feat(pandas, polars, dask, datafusion): enable create local backends …

…with empty url (#8860)

support empty URL for local backends in ibis.connect()

## Issues closed
* Resolves #8450

ibis/backends/__init__.py

@@ -1458,5 +1458,21 @@ class NoUrl:
 
     name: str
 
-    def _from_url(self, url: str, **_) -> ir.Table:
-        raise NotImplementedError(self.name)
+    def _from_url(self, url: str, **kwargs) -> BaseBackend:
+        """Connect to the backend with empty url.
+
+        Parameters
+        ----------
+        url : str
+            The URL with which to connect to the backend. This parameter is not used
+            in this method but is kept for consistency.
+        kwargs
+            Additional keyword arguments.
+
+        Returns
+        -------
+        BaseBackend
+            A backend instance
+
+        """
+        return self.connect(**kwargs)

ibis/backends/tests/test_client.py

@@ -711,12 +711,12 @@ def test_unsigned_integer_type(con, temp_table):
         ),
         param(
             "dask://",
-            marks=[mark.dask, mark.xfail(raises=NotImplementedError)],
+            marks=mark.dask,
             id="dask",
         ),
         param(
             "datafusion://",
-            marks=[mark.datafusion, mark.xfail(raises=NotImplementedError)],
+            marks=mark.datafusion,
             id="datafusion",
         ),
         param(
@@ -731,9 +731,14 @@ def test_unsigned_integer_type(con, temp_table):
         ),
         param(
             "pandas://",
-            marks=[mark.pandas, mark.xfail(raises=NotImplementedError)],
+            marks=mark.pandas,
             id="pandas",
         ),
+        param(
+            "polars://",
+            marks=mark.polars,
+            id="polars",
+        ),
         param(
             "postgres://postgres:postgres@localhost:5432",
             marks=mark.postgres,