[processing] Fix bar and box plot exception when category field has N…

…ULL values

python/plugins/processing/algs/qgis/BarPlot.py

@@ -29,7 +29,8 @@
 import plotly.graph_objs as go
 
 
-from qgis.core import (QgsProcessingParameterFeatureSource,
+from qgis.core import (QgsFeatureRequest,
+                       QgsProcessingParameterFeatureSource,
                        QgsProcessingParameterField,
                        QgsProcessingException,
                        QgsProcessingParameterFileDestination)
@@ -83,7 +84,7 @@ def processAlgorithm(self, parameters, context, feedback):
 
         values = vector.values(source, valuefieldname)
 
-        x_var = [i[namefieldname] for i in source.getFeatures()]
+        x_var = vector.convert_nulls([i[namefieldname] for i in source.getFeatures(QgsFeatureRequest().setFlags(QgsFeatureRequest.NoGeometry))], '<NULL>')
 
         data = [go.Bar(x=x_var,
                        y=values[valuefieldname])]

python/plugins/processing/algs/qgis/BoxPlot.py

@@ -96,7 +96,7 @@ def processAlgorithm(self, parameters, context, feedback):
         values = vector.values(source, valuefieldname)
 
         x_index = source.fields().lookupField(namefieldname)
-        x_var = [i[namefieldname] for i in source.getFeatures(QgsFeatureRequest().setFlags(QgsFeatureRequest.NoGeometry).setSubsetOfAttributes([x_index]))]
+        x_var = vector.convert_nulls([i[namefieldname] for i in source.getFeatures(QgsFeatureRequest().setFlags(QgsFeatureRequest.NoGeometry).setSubsetOfAttributes([x_index]))], '<NULL>')
 
         msdIndex = self.parameterAsEnum(parameters, self.MSD, context)
         msd = True

python/plugins/processing/tests/ToolsTest.py

@@ -28,7 +28,7 @@
 import os
 import shutil
 
-from qgis.core import QgsVectorLayer
+from qgis.core import NULL, QgsVectorLayer
 from qgis.testing import start_app, unittest
 
 from processing.tests.TestData import points
@@ -77,6 +77,17 @@ def testValues(self):
         self.assertEqual(res['id'], [1, 2, 3, 4, 5, 6, 7, 8, 9])
         self.assertEqual(res[2], [2, 1, 0, 2, 1, 0, 0, 0, 0])
 
+    def testConvertNulls(self):
+        self.assertEqual(vector.convert_nulls([]), [])
+        self.assertEqual(vector.convert_nulls([], '_'), [])
+        self.assertEqual(vector.convert_nulls([NULL]), [None])
+        self.assertEqual(vector.convert_nulls([NULL], '_'), ['_'])
+        self.assertEqual(vector.convert_nulls([NULL], -1), [-1])
+        self.assertEqual(vector.convert_nulls([1, 2, 3]), [1, 2, 3])
+        self.assertEqual(vector.convert_nulls([1, None, 3]), [1, None, 3])
+        self.assertEqual(vector.convert_nulls([1, NULL, 3, NULL]), [1, None, 3, None])
+        self.assertEqual(vector.convert_nulls([1, NULL, 3, NULL], '_'), [1, '_', 3, '_'])
+
 
 if __name__ == '__main__':
     unittest.main()

python/plugins/processing/tools/vector.py

@@ -25,9 +25,7 @@
 
 __revision__ = '$Format:%H$'
 
-import csv
-
-from qgis.core import (QgsWkbTypes,
+from qgis.core import (NULL,
                        QgsFeatureRequest)
 
 
@@ -90,6 +88,16 @@ def values(source, *attributes):
     return ret
 
 
+def convert_nulls(values, replacement=None):
+    """
+    Converts NULL items in a list of values to a replacement value (usually None)
+    :param values: list of values
+    :param replacement: value to use in place of NULL
+    :return: converted list
+    """
+    return [i if i != NULL else replacement for i in values]
+
+
 def checkMinDistance(point, index, distance, points):
     """Check if distance from given point to all other points is greater
     than given value.