**Background:**
Adding "soft" validation to the following fields should help users filling in templates to catch errors earlier on.
Parameter warnings by type of parameter:
| |** Param type** | **Expected value** | **Text** | **Type of message** |
| [x] | Number | any combination of 0-9 |This parameter expects only numerical values, 0-9. | Warning |
| [x] | Date | ISO 8601 (YYYY-MM-DD, YYYY, YYYY-MM, --MM-DD) | This parameter expects dates formatted in [[ https://en.wikipedia.org/wiki/ISO_8601#Dates | ISO 8601 ]].| Warning |
| [x] | Combobox | Suggested values as defined in TemplateData | [already implemented] This is not one of the suggested values and may not work with the template. | Notice |
| | File | Filename without file: prefix | This template likely expects a filename without prefix. If you experience issues, try removing it.| Notice |
Situation based warnings:
| |**Situation** | **Text** | **Type of Message** |
| | ~~Nested templates: When {{ }} is detected~~ | ~~Nested templates are not supported in the VisualEditor and must be edited in wikitext.~~ | ~~Notice~~ |
| [x] | Adding undefined parameters {T117890} | This user-added parameter may not be supported by the template. | Notice |
| [x] | Required parameters | [Switch current pop-up warning to inline warning] | Warning |
**Requirements:**
[x] Validation should appear in real time, but not before the user has stopped typing and clicked out of the field.
[x] Validation should provide enough flexibility to the user to continue with the value filled in if desired (i.e. validation should not block the user from saving).
[] Investigate: if there are any other "pop-up" warnings currently in place that should be changed to inline warnings.
**Mocks:**
Use OOUI FieldLayout with notice and FieldLayout with warning
{F32357727}