feat(dask): support connect() with no arguments

ibis/backends/dask/__init__.py

@@ -30,14 +30,14 @@ class Backend(BasePandasBackend):
 
     def do_connect(
         self,
-        dictionary: MutableMapping[str, dd.DataFrame],
+        dictionary: MutableMapping[str, dd.DataFrame] | None = None,
     ) -> None:
         """Construct a Dask backend client from a dictionary of data sources.
 
         Parameters
         ----------
         dictionary
-            Mapping from `str` table names to Dask DataFrames.
+            An optional mapping from `str` table names to Dask DataFrames.
 
         Examples
         --------
@@ -52,6 +52,9 @@ def do_connect(
         # register dispatchers
         from ibis.backends.dask import udf  # noqa: F401
 
+        if dictionary is None:
+            dictionary = {}
+
         for k, v in dictionary.items():
             if not isinstance(v, (dd.DataFrame, pd.DataFrame)):
                 raise TypeError(

ibis/backends/dask/tests/test_client.py

@@ -37,6 +37,11 @@ def table(client):
     return client.table('df')
 
 
+def test_connect_no_args():
+    con = ibis.dask.connect()
+    assert dict(con.tables) == {}
+
+
 def test_client_table(table):
     assert isinstance(table.op(), ibis.expr.operations.DatabaseTable)
     assert isinstance(table.op(), DaskTable)