Fix upgrading custom FDM printers from 2.5

CURA-4188

Custom FDM printers in 2.5 don't have multi-extrusion support but they
do since 2.6. Upgrading from 2.5 to 2.6 will not create the missing
extruder stacks for the old custom FDM printers, which causes a crash.
This fix makes sure that all custom FDM printers will have 8 extruder
stacks during the upgrade so that Cura can still start normally and
those printers will still be usable.

plugins/VersionUpgrade/VersionUpgrade25to26/VersionUpgrade25to26.py

@@ -3,9 +3,14 @@
 
 import configparser #To parse the files we need to upgrade and write the new files.
 import io #To serialise configparser output to a string.
+import os
+from urllib.parse import quote_plus
 
+from UM.Resources import Resources
 from UM.VersionUpgrade import VersionUpgrade
 
+from cura.CuraApplication import CuraApplication
+
 _removed_settings = { #Settings that were removed in 2.5.
     "start_layers_at_same_position",
     "sub_div_rad_mult"
@@ -20,6 +25,11 @@ _split_settings = { #These settings should be copied to all settings it was spli
 #
 #   All of these methods are essentially stateless.
 class VersionUpgrade25to26(VersionUpgrade):
+
+    def __init__(self):
+        super().__init__()
+        self._current_fdm_printer_count = 2
+
     ##  Gets the version number from a CFG file in Uranium's 2.5 format.
     #
     #   Since the format may change, this is implemented for the 2.5 format only
@@ -103,3 +113,145 @@ class VersionUpgrade25to26(VersionUpgrade):
         output = io.StringIO()
         parser.write(output)
         return [filename], [output.getvalue()]
+
+    def upgradeMachineStack(self, serialised, filename):
+        parser = configparser.ConfigParser(interpolation=None)
+        parser.read_string(serialised)
+
+        # NOTE: This is for Custom FDM printers
+        # In 2.5, Custom FDM printers don't support multiple extruders, but since 2.6 they do.
+        machine_id = parser["general"]["id"]
+        quality_container_id = parser["containers"]["2"]
+        material_container_id = parser["containers"]["3"]
+        definition_container_id = parser["containers"]["6"]
+
+        if definition_container_id == "custom" and not self._checkCustomFdmPrinterHasExtruderStack(machine_id):
+            # go through all extruders and make sure that this custom FDM printer has 8 extruder stacks.
+            self._getNextUniqueCustomFdmPrinterExtruderStackIdIndex()
+            for position in range(8):
+                self._createCustomFdmPrinterExtruderStack(machine_id, position, quality_container_id, material_container_id)
+
+        # Update version numbers
+        parser["general"]["version"] = "3"
+        parser["metadata"]["setting_version"] = "1"
+
+        # Re-serialise the file.
+        output = io.StringIO()
+        parser.write(output)
+
+        return [filename], [output.getvalue()]
+
+    def _getNextUniqueCustomFdmPrinterExtruderStackIdIndex(self):
+        extruder_stack_dir = Resources.getPath(CuraApplication.ResourceTypes.ExtruderStack)
+        file_name_list = os.listdir(extruder_stack_dir)
+        file_name_list = [os.path.basename(file_name) for file_name in file_name_list]
+        while True:
+            self._current_fdm_printer_count += 1
+            stack_id_exists = False
+            for position in range(8):
+                stack_id = "custom_extruder_%s" % (position + 1)
+                if self._current_fdm_printer_count > 1:
+                    stack_id += " #%s" % self._current_fdm_printer_count
+
+                if stack_id in file_name_list:
+                    stack_id_exists = True
+                    break
+            if not stack_id_exists:
+                break
+
+        return self._current_fdm_printer_count
+
+    def _checkCustomFdmPrinterHasExtruderStack(self, machine_id):
+        # go through all extruders and make sure that this custom FDM printer has extruder stacks.
+        extruder_stack_dir = Resources.getPath(CuraApplication.ResourceTypes.ExtruderStack)
