Add Custom Validation for User-Configured Templates

[davelopez]

Closes #20904

This PR adds custom validation to template variables in file source and object store templates, enforcing input constraints with clear error messages.

Features

Three validator types:

• regex: Pattern matching with optional negation
• length: String length bounds (min/max)
• range: Numeric value bounds (min/max)

Key characteristics:

• Validators are optional and can be chained
• Skip validation for empty optional fields
• Run on both frontend (immediate feedback) and backend (security)
• Provide clear, customizable error messages

Example Usage (included in lib/galaxy/files/templates/examples/production_s3fs.yml)

variables:
  bucket:
    label: Bucket Name
    type: string
    validators:
      - type: regex
        expression: '^(?!\s)(?!.*\s$).*$'
        message: "Bucket name cannot have leading or trailing whitespace"
      - type: regex
        expression: '^.*[^/]$'
        message: "Bucket name cannot end with a slash"

This prevents common configuration mistakes and improves the user experience when setting up custom storage connections.

How to test the changes?

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[jmchilton]

These don't use the pre-existing tool_util validators but the schema for declaring them looks compatible. It is intention that the schema is the same I assume? I wish that code had been reusable but if the schema is the same and there is test coverage I think this is fine to not reuse that stuff.

[davelopez]

Good point! I was not aware of the pre-existing tool_util validators, but I guess Claude tried to keep consistency with them when suggesting the schema.
I will try to reuse them, thanks for pointing it out!

[davelopez]

The existing tool_util validators are now reused. Thanks again for catching that!

[jmchilton]

It might be the case that galaxy-util is Python 3.7 compatible and galaxy-tool-util-models isn't - or you maybe need to have galaxy-util depend on galaxy-tool-util-models. Not sure but I could imagine both being a problem.

_______________ ERROR collecting galaxy/util/config_templates.py _______________
galaxy/util/config_templates.py:81: in <module>
    class BaseTemplateVariable(StrictModel):
galaxy/util/config_templates.py:85: in BaseTemplateVariable
    validators: Optional[Sequence[AnySafeValidatorModel]] = None
E   TypeError: 'ABCMeta' object is not subscriptable
________ ERROR collecting tests/util/test_config_template_validation.py ________
tests/util/test_config_template_validation.py:17: in <module>
    from galaxy.util.config_templates import (
galaxy/util/config_templates.py:81: in <module>
    class BaseTemplateVariable(StrictModel):
galaxy/util/config_templates.py:85: in BaseTemplateVariable
    validators: Optional[Sequence[AnySafeValidatorModel]] = None
E   TypeError: 'ABCMeta' object is not subscriptable
________ ERROR collecting tests/util/test_config_template_validation.py ________
tests/util/test_config_template_validation.py:17: in <module>
    from galaxy.util.config_templates import (
galaxy/util/config_templates.py:81: in <module>
    class BaseTemplateVariable(StrictModel):
galaxy/util/config_templates.py:85: in BaseTemplateVariable
    validators: Optional[Sequence[AnySafeValidatorModel]] = None
E   TypeError: 'ABCMeta' object is not subscriptable

[davelopez]

Oops! I completely missed those test failures because I thought they were part of the known package test failures and didn't even check them 😅

Thanks for noticing! I will take a look 👍

[davelopez]

Looks like @nsoranzo suggestion worked! Only unrelated test failures now :)