In widget.Form, Validateable items don't show their error text unless they are widget.Entry or have HintText set

[ncw]

Checklist

• I have searched the issue tracker for open issues that relate to the same problem, before opening a new one.
• This issue only relates to a single bug. I will open new issues for any other problems.

Describe the bug

When creating a widget.Form if the widget satisfies the widget the fyne.Validatable then it should show red error text if the validation fails.

However this only happens for widget.Entry or with form items with HintText set.

How to reproduce

First run the program below. You will see that it creates a form with two validated items. The plain one works fine, but the wrapped one does not - the error text does not appear.

If you then uncomment the line //formItem.HintText = "Hint" // Hint needs to be not "" to make validation appear then the error text will appear.

PS Note you need to type something in the box and delete it to get the error message to appear - not sure if this is working as intended or not!

Screenshots

Form without HintText set - notice the validation line is not appearing for the "with help" widget

Now with HintText set

And showing the error

Example code

package main

import (
	"errors"
	"fmt"

	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/theme"
	"fyne.io/fyne/v2/widget"
)

// Wrap any widget with a help button next to it
type WithHelp struct {
	widget.BaseWidget
	originalWidget fyne.CanvasObject
	helpButton     *widget.Button
	content        *fyne.Container
}

// check interfaces
var _ fyne.Validatable = &WithHelp{}

// Create a new widget with a help button next to it
//
// Aims to preserve the Validateable status of the wrapped widget
func NewWithHelp(originalWidget fyne.CanvasObject, helpText string) *WithHelp {
	h := &WithHelp{
		originalWidget: originalWidget,
		helpButton: widget.NewButtonWithIcon("", theme.HelpIcon(), func() {
			fyne.CurrentApp().SendNotification(&fyne.Notification{
				Title:   "Help",
				Content: helpText,
			})
		}),
	}
	h.content = container.NewBorder(nil, nil, nil, h.helpButton, h.originalWidget, h.helpButton)
	h.ExtendBaseWidget(h)
	return h
}

// Render the combined originalWidget and helpButton
func (h *WithHelp) CreateRenderer() fyne.WidgetRenderer {
	return widget.NewSimpleRenderer(h.content)
}

// Forward Validate if possible to originalWidget
func (h *WithHelp) Validate() error {
	if do, ok := h.originalWidget.(fyne.Validatable); ok {
		err := do.Validate()
		h.Refresh() // Update the widget's appearance based on validation state
		return err
	}
	return nil
}

// Forward SetOnValidationChanged if possible to originalWidget
func (h *WithHelp) SetOnValidationChanged(callback func(error)) {
	if do, ok := h.originalWidget.(fyne.Validatable); ok {
		do.SetOnValidationChanged(func(err error) {
			callback(err)
			h.Refresh() // Update the widget's appearance when validation changes
		})
	}
}

func main() {
	myApp := app.New()
	myWindow := myApp.NewWindow("Form test with Validateable widget")

	// Create an entry widget with validation then wrap it in a WithHelp
	entry := widget.NewEntry()
	entry.Validator = func(val string) error {
		if val == "" {
			return errors.New("Can't be empty")
		}
		return nil
	}
	withHelp := NewWithHelp(entry, "This is help text for item1")

	// Create an plain entry widget with validation
	entryPlain := widget.NewEntry()
	entryPlain.Validator = func(val string) error {
		if val == "" {
			return errors.New("Can't be empty")
		}
		return nil
	}

	formItem := widget.NewFormItem("with help", withHelp)
	//formItem.HintText = "Hint" // Hint needs to be not "" to make validation appear

	plainFormItem := widget.NewFormItem("plain", entryPlain)

	form := widget.NewForm(
		formItem,
		plainFormItem,
	)
	form.OnSubmit = func() {
		fmt.Println("Submit")
	}
	form.OnCancel = func() {
		myWindow.Close()
		fmt.Println("Cancel")
	}

	myWindow.SetContent(container.NewVBox(form))
	myWindow.Resize(fyne.NewSize(400, 10))
	myWindow.ShowAndRun()
}

Fyne version

7d81356 (master)

Also replicates on

1325f0d (develop)

Go compiler version

go1.23.2

Operating system and version

Ubuntu 22.04.5 LTS

Additional Information

I looked at trying to fix this. I think this is caused by the specific casts to *Entry here

fyne/widget/form.go

Lines 353 to 356 in 7d81356

	showHintIfError := false
	if e, ok := item.Widget.(*Entry); ok && (!e.dirty || e.focused) {
	showHintIfError = true
	}

But I'm not confident enough I understand the problem to fix it, but willing to have a go given a hint!

[andydotxyz]

I looked at trying to fix this. I think this is caused by the specific casts to *Entry here

You're probably right - there are other tickets open about how Validation has some Entry special code.
I think there was a prior PR for a related fix that someone opened but did not complete. Could be good to resolve this as suggested above before the larger validation fixes get revisited