[processing][needs-docs] Resurrect ability to convert models to scripts

Brings back QGIS 2.18's ability to directly convert a Processing model
to an equivalent Processing Python script algorithm, correctly
updated and working in the 3.x API.

Available from the model dialog, and from the right-click context
menu on an existing model.

Sponsored by Solspec

python/plugins/processing/modeler/ExportModelAsPythonScriptAction.py

@@ -0,0 +1,51 @@
+# -*- coding: utf-8 -*-
+
+"""
+***************************************************************************
+    EditModelAction.py
+    ---------------------
+    Date                 : February 2019
+    Copyright            : (C) 2019 by Nyall Dawson
+    Email                : nyall dot dawson at gmail dot com
+***************************************************************************
+*                                                                         *
+*   This program is free software; you can redistribute it and/or modify  *
+*   it under the terms of the GNU General Public License as published by  *
+*   the Free Software Foundation; either version 2 of the License, or     *
+*   (at your option) any later version.                                   *
+*                                                                         *
+***************************************************************************
+"""
+
+__author__ = 'Nyall Dawson'
+__date__ = 'February 2019'
+__copyright__ = '(C) 2019, Nyall Dawson'
+
+# This will get replaced with a git SHA1 when you do a git archive
+
+__revision__ = '$Format:%H$'
+
+from qgis.PyQt.QtCore import QCoreApplication
+from qgis.core import QgsProcessingModelAlgorithm, QgsProcessing, QgsApplication
+from processing.gui.ContextAction import ContextAction
+from processing.script.ScriptEditorDialog import ScriptEditorDialog
+
+
+class ExportModelAsPythonScriptAction(ContextAction):
+
+    def __init__(self):
+        super().__init__()
+        self.name = QCoreApplication.translate('ExportModelAsPythonScriptAction', 'Export Model as Python Algorithm…')
+
+    def isEnabled(self):
+        return isinstance(self.itemData, QgsProcessingModelAlgorithm)
+
+    def icon(self):
+        return QgsApplication.getThemeIcon('/mActionSaveAsPython.svg')
+
+    def execute(self):
+        alg = self.itemData
+        dlg = ScriptEditorDialog(None)
+
+        dlg.editor.setText('\n'.join(alg.asPythonCode(QgsProcessing.PythonQgsProcessingAlgorithmSubclass, 4)))
+        dlg.show()

python/plugins/processing/modeler/ModelerAlgorithmProvider.py

@@ -47,6 +47,7 @@ from processing.modeler.AddModelFromFileAction import AddModelFromFileAction
 from processing.modeler.CreateNewModelAction import CreateNewModelAction
 from processing.modeler.DeleteModelAction import DeleteModelAction
 from processing.modeler.EditModelAction import EditModelAction
+from processing.modeler.ExportModelAsPythonScriptAction import ExportModelAsPythonScriptAction
 from processing.modeler.OpenModelFromFileAction import OpenModelFromFileAction
 from processing.modeler.exceptions import WrongModelException
 from processing.modeler.ModelerUtils import ModelerUtils
@@ -59,7 +60,9 @@ class ModelerAlgorithmProvider(QgsProcessingProvider):
     def __init__(self):
         super().__init__()
         self.actions = [CreateNewModelAction(), OpenModelFromFileAction(), AddModelFromFileAction()]
-        self.contextMenuActions = [EditModelAction(), DeleteModelAction()]
+        sep_action = ContextAction()
+        sep_action.is_separator = True
+        self.contextMenuActions = [EditModelAction(), DeleteModelAction(), sep_action, ExportModelAsPythonScriptAction()]
         self.algs = []
         self.isLoading = False
 

python/plugins/processing/modeler/ModelerDialog.py

@@ -61,7 +61,9 @@ from qgis.PyQt.QtWidgets import (QGraphicsView,
                                  QVBoxLayout,
                                  QGridLayout,
                                  QFrame,
-                                 QLineEdit)
+                                 QLineEdit,
+                                 QToolButton,
+                                 QAction)
 from qgis.PyQt.QtGui import (QIcon,
                              QImage,
                              QPainter,
@@ -70,7 +72,7 @@ from qgis.PyQt.QtSvg import QSvgGenerator
 from qgis.PyQt.QtPrintSupport import QPrinter
 from qgis.core import (Qgis,
                        QgsApplication,
-                       QgsProcessingAlgorithm,
+                       QgsProcessing,
                        QgsProject,
                        QgsSettings,
                        QgsMessageLog,
@@ -92,6 +94,7 @@ from processing.modeler.ModelerParametersDialog import ModelerParametersDialog
 from processing.modeler.ModelerUtils import ModelerUtils
 from processing.modeler.ModelerScene import ModelerScene
 from processing.modeler.ProjectProvider import PROJECT_PROVIDER_ID
+from processing.script.ScriptEditorDialog import ScriptEditorDialog
 from qgis.utils import iface
 
 
@@ -253,6 +256,13 @@ class ModelerDialog(BASE, WIDGET):
             self.mToolbar.setIconSize(iface.iconSize())
             self.setStyleSheet(iface.mainWindow().styleSheet())
 
+        self.toolbutton_export_to_script = QToolButton()
+        self.toolbutton_export_to_script.setPopupMode(QToolButton.InstantPopup)
+        self.export_to_script_algorithm_action = QAction(self.tr('Export as Script Algorithm…'))
+        self.toolbutton_export_to_script.addActions([self.export_to_script_algorithm_action])
+        self.mToolbar.insertWidget(self.mActionExportImage, self.toolbutton_export_to_script)
+        self.export_to_script_algorithm_action.triggered.connect(self.export_as_script_algorithm)
+
         self.mActionOpen.setIcon(
             QgsApplication.getThemeIcon('/mActionFileOpen.svg'))
         self.mActionSave.setIcon(
@@ -275,8 +285,8 @@ class ModelerDialog(BASE, WIDGET):
             QgsApplication.getThemeIcon('/mActionSaveAsPDF.svg'))
         self.mActionExportSvg.setIcon(
             QgsApplication.getThemeIcon('/mActionSaveAsSVG.svg'))
-        #self.mActionExportPython.setIcon(
-        #    QgsApplication.getThemeIcon('/mActionSaveAsPython.svg'))
+        self.toolbutton_export_to_script.setIcon(
+            QgsApplication.getThemeIcon('/mActionSaveAsPython.svg'))
         self.mActionEditHelp.setIcon(
             QgsApplication.getThemeIcon('/mActionEditHelpContent.svg'))
         self.mActionRun.setIcon(
@@ -814,3 +824,9 @@ class ModelerDialog(BASE, WIDGET):
             newX = MARGIN + BOX_WIDTH / 2
             newY = MARGIN * 2 + BOX_HEIGHT + BOX_HEIGHT / 2
         return QPointF(newX, newY)
+
+    def export_as_script_algorithm(self):
+        dlg = ScriptEditorDialog(None)
+
+        dlg.editor.setText('\n'.join(self.model.asPythonCode(QgsProcessing.PythonQgsProcessingAlgorithmSubclass, 4)))
+        dlg.show()

python/plugins/processing/ui/DlgModeler.ui

@@ -166,10 +166,10 @@
   </action>
   <action name="mActionExportPython">
    <property name="text">
-    <string>Export as Python script…</string>
+    <string>Export as Python Script…</string>
    </property>
    <property name="toolTip">
-    <string>Export as Python script</string>
+    <string>Export as Python Script</string>
    </property>
   </action>
   <action name="mActionEditHelp">