Add warnings and test for them.

Author: samcunliffe

src/napari_matplotlib/tests/test_util.py

@@ -28,18 +28,19 @@ def test_get_size_from_css(mocker):
         }
         """
     mocker.patch("napari.qt.get_current_stylesheet").return_value = test_css
-    assert from_css_get_size_of("Flibble", (1, 1)) == QSize(123, 456)
+    assert from_css_get_size_of("Flibble", (1, 2)) == QSize(123, 456)
 
 
 def test_fallback_if_missing_dimensions(mocker):
     """Test fallback if given something that doesn't have dimensions"""
     test_css = " Flobble { background-color: rgb(0, 97, 163); } "
     mocker.patch("napari.qt.get_current_stylesheet").return_value = test_css
-    assert from_css_get_size_of("Flobble", (1, 1)) == QSize(1, 1)
+    with pytest.warns(RuntimeWarning, match="Unable to find DimensionToken"):
+        assert from_css_get_size_of("Flobble", (1, 2)) == QSize(1, 2)
 
 
 def test_fallback_if_prelude_not_in_css():
     """Test fallback if given something not in the css"""
-    assert from_css_get_size_of("AQButtonThatDoesntExist", (1, 1)) == QSize(
-        1, 1
-    )
+    doesntexist = "AQButtonThatDoesntExist"
+    with pytest.warns(RuntimeWarning, match=f"Unable to find {doesntexist}"):
+        assert from_css_get_size_of(doesntexist, (1, 2)) == QSize(1, 2)

src/napari_matplotlib/util.py

@@ -1,4 +1,5 @@
 from typing import List, Optional, Tuple, Union
+from warnings import warn
 
 import napari.qt
 import tinycss2
@@ -67,6 +68,7 @@ def _get_dimension(
             and name.value == id_name
         ):
             return value.int_value
+    warn(f"Unable to find DimensionToken for {id_name}", RuntimeWarning)
     return None
 
 
@@ -95,4 +97,9 @@ def from_css_get_size_of(
             h = _get_dimension(rule.content, "max-height")
             if w and h:
                 return QSize(w, h)
+    warn(
+        f"Unable to find {qt_element_name} or unable to find its size in "
+        f"the current Napari stylesheet, falling back to {fallback}",
+        RuntimeWarning,
+    )
     return QSize(*fallback)