Preferences RemoveValue does not save

[chriselkins]

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

I have tested setting and removing values on Windows and Linux. I am able to set and write values to the preferences file but RemoveValue does not work. I'm using Fyne v2.2.3.

I can confirm on Linux that the code below creates a preferences file (~/.config/fyne/com.vitalitysouth.test/preferences.json) and that file contains the contents: {"num":42}

Even if I comment out or remove the Set() line, RemoveValue still will not remove the value from the preferences.json file.

package main

import (
	"fyne.io/fyne/v2/app"
)

func main() {
	a := app.NewWithID("com.vitalitysouth.test")
	w := a.NewWindow("Test")

	a.Preferences().SetInt("num", 42)

	a.Preferences().RemoveValue("num")

	w.ShowAndRun()
}

Relevant go.mod:

        fyne.io/fyne/v2 v2.2.3
        fyne.io/systray v1.10.1-0.20220621085403-9a2652634e93 // indirect
        github.com/fyne-io/gl-js v0.0.0-20220802150000-8e339395f381 // indirect
        github.com/fyne-io/glfw-js v0.0.0-20220517201726-bebc2019cd33 // indirect
        github.com/fyne-io/image v0.0.0-20220602074514-4956b0afb3d2 // indirect

How to reproduce

1. Create a bare bones fyne app.
2. Set a preference.
3. Try to use RemoveValue to remove the preference.

Screenshots

No response

Example code

package main

import (
	"fyne.io/fyne/v2/app"
)

func main() {
	a := app.NewWithID("com.vitalitysouth.test")
	w := a.NewWindow("Test")

	a.Preferences().SetInt("num", 42)

	a.Preferences().RemoveValue("num")

	w.ShowAndRun()
}

Fyne version

2.2.3

Go compiler version

1.19

Operating system

Linux

Operating system version

WSL Ubuntu 20.04

Additional Information

No response

[chriselkins]

I noticed that if I make a Set() call after the RemoveValue() call, then the RemoveValue() call will take effect. So, as a workaround, the following code allows RemoveValue() to work.

package main

import (
	"fyne.io/fyne/v2/app"
)

func main() {
	a := app.NewWithID("com.vitalitysouth.test")
	w := a.NewWindow("Test")

	a.Preferences().SetInt("num", 42)

	a.Preferences().RemoveValue("num")

	a.Preferences().SetInt("tmp", 43)

	w.ShowAndRun()
}

[andydotxyz]

On develop branch for next release