New rule 006_0001_no_default_value from Rick

[xiwenc]

5. Custom rule (default values on attributes) I created a custom rule to discourage default values on attributes and it appears to work well. I’m sharing it below in case it’s useful for you or the community. See the attached files for the rule.

006_0001_no_default_value_test.yaml

006_0001_no_default_value.rego.txt

[bartzantingh]

I have a couple of remarks:

You can use the some...in function to iterate over the input file's entities and immediately assign a value to the entity variable. The same goes for the attributes within an entity. Also, the object.get() function is pretty expensive, and there is no need to use it anyway. Because there always is just one Value and one DefaultValue in an attribute, you can just pass it directly to the helper function by using default_value_is_set(attribute.Value.DefaultValue).

This results in a lot less code and a more efficient rule.

Consider changing

some entity_index
some attribute_index

entity := input.Entities[entity_index]
attribute := entity.Attributes[attribute_index]

# In the DomainModel yaml, DefaultValue is nested under Value
stored_value := object.get(attribute, "Value", {})
default_value := object.get(stored_value, "DefaultValue", null)

default_value_is_set(default_value)

to

some entity in input.Entities
some attribute in entity.Attributes

default_value_is_set(attribute.Value.DefaultValue)

Other comments

• I think the rule number should start with 002, as that is the folder where all the rules for the domain model are located in
• Add double quotes to the rule number in the annotations; else it will not be displayed correctly in the linting results. See Rule numbers of Rego rules not showing correctly in lint result error texts #17
• Using two separate functions for checking the value seems a bit excessive, could be combined into two checks (!= null and != "") in one function
• Clean code: consider renaming default_value_is_set to is_default_value_set or has_default_value, so it reads more like a sentence that can be answered with yes or no
• Add author name to annotations
• The test file doesn't seem to work, as the rule is not imported. Also consider rewriting it in Rego instead of YAML

[xiwenc]

Thanks for the feedback Bart! This rule input was shared directly with me via email. It was added here so that it can be picked up by others (or myself when i have time)

Related to this and perhaps with what you are doing we are considering to drop Rego from mxlint: mxlint/mxlint-cli#94