Usage of default prompt but with custom side effects in prompt function

[felixfbecker]

System Details

• posh-git version/path: 1.0.0.0 pre00 ~/git/posh-git/src
• PowerShell version: 6.0.0-beta
• git version 2.13.6 (Apple Git-96)
• OS: Unix 16.7.0.0 (macOS Sierra)

Issue Description

I want to customize my prompt function so that it checks whether the current directory has an .nvmrc file and switches Node versions depending on that. But I also want to keep the default git prompt. Is that possible?

[rkeithhill]

In theory you could do something like:

$GitPromptSettings.DefaultPromptPrefix = '$(if (Test-Path -LiteralPath $pwd/.nvmrc -EA 0) { <exec command> *> $null })'

Just keep in mind if any "output" returned by this would get displayed before the default posh-git prompt, hence the redirect to $null. You might notice a bit of slow down in your prompt display in directories containing a .nvmrc file.

[vegar]

will this be executed more then once though?
I've tried adding a timestamp to the prompt, but the timestamp is evaluated once and then remain the same for the lifetime of the shell...

[rkeithhill]

Be careful to use single quotes when supplying the string. If you use double quotes, any variables / subexpressions i.e. $() will only get eval'd once.

[rkeithhill]

@felixfbecker What if we created another global variable (like $GitPromptSettings) called $GitPromptScriptBlock that you could invoke from your own prompt function e.g.:

function prompt {
    # ... script to do stuff like switch node versions
    &$GitPromptScriptBlock
}

I've prototyped this and it works fine in my testing. I might include this in the upcoming 1.0.0 beta. Sure would love to have you test it on macOS.

BTW I wonder if we should call this variable $PoshGitPromptScriptBlock to lessen chances of collision? But if we do that, it kind of implies we should change $GitPromptSettings to $PoshGitPromptSettings. I guess it is unlikely that a user would have two different modules trying to provide Git prompt functionality as that just isn't going to work well.

[dahlbyk]

Or, going the other direction, we could add $GitPromptSettings.OnPrompt (better name?) that we'll execute if set. Seems preferable to avoid folks needing to write their own prompt.

[rkeithhill]

We could actually do both. Allowing users to inject custom script via a ScriptBlock would be handy. But exposing $GitPromptScriptBlock is just a minor tweak i.e. change the variable name slightly and export it. We're already creating the scriptblock. I could see this being handy for more advanced users that want to write their own prompt function but want to invoke posh-git one as well.

[dahlbyk]

We're already creating the scriptblock. I could see this being handy for more advanced users that want to write their own prompt function but want to invoke posh-git one as well.

👍

[rkeithhill]

What if we made this change just for 1.0.0? @felixfbecker is on PS Core, so he'd be covered.

[rkeithhill]

@felixfbecker Would you be willing to try out the rkeithhill/refactor-write-prompt branch in this repo? Basically git clone the repo, checkout that branch and in your profile import posh-git using the path to where you cloned it e.g.:

function prompt {
    # ... script to do stuff like switch node versions
    if ($GitPromptScriptBlock) { &$GitPromptScriptBlock }
}
import-module ~/github/posh-git/src/posh-git.psd1

I added in the guard just in case you remove the posh-git module.

[felixfbecker]

I'm curious why it is a dynamic script block and not just a function like Write-GitPrompt?

Checked out the branch to test but struggling with #486

[rkeithhill]

Because we assign that scriptblock to the prompt function i.e. that's how we "set" the prompt function.

Set-Item Function:\prompt -Value $GitPromptScriptBlock

[rkeithhill]

RE #486 - try setting:

$global:GitPromptSettings.DefaultPromptSuffix = '`n$(''>'' * ($nestedPromptLevel + 1)) '

That is supposed to get rid of the double prompt. Of course, PSReadline 2.0.0-beta1 is supposed to fix these issues. BTW I had a bear of a time to get my PS Core in WSL/Ubuntu to use the new version of PSReadline. I had to resort to importing it by path.

[felixfbecker]

So PS Core 6.0.0-rc2 solved the readline issue.
With just this profile:

function prompt {
    &$GitPromptScriptBlock
}
Import-Module ~/git/posh-git/src/posh-git.psd1

I get this prompt:

PowerShell v6.0.0-rc.2
Copyright (c) Microsoft Corporation. All rights reserved.

https://aka.ms/pscore6-docs
Type 'help' to get help.

Loading personal and system profiles took 655ms.
/Users/felix> cd ./git/posh-git/
/Users/felix/git/posh-git [rkeithhill/refactor-write-prompt ≡]> 

But if I add:

function prompt {
    Set-NodeVersion
    &$GitPromptScriptBlock
}
Import-Module ~/git/posh-git/src/posh-git.psd1
Import-Module nvm

I get nothing:

PowerShell v6.0.0-rc.2
Copyright (c) Microsoft Corporation. All rights reserved.

https://aka.ms/pscore6-docs
Type 'help' to get help.

Loading personal and system profiles took 658ms.
PS>cd ./git/posh-git/
PS>

[rkeithhill]

Does Set-NodeVersion output anything? You might try Set-NodeVersion *> $null.

[felixfbecker]

Ah, Set-NodeVersion throws an exception if there is no version given and no .nvmrc found. Weird that the exception is not printed. A try/catch works.

[felixfbecker]

I think this is therefor solved :)