Reordered prompt done callback to avoid accessing out of bound history

[Neko-Box-Coder]

According to https://pkg.go.dev/github.com/zyedidia/micro/v2@v2.0.13/internal/info#InfoBuf.Prompt
A lua script can provide a done callback when the prompt has finished (enter is pressed).

This works fine until the done callback itself wants to have another prompt, for example multiple questions to configure an action.

The behavior in main right now will crash with

Micro encountered an error: runtime.boundsError runtime error: index out of range [22] with length 22
runtime/panic.go:114 (0x43c59c)
github.com/zyedidia/micro/v2/internal/action/infopane.go:115 (0x8d658f)
github.com/zyedidia/micro/v2/cmd/micro/micro.go:478 (0x90e0a6)
github.com/zyedidia/micro/v2/cmd/micro/micro.go:397 (0x90d9af)
runtime/internal/atomic/types.go:194 (0x44111d)
runtime/asm_amd64.s:1695 (0x4754e1)

If you can reproduce this error, please report it at https://github.com/zyedidia/micro/issues

So if I have something like this

micro.InfoBar():Prompt("Question 1 > ", "", "", nil, OnQuestion1Done)

local Answer1 = ""

function OnQuestion1Done(resp, cancelled)
    if cancelled then return end
    Answer1 = resp
    micro.InfoBar():Prompt("Question 2 > ", "", "", nil, OnQuestion2Done)
end


function OnQuestion2Done(resp, cancelled)
    if cancelled then return end
    -- Do something with Answer1 and resp...
end

It won't work and crash inside the 2nd prompt.

This is due to the 2nd call in the prompt trying to access history while the first prompt has not finished modifying the history.
See

micro/internal/info/infobuffer.go

Lines 97 to 109 in e9bd1b3

	func (i *InfoBuf) Prompt(prompt string, msg string, ptype string, eventcb func(string), donecb func(string, bool)) {
	// If we get another prompt mid-prompt we cancel the one getting overwritten
	if i.HasPrompt {
	i.DonePrompt(true)
	}
	if _, ok := i.History[ptype]; !ok {
	i.History[ptype] = []string{""}
	} else {
	i.History[ptype] = append(i.History[ptype], "")
	}
	i.HistoryNum = len(i.History[ptype]) - 1
	i.HistorySearch = false

and

micro/internal/info/infobuffer.go

Lines 150 to 154 in e9bd1b3

	resp := string(i.LineBytes(0))
	i.Replace(i.Start(), i.End(), "")
	i.PromptCallback(resp, false)
	h := i.History[i.PromptType]
	h[len(h)-1] = resp

where line 152 is calling the done callback and we are still modifying the history for the current prompt on line 153+

The proposed solution just needs to reorder the done callback to the end of the block where we have finished modifying the history so that the next prompt call can safely modify it.

[dmaluka]

where line 152 is calling the done callback and we are still modifying the history for the current prompt on line 153+

More precisely, what happens is:

1. DonePrompt() calls your OnQuestion1Done callback, which calls Prompt() which adds a new (empty) item to the history:

i.History[ptype] = append(i.History[ptype], "")

2. After that, DonePrompt() incorrectly writes the last entered text from the 1st prompt to this newly created history item for the 2nd prompt:

h := i.History[i.PromptType]
h[len(h)-1] = resp

since it doesn't realize that len(h) has changed and thus this is a wrong item, it should write to the last-but-one item instead.

3. After that, DonePrompt() itself immediately detects that this new history item is a duplicate (since DonePrompt() itself has just assigned it with the same text as the previous history item) and incorrectly removes it from the list.

4. So the history item for the 2nd prompt no longer exists. So when micro tries to access this history item when handling the 2nd prompt, it crashes.

Anyway, your fix looks correct.

[dmaluka]

nit: add empty line above this line?

[Neko-Box-Coder]

Done

[dmaluka]

Please remove spaces from this empty line.

[Neko-Box-Coder]

Done

[dmaluka]

Merged, thanks.