Raise exception for unsupported weight type. Update tests

changes/348.general.rst

@@ -0,0 +1 @@
+Updated ``build_driz_weight`` to raise an exception when requested ``weight_type`` is not supported.

src/stcal/resample/utils.py

@@ -144,9 +144,15 @@ def build_driz_weight(model, weight_type=None, good_bits=None,
         exptime, s = get_tmeasure(model)
         result = exptime * dqmask
 
-    else:
+    elif weight_type is None:
         result = np.ones(data.shape, dtype=data.dtype) * dqmask
 
+    else:
+        raise ValueError(
+            f"Invalid weight type: {repr(weight_type)}. "
+            "Allowed weight types are 'ivm', 'exptime', or None."
+        )
+
     return result.astype(np.float32)
 
 

tests/resample/test_resample.py

@@ -88,13 +88,9 @@ def test_resample_mostly_defaults(weight_type):
 
 
 @pytest.mark.parametrize(
-    "compute_err,weight_type",
-    [
-        ("from_var", "ivm-smed"),
-        ("driz_err", "ivm-med5")
-    ]
+    "compute_err", ["from_var", "driz_err"]
 )
-def test_resample_compute_error_mode(compute_err, weight_type):
+def test_resample_compute_error_mode(compute_err):
     crval = (150.0, 2.0)
     crpix = (500.0, 500.0)
     shape = (1000, 1000)
@@ -114,7 +110,7 @@ def test_resample_compute_error_mode(compute_err, weight_type):
     resample = Resample(
         n_input_models=nmodels,
         output_wcs=output_model,
-        weight_type=weight_type,
+        weight_type="ivm",
         compute_err=compute_err,
     )
     resample.dq_flag_name_map = JWST_DQ_FLAG_DEF

tests/resample/test_resample_utils.py

@@ -148,3 +148,13 @@ def test_build_driz_weight_zeros(weight_type):
     weight_map = build_driz_weight(model, weight_type=weight_type)
 
     assert_array_equal(weight_map, 1)
+
+
+@pytest.mark.parametrize("weight_type", ["ivm-smed", "ivm-med5"])
+def test_unsupported_weight_type(weight_type):
+    model = make_input_model((10, 10))
+    with pytest.raises(ValueError) as err_info:
+        build_driz_weight(model, weight_type=weight_type)
+    assert str(err_info.value).startswith(
+        f"Invalid weight type: {repr(weight_type)}."
+    )