Value validator from array of items

[bjarnef]

Currently we have a validator here, which is used for an array of items (string array) like dropdown, radiobutton and checkbox lists:
https://github.com/umbraco/Umbraco-CMS/blob/fc60b5b5ffa1db5f9f1ee786f65ad33c9f44f4e3/src/Umbraco.Infrastructure/PropertyEditors/ValueListUniqueValueValidator.cs

A few issues:

• When validating it assumes property is named items although it probably works anyway as object value is passed in, but can it handle the name correct here?
  

  Umbraco-CMS/src/Umbraco.Infrastructure/PropertyEditors/ValueListUniqueValueValidator.cs

  Lines 41 to 58 in fc60b5b

  	if (items is null)
  	{
  	yield return new ValidationResult($"The configuration value {value} is not a valid value list configuration", ["items"]);
  	yield break;
  	}
  	var duplicateValues = items
  	.Select(item => item)
  	.GroupBy(v => v)
  	.Where(group => group.Count() > 1)
  	.Select(group => group.First())
  	.ToArray();
  	foreach (var duplicateValue in duplicateValues)
  	{
  	yield return new ValidationResult($"The value \"{duplicateValue}\" must be unique", new[] { "items" });
  	}
  	}

• Color Picker used a custom one, which is probably fine as it does some special regex for hex value, but it would be great it handle items as well if one re-use this in a configuration of a custom property editor:
  

  Umbraco-CMS/src/Umbraco.Infrastructure/PropertyEditors/ColorPickerConfigurationEditor.cs

  Lines 47 to 59 in fc60b5b

  	if (items is null)
  	{
  	yield return new ValidationResult($"The configuration value {stringValue} is not a valid color picker configuration", new[] { "items" });
  	yield break;
  	}
  	foreach (ColorPickerConfiguration.ColorPickerItem item in items)
  	{
  	if (Regex.IsMatch(item.Value, "^([0-9a-f]{3}|[0-9a-f]{6})$", RegexOptions.IgnoreCase) == false)
  	{
  	yield return new ValidationResult($"The value {item.Value} is not a valid hex color", new[] { "items" });
  	}
  	}

• Assuming we sometime later support value/label for dropdown etc. it will be useful if ValueListUniqueValueValidator can handle value in array of objects - or perhaps a different validator.
  Configurate text and value for prevalues in dropdown #11084

[bjarnef]

It doesn't seems we have much info about property except the value:

It seems it is called here:
https://github.com/umbraco/Umbraco-CMS/blob/main/src/Umbraco.Core/PropertyEditors/ConfigurationEditor.cs#L89

@AndyButland @Zeegaan it is possible we can pass in field here? So "items" isn't hardcoded?

Of course it can just be called "items" all the time, but what if one has two "items" (items 1 and 2) property in a more complex configuration or want to use same validator for two configuration properties in two different property editor (but we don't want to re-invent the wheel).

[kjac]

We had a chat about this internally, and we feel that validators should be self-contained.

That being said, it makes sense to build for reuse. Perhaps this could be solved by introducing an abstract base class for the ValueListUniqueValueValidator which lets the concrete implementation provide a field name for the validation?