Box, Position: Fix validation of shade_offset and refpoint

pygmt/params/box.py

@@ -70,7 +70,7 @@ def _validate(self):
             )
 
         # shade_offset must be a sequence of two values or None.
-        if self.shade_offset and not (
+        if self.shade_offset is not None and not (
             is_nonstr_iter(self.shade_offset) and len(self.shade_offset) == 2
         ):
             raise GMTValueError(
@@ -91,7 +91,7 @@ def _shade(self) -> list[str | float] | None:
         """
         Shading for the box, formatted as a list of 1-3 values, or None.
         """
-        _shade_offset = self.shade_offset or []
+        _shade_offset = [] if self.shade_offset is None else self.shade_offset
         return [v for v in (*_shade_offset, self.shade_fill) if v is not None] or None
 
     @property

pygmt/params/position.py

@@ -180,7 +180,10 @@ def _validate(self):
                         reason="Expect a sequence of two values.",
                     )
             case "inside" | "outside":
-                if self.refpoint not in _valid_anchors:
+                if (
+                    not isinstance(self.refpoint, str)
+                    or self.refpoint not in _valid_anchors
+                ):
                     raise GMTValueError(
                         self.refpoint,
                         description="reference point",

pygmt/tests/test_params_box.py

@@ -2,6 +2,7 @@
 Test the Box class.
 """
 
+import numpy as np
 import pytest
 from pygmt.exceptions import GMTParameterError, GMTValueError
 from pygmt.params import Box
@@ -57,3 +58,13 @@ def test_params_box_invalid_innerborder():
     """
     with pytest.raises(GMTParameterError):
         _ = str(Box(inner_gap="2p"))
+
+
+def test_params_box_shade_offset_array_like():
+    """
+    Test that shade_offset accepts numpy arrays and rejects empty sequences.
+    """
+    assert str(Box(shade_offset=np.array([1, 2]))) == "+s1/2"
+    assert str(Box(shade_offset=np.array([1, 2]), shade_fill="red")) == "+s1/2/red"
+    with pytest.raises(GMTValueError):
+        Box(shade_offset=[])

pygmt/tests/test_params_position.py

@@ -59,3 +59,12 @@ def test_params_position_invalid_anchor():
     """
     with pytest.raises(GMTValueError):
         Position((10, 20), cstype="mapcoords", anchor="XX")
+
+
+def test_params_position_unhashable_justification_code():
+    """
+    Test that an unhashable refpoint raises GMTValueError rather than TypeError.
+    """
+    for cstype in ("inside", "outside"):
+        with pytest.raises(GMTValueError):
+            Position(["T", "L"], cstype=cstype)