Parameter validation via plugin (#4958)

* Expose part parameter validation to plugins

- Allow ValidationMixin plugins to validate part parameter values

* Update sample plugin

* Catch and re-throw error

* Update docs

* Improve plugin docs

* Simplify validation sample

* Calculate numeric value first

InvenTree/part/models.py

@@ -572,7 +572,7 @@ class Part(InvenTreeBarcodeMixin, InvenTreeNotesMixin, MetadataMixin, MPTTModel)
         """Ensure that the IPN (internal part number) is valid for this Part"
 
         - Validation is handled by custom plugins
-        - By default, no validation checks are perfomed
+        - By default, no validation checks are performed
         """
 
         from plugin.registry import registry
@@ -3505,6 +3505,24 @@ class PartParameter(MetadataMixin, models.Model):
                     'data': _('Invalid choice for parameter value')
                 })
 
+        self.calculate_numeric_value()
+
+        # Run custom validation checks (via plugins)
+        from plugin.registry import registry
+
+        for plugin in registry.with_mixin('validation'):
+
+            # Note: The validate_part_parameter function may raise a ValidationError
+            try:
+                result = plugin.validate_part_parameter(self, self.data)
+                if result:
+                    break
+            except ValidationError as exc:
+                # Re-throw the ValidationError against the 'data' field
+                raise ValidationError({
+                    'data': exc.message
+                })
+
     def calculate_numeric_value(self):
         """Calculate a numeric value for the parameter data.
 

InvenTree/plugin/base/integration/mixins.py

@@ -21,6 +21,7 @@ class ValidationMixin:
 
     - Part names
     - Part IPN (internal part number) values
+    - Part parameter values
     - Serial numbers
     - Batch codes
 
@@ -150,6 +151,21 @@ class ValidationMixin:
         """
         return None
 
+    def validate_part_parameter(self, parameter, data):
+        """Validate a parameter value.
+
+        Arguments:
+            parameter: The parameter we are validating
+            data: The proposed parameter value
+
+        Returns:
+            None or True (refer to class docstring)
+
+        Raises:
+            ValidationError if the proposed parameter value is objectionable
+        """
+        pass
+
 
 class NavigationMixin:
     """Mixin that enables custom navigation links with the plugin."""

InvenTree/plugin/samples/integration/validation_sample.py

@@ -18,7 +18,7 @@ class CustomValidationMixin(SettingsMixin, ValidationMixin, InvenTreePlugin):
     SLUG = "validator"
     TITLE = "Custom Validator Plugin"
     DESCRIPTION = "A sample plugin for demonstrating custom validation functionality"
-    VERSION = "0.2"
+    VERSION = "0.3.0"
 
     SETTINGS = {
         'ILLEGAL_PART_CHARS': {
@@ -78,6 +78,17 @@ class CustomValidationMixin(SettingsMixin, ValidationMixin, InvenTreePlugin):
         if self.get_setting('IPN_MUST_CONTAIN_Q') and 'Q' not in ipn:
             raise ValidationError("IPN must contain 'Q'")
 
+    def validate_part_parameter(self, parameter, data):
+        """Validate part parameter data.
+
+        These examples are silly, but serve to demonstrate how the feature could be used
+        """
+
+        if parameter.template.name.lower() in ['length', 'width']:
+            d = int(data)
+            if d >= 100:
+                raise ValidationError("Value must be less than 100")
+
     def validate_serial_number(self, serial: str, part):
         """Validate serial number for a given StockItem