[Plugin] Allow custom plugins for running validation routines (#3776)

* Adds new plugin mixin for performing custom validation steps

* Adds simple test plugin for custom validation

* Run part name and IPN validators checks through loaded plugins

* Expose more validation functions to plugins:

- SalesOrder reference
- PurchaseOrder reference
- BuildOrder reference

* Remove custom validation of reference fields

- For now, this is too complex to consider given the current incrementing-reference implementation
- Might revisit this at a later stage.

* Custom validation of serial numbers:

- Replace "checkIfSerialNumberExists" method with "validate_serial_number"
- Pass serial number through to custom plugins
- General code / docstring improvements

* Update unit tests

* Update InvenTree/stock/tests.py

Co-authored-by: Matthias Mair <code@mjmair.com>

* Adds global setting to specify whether serial numbers must be unique globally

- Default is false to preserve behaviour

* Improved error message when attempting to create stock item with invalid serial numbers

* Add more detail to existing serial error message

* Add unit testing for serial number uniqueness

* Allow plugins to convert a serial number to an integer (for optimized sorting)

* Add placeholder plugin methods for incrementing and decrementing serial numbers

* Typo fix

* Add improved method for determining the "latest" serial number

* Remove calls to getLatestSerialNumber

* Update validate_serial_number method

- Add option to disable checking for duplicates
- Don't pass optional StockItem through to plugins

* Refactor serial number extraction methods

- Expose the "incrementing" portion to external plugins

* Bug fixes

* Update unit tests

* Fix for get_latest_serial_number

* Ensure custom serial integer values are clipped

* Adds a plugin for validating and generating hexadecimal serial numbers

* Update unit tests

* Add stub methods for batch code functionality

* remove "hex serials" plugin

- Was simply breaking unit tests

* Allow custom plugins to generate and validate batch codes

- Perform batch code validation when StockItem is saved
- Improve display of error message in modal forms

* Fix unit tests for stock app

* Log message if plugin has a duplicate slug

* Unit test fix

Co-authored-by: Matthias Mair <code@mjmair.com>

InvenTree/stock/models.py

@@ -180,9 +180,24 @@ class StockItemManager(TreeManager):
 def generate_batch_code():
     """Generate a default 'batch code' for a new StockItem.
 
-    This uses the value of the 'STOCK_BATCH_CODE_TEMPLATE' setting (if configured),
+    By default, this uses the value of the 'STOCK_BATCH_CODE_TEMPLATE' setting (if configured),
     which can be passed through a simple template.
+
+    Also, this function is exposed to the ValidationMixin plugin class,
+    allowing custom plugins to be used to generate new batch code values
     """
+
+    # First, check if any plugins can generate batch codes
+    from plugin.registry import registry
+
+    for plugin in registry.with_mixin('validation'):
+        batch = plugin.generate_batch_code()
+
+        if batch is not None:
+            # Return the first non-null value generated by a plugin
+            return batch
+
+    # If we get to this point, no plugin was able to generate a new batch code
     batch_template = common.models.InvenTreeSetting.get_setting('STOCK_BATCH_CODE_TEMPLATE', '')
 
     now = datetime.now()
@@ -260,15 +275,38 @@ class StockItem(InvenTreeBarcodeMixin, MetadataMixin, MPTTModel):
 
         This is used for efficient numerical sorting
         """
-        serial = getattr(self, 'serial', '')
 
-        # Default value if we cannot convert to an integer
-        serial_int = 0
+        serial = str(getattr(self, 'serial', '')).strip()
+
+        from plugin.registry import registry
+
+        # First, let any plugins convert this serial number to an integer value
+        # If a non-null value is returned (by any plugin) we will use that
+
+        serial_int = None
+
+        for plugin in registry.with_mixin('validation'):
+            serial_int = plugin.convert_serial_to_int(serial)
+
+            if serial_int is not None:
+                # Save the first returned result
+                # Ensure that it is clipped within a range allowed in the database schema
+                clip = 0x7fffffff
+
+                serial_int = abs(serial_int)
+
+                if serial_int > clip:
+                    serial_int = clip
+
+                self.serial_int = serial_int
+                return
 
-        if serial is not None:
+        # If we get to this point, none of the available plugins provided an integer value
 
-            serial = str(serial).strip()
+        # Default value if we cannot convert to an integer
+        serial_int = 0
 
+        if serial not in [None, '']:
             serial_int = extract_int(serial)
 
         self.serial_int = serial_int
@@ -408,16 +446,32 @@ class StockItem(InvenTreeBarcodeMixin, MetadataMixin, MPTTModel):
 
         # If the serial number is set, make sure it is not a duplicate
         if self.serial:
-            # Query to look for duplicate serial numbers
-            parts = PartModels.Part.objects.filter(tree_id=self.part.tree_id)
-            stock = StockItem.objects.filter(part__in=parts, serial=self.serial)
 
-            # Exclude myself from the search
-            if self.pk is not None:
-                stock = stock.exclude(pk=self.pk)
+            self.serial = str(self.serial).strip()
+
+            try:
+                self.part.validate_serial_number(self.serial, self, raise_error=True)
+            except ValidationError as exc:
+                raise ValidationError({
+                    'serial': exc.message,
+                })
 
-            if stock.exists():
-                raise ValidationError({"serial": _("StockItem with this serial number already exists")})
+    def validate_batch_code(self):
+        """Ensure that the batch code is valid for this StockItem.
+
+        - Validation is performed by custom plugins.
+        - By default, no validation checks are performed
+        """
+
+        from plugin.registry import registry
+
+        for plugin in registry.with_mixin('validation'):
+            try:
+                plugin.validate_batch_code(self.batch)
+            except ValidationError as exc:
+                raise ValidationError({
+                    'batch': exc.message
+                })
 
     def clean(self):
         """Validate the StockItem object (separate to field validation).
@@ -438,6 +492,8 @@ class StockItem(InvenTreeBarcodeMixin, MetadataMixin, MPTTModel):
         if type(self.batch) is str:
             self.batch = self.batch.strip()
 
+        self.validate_batch_code()
+
         try:
             # Trackable parts must have integer values for quantity field!
             if self.part.trackable: