Move execution check to QgsProcessingAlgorithm

qgis · Jun 5, 2017 · fac8ca4 · fac8ca4
1 parent 03e40f7
commit fac8ca4
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Showing 9 changed files with 34 additions and 24 deletions.
diff --git a/python/core/processing/qgsprocessingalgorithm.sip b/python/core/processing/qgsprocessingalgorithm.sip
@@ -104,6 +104,15 @@ class QgsProcessingAlgorithm
  :rtype: Flags
 %End
 
+    virtual bool canExecute( QString *errorMessage /Out/ = 0 ) const;
+%Docstring
+ Returns true if the algorithm can execute. Algorithm subclasses can return false
+ here to indicate that they are not able to execute, e.g. as a result of unmet
+ external dependencies. If specified, the ``errorMessage`` argument will be filled
+ with a localised error message describing why the algorithm cannot execute.
+ :rtype: bool
+%End
+
     QgsProcessingProvider *provider() const;
 %Docstring
  Returns the provider to which this algorithm belongs.

diff --git a/python/plugins/processing/algs/grass7/Grass7Algorithm.py b/python/plugins/processing/algs/grass7/Grass7Algorithm.py
@@ -572,8 +572,9 @@ def exportRasterLayer(self, layer):
     def getTempFilename(self):
         return system.getTempFilename()
 
-    def checkBeforeOpeningParametersDialog(self):
-        return Grass7Utils.checkGrass7IsInstalled()
+    def canExecute(self):
+        message = Grass7Utils.checkGrass7IsInstalled()
+        return not message, message
 
     def checkParameterValuesBeforeExecuting(self):
         if self.module:

diff --git a/python/plugins/processing/core/GeoAlgorithm.py b/python/plugins/processing/core/GeoAlgorithm.py
@@ -130,20 +130,6 @@ def getParameterDescriptions(self):
         descs = {}
         return descs
 
-    def checkBeforeOpeningParametersDialog(self):
-        """If there is any check to perform before the parameters
-        dialog is opened, it should be done here.
-
-        This method returns an error message string if there is any
-        problem (for instance, an external app not configured yet),
-        or None if the parameters dialog can be opened.
-
-        Note that this check should also be done in the
-        processAlgorithm method, since algorithms can be called without
-        opening the parameters dialog.
-        """
-        return None
-
     def checkParameterValuesBeforeExecuting(self):
         """If there is any check to do before launching the execution
         of the algorithm, it should be done here.

diff --git a/python/plugins/processing/gui/ProcessingToolbox.py b/python/plugins/processing/gui/ProcessingToolbox.py
@@ -255,8 +255,8 @@ def executeAlgorithm(self):
         if isinstance(item, TreeAlgorithmItem):
             context = dataobjects.createContext()
             alg = QgsApplication.processingRegistry().algorithmById(item.alg.id())
-            message = alg.checkBeforeOpeningParametersDialog()
-            if message:
+            ok, message = alg.canExecute()
+            if not ok:
                 dlg = MessageDialog()
                 dlg.setTitle(self.tr('Error executing algorithm'))
                 dlg.setMessage(

diff --git a/python/plugins/processing/gui/menus.py b/python/plugins/processing/gui/menus.py
@@ -193,8 +193,8 @@ def removeAlgorithmEntry(alg, menuName, submenuName, actionText=None, delButton=
 
 
 def _executeAlgorithm(alg):
-    message = alg.checkBeforeOpeningParametersDialog()
-    if message:
+    ok, message = alg.canExecute()
+    if not ok:
         dlg = MessageDialog()
         dlg.setTitle(Processing.tr('Missing dependency'))
         dlg.setMessage(

diff --git a/python/plugins/processing/modeler/ModelerAlgorithm.py b/python/plugins/processing/modeler/ModelerAlgorithm.py
@@ -525,11 +525,12 @@ def getAsCommand(self):
         else:
             return None
 
-    def checkBeforeOpeningParametersDialog(self):
+    def canExecute(self):
         for alg in list(self.algs.values()):
             algInstance = QgsApplication.processingRegistry().algorithmById(alg.consoleName)
             if algInstance is None:
-                return self.tr("The model you are trying to run contains an algorithm that is not available: <i>{0}</i>").format(alg.consoleName)
+                return False, self.tr("The model you are trying to run contains an algorithm that is not available: <i>{0}</i>").format(alg.consoleName)
+        return True, None
 
     def setModelerView(self, dialog):
         self.modelerdialog = dialog

diff --git a/python/plugins/processing/script/ScriptAlgorithm.py b/python/plugins/processing/script/ScriptAlgorithm.py
@@ -122,8 +122,8 @@ def defineCharacteristicsFromScript(self):
                 except:
                     pass
 
-    def checkBeforeOpeningParametersDialog(self):
-        return self.error
+    def canExecute(self):
+        return not self.error, self.error
 
     def checkInputCRS(self):
         if self.noCRSWarning:

diff --git a/src/core/processing/qgsprocessingalgorithm.cpp b/src/core/processing/qgsprocessingalgorithm.cpp
@@ -49,6 +49,11 @@ QgsProcessingAlgorithm::Flags QgsProcessingAlgorithm::flags() const
   return FlagSupportsBatch;
 }
 
+bool QgsProcessingAlgorithm::canExecute( QString * ) const
+{
+  return true;
+}
+
 QgsProcessingProvider *QgsProcessingAlgorithm::provider() const
 {
   return mProvider;

diff --git a/src/core/processing/qgsprocessingalgorithm.h b/src/core/processing/qgsprocessingalgorithm.h
@@ -117,6 +117,14 @@ class CORE_EXPORT QgsProcessingAlgorithm
      */
     virtual Flags flags() const;
 
+    /**
+     * Returns true if the algorithm can execute. Algorithm subclasses can return false
+     * here to indicate that they are not able to execute, e.g. as a result of unmet
+     * external dependencies. If specified, the \a errorMessage argument will be filled
+     * with a localised error message describing why the algorithm cannot execute.
+     */
+    virtual bool canExecute( QString *errorMessage SIP_OUT = nullptr ) const;
+
     /**
      * Returns the provider to which this algorithm belongs.
      */