Fix a regression of using REFCASE with extension

src/ert/config/_read_summary.py

@@ -211,6 +211,11 @@ def _find_file_matching(
 
 
 def _get_summary_filenames(filepath: str) -> Tuple[str, str]:
+    if filepath.lower().endswith(".data"):
+        # For backwards compatability, it is
+        # allowed to give REFCASE and ECLBASE both
+        # with and without .DATA extensions
+        filepath = filepath[:-5]
     summary = _find_file_matching("unified summary file", filepath, _is_unsmry)
     spec = _find_file_matching("smspec file", filepath, _is_smspec)
     return summary, spec

tests/unit_tests/config/test_observations.py

@@ -682,21 +682,22 @@ def test_that_out_of_bounds_segments_are_truncated(tmpdir, start, stop, message)
             ErtConfig.from_file("config.ert")
 
 
+@pytest.mark.parametrize("with_ext", [True, False])
 @pytest.mark.parametrize(
     "keys",
     [
         [("FOPR", "SM3/DAY", None), ("FOPRH", "SM3/DAY", None)],
         [("WWIR", "SM3/DAY", "WNAME"), ("WWIRH", "SM3/DAY", "WNAME")],
     ],
 )
-def test_that_history_observations_are_loaded(tmpdir, keys):
+def test_that_history_observations_are_loaded(tmpdir, keys, with_ext):
     with tmpdir.as_cwd():
         config = dedent(
-            """
+            f"""
         NUM_REALIZATIONS 2
 
         ECLBASE ECLIPSE_CASE
-        REFCASE ECLIPSE_CASE
+        REFCASE ECLIPSE_CASE{".DATA" if with_ext else ""}
         OBS_CONFIG observations
         """
         )