Add storage API to open a file for appending, without truncating it's content first

[mbaklor]

Implemented in both memory and desktop, need to implement for mobile still, setting this as a draft for now, I don't know who can do mobile and how but for now this is what I could pull off.

Description:

Needed an option to add to a file in the storage without truncating it first, specifically to write long lasting log files.

Fixes #(issue)

Checklist:

• Tests included.
• Lint and formatter run with no errors.
• Tests all pass.

Where applicable:

• Public APIs match existing style and have Since: line.

[andydotxyz]

Clear and clean, thanks for looking at this - a good addition.

I think it will need the mobile code added to land though.
Would tips on how to progress be sufficient, or are you handing this on to someone else?

[mbaklor]

Thank you that was super encouraging and got me the drive to try the mobile code myself!

Let me know if this mobile code makes sense to you, and if someone with an android or ios setup - well - set up could check that this code works I'd super appreciate it as well!

[andydotxyz]

Looking great. The code compiles and runs on my iOS test devices.
But there is no test for the file repository on mobile.
Is there a snippet of code that could be run, or an example we could drop into fyne_demo that would verify?

Thanks!

[mbaklor]

I have discovered in writing this test snippet that I in fact forgot to implement the last part of the puzzle, the storage interface itself. Fixed and pushed, and here's the snippet I used to check it on my PC

func main() {
	app := app.NewWithID("io.fyne.appendtest")
	win := app.NewWindow("Append Test")
	win.Resize(fyne.NewSize(400, 300))

	app.Storage().Create("test.txt")

	btnAppend := widget.NewButton("append to file", func() {
		doc, err := app.Storage().Append("test.txt")
		if err != nil {
			dialog.ShowError(err, win)
			return
		}
		_, err = doc.Write([]byte("test line\n"))
		if err != nil {
			dialog.ShowError(err, win)
			return
		}
		err = doc.Close()
		if err != nil {
			dialog.ShowError(err, win)
			return
		}
		dialog.ShowInformation("Success", "Wrote to file", win)
	})
	btnRead := widget.NewButton("read file", func() {
		doc, err := app.Storage().Open("test.txt")
		if err != nil {
			dialog.ShowError(err, win)
			return
		}
		b := make([]byte, 64)
		_, err = doc.Read(b)
		if err != nil {
			dialog.ShowError(err, win)
			return
		}
		dialog.ShowInformation("Success", "Successfully read from file\n\ncontents:\n"+string(b), win)
		println(string(b))
	})

	content := container.NewGridWithRows(2, btnAppend, btnRead)
	win.SetContent(container.NewCenter(content))
	win.ShowAndRun()
}

[coveralls]

coverage: 59.969% (+0.008%) from 59.961%
when pulling 504b502 on mbaklor:storage-append
into de361f6 on fyne-io:develop.

[mbaklor]

the new "it works on my system" with the storage interface reverted to how it was is:

func main() {
	app := app.NewWithID("io.fyne.appendtest")
	win := app.NewWindow("Append Test")
	win.Resize(fyne.NewSize(400, 300))
	root := app.Storage().RootURI()
	uri, err := storage.Child(root, "test.txt")
	if err != nil {
		dialog.ShowError(err, win)
		return
	}

	btnAppend := widget.NewButton("append to file", func() {
		doc, err := storage.Appender(uri)
		defer doc.Close()
		if err != nil {
			dialog.ShowError(err, win)
			return
		}
		_, err = doc.Write([]byte("test line\n"))
		if err != nil {
			dialog.ShowError(err, win)
			return
		}
		dialog.ShowInformation("Success", "Wrote to file", win)
	})
	btnRead := widget.NewButton("read file", func() {
		doc, err := storage.Reader(uri)
		defer doc.Close()
		if err != nil {
			dialog.ShowError(err, win)
			return
		}
		b := make([]byte, 64)
		_, err = doc.Read(b)
		if err != nil {
			dialog.ShowError(err, win)
			return
		}
		dialog.ShowInformation("Success", "Successfully read from file\n\ncontents:\n"+string(b), win)
		println(string(b))
	})

	content := container.NewGridWithRows(2, btnAppend, btnRead)
	win.SetContent(container.NewCenter(content))
	win.ShowAndRun()
}

[andydotxyz]

Seems like this TODO could go?

[mbaklor]

OOPS! deleted

[andydotxyz]

Thanks for working on this. I think there is still a breaking change in the Repository interface API, but we have discussed how to resolve it. I left notes here as well which I hope help.

[andydotxyz]

This is the remaining breaking change where a new (optional) interface will be needed, perhaps AppendableRepository?

[andydotxyz]

Corresponding to the note above this should be a check for supporting the Appender