support grass algorithms in profile folder

python/plugins/grassprovider/Grass7Algorithm.py

@@ -25,6 +25,7 @@
 import uuid
 import math
 import importlib
+from pathlib import Path
 
 from qgis.PyQt.QtCore import QCoreApplication, QUrl
 
@@ -139,11 +140,17 @@ def __init__(self, descriptionfile):
 
         # Use the ext mechanism
         name = self.name().replace('.', '_')
+        self.module = None
         try:
-            self.module = importlib.import_module(
-                'grassprovider.ext.{}'.format(name))
-        except ImportError:
-            self.module = None
+            extpath = self.descriptionFile.parents[1].joinpath('ext', name + '.py')
+            # this check makes it a bit faster
+            if extpath.exists():
+                spec = importlib.util.spec_from_file_location('grassprovider.ext.' + name, extpath)
+                self.module = importlib.util.module_from_spec(spec)
+                spec.loader.exec_module(self.module)
+        except Exception as e:
+            QgsMessageLog.logMessage(self.tr('Failed to load: {0}\n{1}').format(extpath, e), 'Processing', Qgis.Critical)
+            pass
 
     def createInstance(self):
         return self.__class__(self.descriptionFile)
@@ -200,7 +207,7 @@ def defineCharacteristicsFromFile(self):
         """
         Create algorithm parameters and outputs from a text file.
         """
-        with open(self.descriptionFile) as lines:
+        with self.descriptionFile.open() as lines:
             # First line of the file is the Grass algorithm name
             line = lines.readline().strip('\n').strip()
             self.grass7Name = line

python/plugins/grassprovider/Grass7AlgorithmProvider.py

@@ -20,6 +20,7 @@
 __copyright__ = '(C) 2014, Victor Olaya'
 
 import os
+from pathlib import Path
 from qgis.PyQt.QtCore import QCoreApplication
 from qgis.core import (Qgis,
                        QgsApplication,
@@ -35,7 +36,7 @@
 
 
 class Grass7AlgorithmProvider(QgsProcessingProvider):
-    descriptionFolder = Grass7Utils.grassDescriptionPath()
+    descriptionFolders = Grass7Utils.grassDescriptionFolders()
 
     def __init__(self):
         super().__init__()
@@ -86,18 +87,18 @@ def unload(self):
 
     def createAlgsList(self):
         algs = []
-        folder = self.descriptionFolder
-        for descriptionFile in os.listdir(folder):
-            if descriptionFile.endswith('txt'):
+        folders = self.descriptionFolders
+        for folder in folders:
+            for descriptionFile in folder.glob('*.txt'):
                 try:
-                    alg = Grass7Algorithm(os.path.join(folder, descriptionFile))
+                    alg = Grass7Algorithm(descriptionFile)
                     if alg.name().strip() != '':
                         algs.append(alg)
                     else:
                         QgsMessageLog.logMessage(self.tr('Could not open GRASS GIS 7 algorithm: {0}').format(descriptionFile), self.tr('Processing'), Qgis.Critical)
                 except Exception as e:
                     QgsMessageLog.logMessage(
-                        self.tr('Could not open GRASS GIS 7 algorithm: {0}\n{1}').format(descriptionFile, str(e)), self.tr('Processing'), Qgis.Critical)
+                        self.tr('Could not open GRASS GIS 7 algorithm: {0}\n{1}').format(descriptionFile, e), self.tr('Processing'), Qgis.Critical)
         return algs
 
     def loadAlgorithms(self):

python/plugins/grassprovider/Grass7Utils.py

@@ -25,6 +25,7 @@
 import subprocess
 import os
 import sys
+from pathlib import Path
 
 from qgis.core import (Qgis,
                        QgsApplication,
@@ -254,8 +255,23 @@ def grassPath():
         return folder or ''
 
     @staticmethod
-    def grassDescriptionPath():
-        return os.path.join(os.path.dirname(__file__), 'description')
+    def userDescriptionFolder():
+        """
+        Creates and returns a directory for users to create additional algorithm descriptions.
+        Or modified versions of stock algorithm descriptions shipped with QGIS.
+        """
+        folder = Path(userFolder(), 'grassaddons', 'description')
+        folder.mkdir(parents=True, exist_ok=True)
+        return folder
+
+    @staticmethod
+    def grassDescriptionFolders():
+        """
+        Returns the directories to search for algorithm descriptions.
+        Note that the provider will load from these in sequence, so we put the userDescriptionFolder first
+        to allow users to create modified versions of stock algorithms shipped with QGIS.
+        """
+        return [Grass7Utils.userDescriptionFolder(), Path(__file__).parent.joinpath('description')]
 
     @staticmethod
     def getWindowsCodePage():