DRY validators?

[JohnLyman]

Is it currently possible to make validators generic so they could be used in YAML anchors to reduce boilerplate?

For example, in this example in the docs, instead of having to reference age in the validator, could it be something like if self.name ...?

age:
    type: int
    validator: "{% if age <= 0 %}Must be positive{% endif %}"

Thanks for the great project!

[sisp]

I think you can achieve reusability of validators using Jinja macros: https://copier.readthedocs.io/en/stable/configuring/#importing-jinja-templates-and-macros See the example in this section that uses a macro for a default value. You should be able to use a macro in a similar way for a validator. WDYT?

[JohnLyman]

Thanks for pointing out macros. I could see how they could be useful.

In the case for validators, it's still a lot of boilerplate because I think you'd still have to pass the variable name to the macro?

int1:
  validator: "{% from 'positive_int.jinja' import positive_int %}{% if positive_int(int1) %} Must be positive{% endif %}"

int2:
  validator: "{% from 'positive_int.jinja' import positive_int %}{% if positive_int(int2) %}Must be positive{% endif %}"

int3:
  validator: "{% from 'positive_int.jinja' import positive_int %}{% if positive_int(int3) %}Must be positive{% endif %}"

vs.

int1: 
  validator: &positive_int "{% if self.name <= 0 %}Must be positive{% endif %}"
int2: 
  validator: *positive_int
int3:
  validator: *positive_int

Hopefully I'm not missing something obvious here :)

[sisp]

In the case for validators, it's still a lot of boilerplate because I think you'd still have to pass the variable name to the macro?

That's right. But it makes validator reuse more flexible, e.g. when you have a parametrized validator or one that needs more than just the answer to the question for which you're setting the validator. For instance:

age:
  validator: >-
    {% from 'validators.jinja' import validate_int %}
    {% if validate_int(age, min=0) %}
    Must be at least 0
    {% endif %}"

If you find the long line too verbose, you may use a multiline YAML string like this (at least it's more readable IMO):

int1:
  validator: >-
    {% from 'positive_int.jinja' import positive_int %}
    {% if positive_int(int1) %}
    Must be positive
    {% endif %}"

int2:
  validator: >-
    {% from 'positive_int.jinja' import positive_int %}
    {% if positive_int(int2) %}
    Must be positive
    {% endif %}"

int3:
  validator: >-
    {% from 'positive_int.jinja' import positive_int %}
    {% if positive_int(int3) %}
    Must be positive
    {% endif %}"

[JohnLyman]

That's a good point about using macros for parametrized validators.

I really like the simplicity and conciseness of using YAML anchors & aliases, but it seems as though it's not possible for a validator to reference itself (i.e. the key it is validating) unfortunately. I guess I'll live with the boilerplate or explore macros or custom extensions if they can help reduce it.

Thanks!