Proposal: Data integrity

in old ATK we had a 'mandatory' flag that would require UI element to fail if user would leave entry empty. It has been a place of confusion, so this article is a proposal how to implement this in Agile Data:

Cases to consider:

UI framework presents a form with "name" field. User leaves field empty and hits save. Should operation be successful if "name" field is marked as mandatory?

• AD: Well, the field was presented but was empty string, so it's OK
• AD: If numeric value is mandatory and presented with value 0, it should be fine, right?
• AD: Would false value of a boolean field be mandatory?
• What if form has a mandatory checkbox and user does not click it. Is that an error?

Next set of questions says, who should do the validation:

• AD: Loaded record from DB where mandatory field is null. Error?
• AD: User manually created record ommitting mandatory field. Error?
• AD: User did set the field value to "NULL" explicitly. Error?

AD vs UI vs Validator:

• Should UI signal user about missing value?
• Mandatory fields may contain asterisk next to label. Where UI gets information about that?

Trickier cases:

• would empty array [] be permitted in mandatory field? (non-sql)
• what if date is mandatory. Would 0000-00-00 be an OK value?

Proposed Implementation:

• AD to only reject NULL for mandatory fields.
• UI form reads $field->mandatory flag and invokes necessary validation
• Validation framework can perform further validation (e.g. non-empty string, or non-zero)

Disagree? Willing to discuss?

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