Field API: Validation

[oandregal]

Related: #72321

What

This is a tracking issue to break down the work on implementing validation in the Field API.

See related iteration issue and tracking issues for WordPress 6.9 and WordPress 7.0, as well as the comparison of validation in JSON Schema, Fields API, and HTML.

Goals

Support a number of general validation rules leveraging the HTML standard. If/when we introduce domain-specific types (e.g., slug), that would also support domain-specific validation. For the 1st iteration, we want to implement general validation, while supporting domain-specific validation via the isValid.custom.

Support both sync and async custom validation. In progress: controlled, uncontrolled.

Status

• not planned: -
• need to be implemented: empty cell
• shipped: ✅

	required	custom	pattern	min/max	elements[1]
array (field type & control)	✅	✅	-	-	✅
boolean (field type)	✅	✅	-	-	-
checkbox (control)	✅	✅	-	-	-
color (field type & control)	✅	✅	-	-	-
date (field type & control)	Use validated control	Use validated control	-	range of dates	-
datetime (field type & control)	Use validated control	Use validated control	-	range of dates	-
email (field type & control)	✅	✅	✅	max=maxlength, min unsupported	-
integer (field type & control)	✅	✅	-	controls the range of input	-
media (field type & control)	-	-	-	-	-
password (field type & control)	✅	✅	✅	controls the length of input (min=minlength, max=maxlength)	-
radio (control)	✅	✅	-	-	-
select (control)	✅	✅	-	-	-
telephone (field type & control)	✅	✅	✅	-	-
text (field type & control)	✅	✅	✅	controls the length of input (min=minlength, max=maxlength)	-
textarea	✅	✅	-	-	-
toggle (control)	✅	✅	-	-	-
toggleGroup (control)	✅	✅	-	-	-
url (field type & control)	✅	✅	✅	-	-

Notes:

• [1] The elements validation rule is something we have hardcoded in the custom function of some field types (example) and we aim to extract. In some contexts, the UI component would restrict already the inputs (e.g., via select component) but others would require to set elements: true to make it so (e.g., ValidatedFormTokenField for array).

Tasks

Any of these can be picked up by anyone. Refer to the status table above for details:

• Use ValidatedInputControl for date field type (support for required & custom validation)
• Use ValidatedInputControl for datetime field type (support for required & custom validation)
• Implement isValid.pattern validation #73156
• Implement isValid.min/isValid.max validation #73465

[oandregal]

@mirka @jameskoster I've taken stock of what we have and prepared a list of tasks. I think for WordPress 6.9 it'd be good to have all controls supporting required and custom validation.

I'd like to gather thoughts on what this means for date and datetime field types. I haven't found a validated calendar control, so I'm thinking that it'd be okay to just have the input with validation (using the ValidatedInputControl, that we'll also have in datetime as per #71509).

[mirka]

I'd like to gather thoughts on what this means for date and datetime field types. I haven't found a validated calendar control, so I'm thinking that it'd be okay to just have the input with validation (using the ValidatedInputControl, that we'll also have in datetime as per #71509).

Sounds fine to me 👍