Do not double-decode username and password in SQLAlchemy URL

tests/unit/sqlalchemy/test_dialect.py

@@ -271,6 +271,19 @@ def test_trino_connection_basic_auth():
     assert cparams['auth']._password == password
 
 
+def test_trino_connection_basic_auth_with_plus_in_credentials():
+    # SQLAlchemy's make_url already percent-decodes the userinfo, so the dialect
+    # must not run it through unquote_plus again (that turns a literal '+' into a space).
+    dialect = TrinoDialect()
+    url = make_url("trino://user%2Bname:pass%2Bword@host")
+    _, cparams = dialect.create_connect_args(url)
+
+    assert cparams['user'] == 'user+name'
+    assert isinstance(cparams['auth'], BasicAuthentication)
+    assert cparams['auth']._username == 'user+name'
+    assert cparams['auth']._password == 'pass+word'
+
+
 def test_trino_connection_jwt_auth():
     dialect = TrinoDialect()
     access_token = 'sample-token'

trino/sqlalchemy/dialect.py

@@ -127,13 +127,17 @@ def create_connect_args(self, url: URL) -> Tuple[Sequence[Any], Mapping[str, Any
         else:
             raise ValueError(f"Unexpected database format {url.database}")
 
+        # SQLAlchemy's make_url already percent-decodes the userinfo, so we use the
+        # username and password as-is. Running them through unquote_plus again would
+        # corrupt a literal '+' into a space (form-encoding only applies to the query
+        # string, not to the userinfo component).
         if url.username:
-            kwargs["user"] = unquote_plus(url.username)
+            kwargs["user"] = url.username
 
         if url.password:
             if not url.username:
                 raise ValueError("Username is required when specify password in connection URL")
-            kwargs["auth"] = BasicAuthentication(unquote_plus(url.username), unquote_plus(url.password))
+            kwargs["auth"] = BasicAuthentication(url.username, url.password)
 
         if "access_token" in url.query:
             kwargs["auth"] = JWTAuthentication(unquote_plus(url.query["access_token"]))