Unable to run v.clean in QGIS 3.0.1 in Python console

Question

I am trying to use v.clean algorithm in QGIS 3 python console. Code is as follows.

    lyr = iface.activeLayer()
    new_layer = lyr.materialize(QgsFeatureRequest().setFilterFids(lyr.selectedFeatureIds()))
    QgsProject.instance().addMapLayer(new_layer)

    alg = 'grass7:v.clean'

    extent = new_layer.extent()
    xmin = extent.xMinimum()
    xmax = extent.xMaximum()
    ymin = extent.yMinimum()
    ymax = extent.yMaximum()

    params = {"input": new_layer, "type": 1, "tool": 0, "-b": True, "-c": True,
              "output": "E:/out.shp", "error": "E:/errLayer.shp",
              "GRASS_REGION_PARAMETER": "%f,%f,%f,%f" % (xmin, xmax, ymin, ymax),
              "GRASS_SNAP_TOLERANCE_PARAMETER": 5, "GRASS_MIN_AREA_PARAMETER": 5,
              "GRASS_OUTPUT_TYPE_PARAMETER": 2}

    test = processing.run(alg, params)

When I run this code I get following error:

    Traceback (most recent call last):
    File "C:\PROGRA~1\QGIS3~1.0\apps\qgis\python\plugins\splitroads\Split_Roads.py", line 211, in run
    test = processing.run(alg, params)
    File "C:\PROGRA~1\QGIS3~1.0\apps\qgis\python\plugins\processing\tools\general.py", line 84, in run
    return Processing.runAlgorithm(algOrName, parameters, onFinish, feedback, context)
    File "C:\PROGRA~1\QGIS3~1.0\apps\qgis\python\plugins\processing\core\Processing.py", line 189, in runAlgorithm
    feedback.reportError(msg)
    TypeError: reportError() missing 1 required positional argument: 'fatal_error'

I have also checked input parameters of v.clean algorithm by using

   processing.algorithmHelp("grass7:v.clean")

and got following output

   Input parameters:

   input:  <QgsProcessingParameterVectorLayer>
           Layer to clean
   type:  <QgsProcessingParameterEnum>
          Input feature type
          0 - point
          1 - line
          2 - boundary
          3 - centroid
          4 - area
          5 - face
          6 - kernel
    tool: <QgsProcessingParameterEnum>
          Cleaning tool
          0 - break
          1 - snap
          2 - rmdangle
          3 - chdangle
          4 - rmbridge
          5 - chbridge
          6 - rmdupl
          7 - rmdac
          8 - bpol
          9 - prune
          10 - rmarea
          11 - rmline
          12 - rmsa
   threshold: <QgsProcessingParameterString>
              Threshold (comma separated for each tool)
   -b:  <QgsProcessingParameterBoolean>
        Do not build topology for the output vector
   -c:  <QgsProcessingParameterBoolean>
        Combine tools with recommended follow-up tools
   output:  <QgsProcessingParameterVectorDestination>
            Cleaned
   error:  <QgsProcessingParameterVectorDestination>
    Errors
   GRASS_REGION_PARAMETER:  <QgsProcessingParameterExtent>
    GRASS GIS 7 region extent
   GRASS_SNAP_TOLERANCE_PARAMETER:  <QgsProcessingParameterNumber>
    v.in.ogr snap tolerance (-1 = no snap)
   GRASS_MIN_AREA_PARAMETER:  <QgsProcessingParameterNumber>
    v.in.ogr min area
   GRASS_OUTPUT_TYPE_PARAMETER:  <QgsProcessingParameterEnum>
   v.out.ogr output type
    0 - auto
    1 - point
    2 - line
    3 - area

   Outputs:

   output:  <QgsProcessingOutputVectorLayer>
     Cleaned
   error:  <QgsProcessingOutputVectorLayer>
     Errors

Everything seems fine but I am unable to run it.Can you please let me know how to run v.clean successfully in python console using QGIS 3?

Answer 1

It appears that it was due to some bug I updated to latest version 3.0.2 of QGIS and modified processing.py to import QgsProcessingFeedback as follows

from qgis.core import (QgsMessageLog,
                   QgsApplication,
                   QgsMapLayer,
                   QgsProcessingProvider,
                   QgsProcessingAlgorithm,
                   QgsProcessingException,
                   QgsProcessingParameterDefinition,
                   QgsProcessingOutputVectorLayer,
                   QgsProcessingOutputRasterLayer,
                   QgsProcessingOutputMapLayer,
                   QgsProcessingOutputMultipleLayers,
                   QgsProcessingFeedback)

and everything is working fine now.