Transient prompt (#10391)

## Description

This PR uses environment variables to enable and set a transient prompt,
which lets you draw a different prompt once you've entered a command and
you've moved on to the next line. This is useful if you have a fancy
two-line prompt with a bunch of info about time and git status that you
don't really need in your scrollback buffer.

Here's a screenshot. You can see how my usual prompt has two lines and
would take up a lot more space if every past command also used the full
prompt, but reducing past prompts to `🚀` or `>` makes it take up less
space.

![image](https://github.com/nushell/nushell/assets/45539777/dde8d0f5-f95f-4529-9a14-b7919bd51126)

I added the following lines to my `env.nu` to get that rocket as the
prompt initially:
```nu
$env.TRANSIENT_PROMPT_COMMAND = {|| "" }
$env.TRANSIENT_PROMPT_INDICATOR = {|| open --raw "~/.prompt-indicator" }
$env.TRANSIENT_PROMPT_INDICATOR_VI_INSERT = $env.TRANSIENT_PROMPT_INDICATOR
```

## User-Facing Changes

If you want to change a segment of the prompt, set the corresponding
`TRANSIENT_PROMPT_*` variable.

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## Problems/Things to Consider:
- The transient prompt clones the `Stack` at the very beginning of the
session and keeps that around. I'm not sure if that could cause
problems, but if so, it could probably take an `Arc<State>` instead.
- This isn't truly a problem, but now there's even more environment
variables, which is kinda annoying.
- There might be some performance issues with creating a new
`NushellPrompt` object and cloning the `Stack` for every segment of the
transient prompt. What's more, the transient prompt is added to the
`Reedline` object whether or not the user has enabled transient prompt,
so if there are indeed performance issues, simply disabling the
transient prompt won't help.
- Perhaps instead of a separate `TRANSIENT_PROMPT_INDICATOR_VI_INSERT`
and `TRANSIENT_PROMPT_INDICATOR_VI_NORMAL`, `TRANSIENT_PROMPT_INDICATOR`
could be used for both (if it exists). Insert and normal mode don't
really matter for previously entered commands.
This commit is contained in:
Yash Thakur
2023-09-22 15:35:09 -04:00
committed by GitHub
parent 6df001f72d
commit 414216edfa
3 changed files with 144 additions and 1 deletions

View File

@ -47,6 +47,18 @@ $env.PROMPT_INDICATOR_VI_INSERT = {|| ": " }
$env.PROMPT_INDICATOR_VI_NORMAL = {|| "> " }
$env.PROMPT_MULTILINE_INDICATOR = {|| "::: " }
# If you want previously entered commands to have a different prompt from the usual one,
# you can uncomment one or more of the following lines.
# This can be useful if you have a 2-line prompt and it's taking up a lot of space
# because every command entered takes up 2 lines instead of 1. You can then uncomment
# the line below so that previously entered commands show with a single `🚀`.
# $env.TRANSIENT_PROMPT_COMMAND = {|| "🚀 " }
# $env.TRANSIENT_PROMPT_INDICATOR = {|| "" }
# $env.TRANSIENT_PROMPT_INDICATOR_VI_INSERT = {|| "" }
# $env.TRANSIENT_PROMPT_INDICATOR_VI_NORMAL = {|| "" }
# $env.TRANSIENT_PROMPT_MULTILINE_INDICATOR = {|| "" }
# $env.TRANSIENT_PROMPT_COMMAND_RIGHT = {|| "" }
# Specifies how environment variables are:
# - converted from a string to a value on Nushell startup (from_string)
# - converted from a value back to a string when running external commands (to_string)