DEP: Assigning CRS to a GeoDataFrame without a geometry column (#2268)

* DEP: convert crs without geom col warnings to errors

* TST: update tests to now reflect new errors

* TST: fix tests to still test old behaviour as well

geopandas/geodataframe.py

@@ -189,11 +189,10 @@ class GeoDataFrame(GeoPandasBase, DataFrame):
             self.set_geometry(geometry, inplace=True)
 
         if geometry is None and crs:
-            warnings.warn(
-                "Assigning CRS to a GeoDataFrame without a geometry column is now "
-                "deprecated and will not be supported in the future.",
-                FutureWarning,
-                stacklevel=2,
+            raise ValueError(
+                "Assigning CRS to a GeoDataFrame without a geometry column is not "
+                "supported. Supply geometry using the 'geometry=' keyword argument, "
+                "or by providing a DataFrame with column name 'geometry'",
             )
 
     def __setattr__(self, attr, val):
@@ -442,13 +441,11 @@ class GeoDataFrame(GeoPandasBase, DataFrame):
     def crs(self, value):
         """Sets the value of the crs"""
         if self._geometry_column_name not in self:
-            warnings.warn(
-                "Assigning CRS to a GeoDataFrame without a geometry column is now "
-                "deprecated and will not be supported in the future.",
-                FutureWarning,
-                stacklevel=4,
+            raise ValueError(
+                "Assigning CRS to a GeoDataFrame without a geometry column is not "
+                "supported. Use GeoDataFrame.set_geometry to set the active "
+                "geometry column.",
             )
-            self._crs = None if not value else CRS.from_user_input(value)
         else:
             if hasattr(self.geometry.values, "crs"):
                 self.geometry.values.crs = value

geopandas/tests/test_crs.py

@@ -242,9 +242,13 @@ class TestGeometryArrayCRS:
         assert df.geometry.crs == self.wgs
         assert df.geometry.values.crs == self.wgs
 
-        df = GeoDataFrame(self.geoms, columns=["geom"], crs=27700)
-        assert df.crs == self.osgb
-        df = df.set_geometry("geom")
+        with pytest.raises(ValueError, match="Assigning CRS to a GeoDataFrame without"):
+            GeoDataFrame(self.geoms, columns=["geom"], crs=27700)
+        with pytest.raises(ValueError, match="Assigning CRS to a GeoDataFrame without"):
+            GeoDataFrame(crs=27700)
+
+        df = GeoDataFrame(self.geoms, columns=["geom"])
+        df = df.set_geometry("geom", crs=27700)
         assert df.crs == self.osgb
         assert df.geometry.crs == self.osgb
         assert df.geometry.values.crs == self.osgb
@@ -256,14 +260,8 @@ class TestGeometryArrayCRS:
         assert df.geometry.crs == self.osgb
         assert df.geometry.values.crs == self.osgb
 
-        df = GeoDataFrame(crs=27700)
-        df = df.set_geometry(self.geoms)
-        assert df.crs == self.osgb
-        assert df.geometry.crs == self.osgb
-        assert df.geometry.values.crs == self.osgb
-
         # new geometry with set CRS has priority over GDF CRS
-        df = GeoDataFrame(crs=27700)
+        df = GeoDataFrame(geometry=self.geoms, crs=27700)
         df = df.set_geometry(self.geoms, crs=4326)
         assert df.crs == self.wgs
         assert df.geometry.crs == self.wgs
@@ -341,14 +339,18 @@ class TestGeometryArrayCRS:
         "scalar", [None, Point(0, 0), LineString([(0, 0), (1, 1)])]
     )
     def test_scalar(self, scalar):
-        with pytest.warns(FutureWarning):
-            df = GeoDataFrame()
-            df.crs = 4326
+        df = GeoDataFrame()
         df["geometry"] = scalar
+        df.crs = 4326
         assert df.crs == self.wgs
         assert df.geometry.crs == self.wgs
         assert df.geometry.values.crs == self.wgs
 
+    def test_crs_with_no_geom_fails(self):
+        with pytest.raises(ValueError, match="Assigning CRS to a GeoDataFrame without"):
+            df = GeoDataFrame()
+            df.crs = 4326
+
     def test_read_file(self):
         nybb_filename = datasets.get_path("nybb")
         df = read_file(nybb_filename)
@@ -579,21 +581,6 @@ class TestGeometryArrayCRS:
         assert merged.geom.values.crs == self.osgb
         assert merged.crs == self.osgb
 
-    # CRS should be assigned to geometry
-    def test_deprecation(self):
-        with pytest.warns(FutureWarning):
-            df = GeoDataFrame([], crs=27700)
-
-        # https://github.com/geopandas/geopandas/issues/1548
-        # ensure we still have converted the crs value to a CRS object
-        assert isinstance(df.crs, pyproj.CRS)
-
-        with pytest.warns(FutureWarning):
-            df = GeoDataFrame([])
-            df.crs = 27700
-
-        assert isinstance(df.crs, pyproj.CRS)
-
     # make sure that geometry column from list has CRS (__setitem__)
     def test_setitem_geometry(self):
         arr = from_shapely(self.geoms, crs=27700)