+        has_extruders = False
+        for item in os.listdir(extruder_stack_dir):
+            file_path = os.path.join(extruder_stack_dir, item)
+            if not os.path.isfile(file_path):
+                continue
+
+            parser = configparser.ConfigParser()
+            try:
+                parser.read([file_path])
+            except:
+                # skip, it is not a valid stack file
+                continue
+
+            if "metadata" not in parser:
+                continue
+            if "machine" not in parser["metadata"]:
+                continue
+
+            if machine_id != parser["metadata"]["machine"]:
+                continue
+            has_extruders = True
+
+        return has_extruders
+
+    def _createCustomFdmPrinterExtruderStack(self, machine_id: str, position: int, quality_id: str, material_id: str):
+        stack_id = "custom_extruder_%s" % (position + 1)
+        if self._current_fdm_printer_count > 1:
+            stack_id += " #%s" % self._current_fdm_printer_count
+
+        definition_id = "custom_extruder_%s" % (position + 1)
+
+        # create a definition changes container for this stack
+        definition_changes_parser = self._getCustomFdmPrinterDefinitionChanges(stack_id)
+        definition_changes_id = definition_changes_parser["general"]["name"]
+
+        parser = configparser.ConfigParser()
+        parser.add_section("general")
+        parser["general"]["version"] = str(2)
+        parser["general"]["name"] = "Extruder %s" % (position + 1)
+        parser["general"]["id"] = stack_id
+
+        parser.add_section("metadata")
+        parser["metadata"]["type"] = "extruder_train"
+        parser["metadata"]["machine"] = machine_id
+        parser["metadata"]["position"] = str(position)
+
+        parser.add_section("containers")
+        parser["containers"]["0"] = "empty"
+        parser["containers"]["1"] = "empty_quality_changes"
+        parser["containers"]["2"] = quality_id
+        parser["containers"]["3"] = material_id
+        parser["containers"]["4"] = "empty_variant"
+        parser["containers"]["5"] = definition_changes_id
+        parser["containers"]["6"] = definition_id
+
+        definition_changes_output = io.StringIO()
+        definition_changes_parser.write(definition_changes_output)
+        definition_changes_filename = quote_plus(definition_changes_id) + ".inst.cfg"
+
+        extruder_output = io.StringIO()
+        parser.write(extruder_output)
+        extruder_filename = quote_plus(stack_id) + ".extruder.cfg"
+
+        extruder_stack_dir = Resources.getPath(CuraApplication.ResourceTypes.ExtruderStack)
+        definition_changes_dir = Resources.getPath(CuraApplication.ResourceTypes.DefinitionChangesContainer)
+
+        with open(os.path.join(definition_changes_dir, definition_changes_filename), "w") as f:
+            f.write(definition_changes_output.getvalue())
+        with open(os.path.join(extruder_stack_dir, extruder_filename), "w") as f:
+            f.write(extruder_output.getvalue())
+
+    ##  Creates a definition changes container which doesn't contain anything for the Custom FDM Printers.
+    #   The container ID will be automatically generated according to the given stack name.
+    def _getCustomFdmPrinterDefinitionChanges(self, stack_id: str):
+        # In 2.5, there is no definition_changes container for the Custom FDM printer, so it should be safe to use the
+        # default name unless some one names the printer as something like "Custom FDM Printer_settings".
+        definition_changes_id = stack_id + "_settings"
+
+        parser = configparser.ConfigParser()
+        parser.add_section("general")
+        parser["general"]["version"] = str(2)
+        parser["general"]["name"] = definition_changes_id
+        parser["general"]["definition"] = "custom"
+
+        parser.add_section("metadata")
+        parser["metadata"]["type"] = "definition_changes"
+        parser["metadata"]["setting_version"] = str(1)
+
+        parser.add_section("values")
+
+        return parser