set an empty password. This is supported by Poetry.
+
+```bash
+poetry config http-basic.foo <TOKEN> ""
+```
+
+**Note:** Usernames cannot be empty.  Attempting to use an empty username can result in an unpredictable failure.
+{{% /note %}}
+
 ## Certificates
 
 ### Custom certificate authority and mutual TLS authentication

src/poetry/utils/password_manager.py

@@ -196,23 +196,17 @@ def get_http_auth(self, repo_name: str) -> dict[str, str | None] | None:
         username = self._config.get(f"http-basic.{repo_name}.username")
         password = self._config.get(f"http-basic.{repo_name}.password")
 
-        # we only return None if both values are None or ""
-        # password can be None at this stage with the username ""
-        if (username is password is None) or (username == password == ""):
+        if not username:
             return None
 
         if not password:
             if self.use_keyring:
                 password = self.keyring.get_password(repo_name, username)
             elif not username:
-                # at this tage if username is "" or None, auth is invalid
                 return None
 
-        if not username and not password:
-            return None
-
         return {
-            "username": username or "",
+            "username": username,
             "password": password or "",
         }
 

tests/utils/test_authenticator.py

@@ -153,7 +153,7 @@ def test_authenticator_uses_empty_strings_as_default_password(
     assert request.headers["Authorization"] == f"Basic {basic_auth}"
 
 
-def test_authenticator_uses_empty_strings_as_default_username(
+def test_authenticator_ignores_empty_strings_as_default_username(
     config: Config,
     mock_remote: None,
     repo: dict[str, dict[str, str]],
@@ -170,8 +170,7 @@ def test_authenticator_uses_empty_strings_as_default_username(
     authenticator.request("get", "https://foo.bar/files/foo-0.1.0.tar.gz")
 
     request = http.last_request()
-    basic_auth = base64.b64encode(b":bar").decode()
-    assert request.headers["Authorization"] == f"Basic {basic_auth}"
+    assert request.headers["Authorization"] is None
 
 
 def test_authenticator_falls_back_to_keyring_url(

tests/utils/test_password_manager.py

@@ -40,7 +40,7 @@ def test_set_http_password(
     ("username", "password", "is_valid"),
     [
         ("bar", "baz", True),
-        ("", "baz", True),
+        ("", "baz", False),
         ("bar", "", True),
         ("", "", False),
     ],
@@ -134,7 +134,7 @@ def test_set_http_password_with_unavailable_backend(
     ("username", "password", "is_valid"),
     [
         ("bar", "baz", True),
-        ("", "baz", True),
+        ("", "baz", False),
         ("bar", "", True),
         ("", "", False),
     ],