env._.source scripts should be able to modify the PATH

[Mossop]

Describe the bug
A shell script sources by env._.source cannot modify the PATH environment variable.

To Reproduce

In a new directory:
Create a test.sh file:

export PATH="/Users/dave/test:$PATH"
export FOO_TEST="bar"

and a .mise.toml:

[env]
_.source = "test.sh"

Expected behavior
The FOO_TEST environment variable should be set and the change should be made to the PATH environment variable but only the first happens.

mise doctor output

version: 2024.12.12 macos-arm64 (2d9d289 2024-12-16)
activated: yes
shims_on_path: no

build_info:
  Target: aarch64-apple-darwin
  Features: DEFAULT, NATIVE_TLS, OPENSSL
  Built: Mon, 16 Dec 2024 18:21:21 +0000
  Rust Version: rustc 1.83.0 (90b35a623 2024-11-26)
  Profile: release

shell:
  /opt/homebrew/bin/bash
  GNU bash, version 5.2.37(1)-release (aarch64-apple-darwin24.0.0)
  Copyright (C) 2022 Free Software Foundation, Inc.
  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

  This is free software; you are free to change and redistribute it.
  There is NO WARRANTY, to the extent permitted by law.

dirs:
  cache: ~/Library/Caches/mise
  config: ~/.config/mise
  data: ~/.local/share/mise
  shims: ~/.local/share/mise/shims
  state: ~/.local/state/mise

config_files:
  ~/.mise.toml
  ~/test/.mise.toml

backends:
  aqua
  asdf
  cargo
  core
  gem
  go
  npm
  pipx
  spm
  ubi
  vfox

plugins:

toolset:

path:
  ~/bin
  ~/.local/bin
  ~/dotfiles/platforms/macos/bin
  ~/dotfiles/bin
  /Applications/Visual Studio Code.app/Contents/Resources/app/bin
  /opt/homebrew/opt/curl/bin
  /opt/homebrew/opt/coreutils/libexec/gnubin
  /opt/homebrew/opt/grep/libexec/gnubin
  /opt/homebrew/opt/gnu-tar/libexec/gnubin
  /opt/homebrew/opt/gnu-sed/libexec/gnubin
  /opt/homebrew/opt/findutils/libexec/gnubin
  /opt/homebrew/opt/gnu-which/libexec/gnubin
  /opt/homebrew/bin
  /opt/homebrew/sbin
  /usr/local/bin
  /System/Cryptexes/App/usr/bin
  /usr/bin
  /bin
  /usr/sbin
  /sbin
  /var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin
  /var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin
  /var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin
  ~/.atuin/bin
  ~/.cargo/bin

env_vars:
  MISE_SHELL=bash

settings:
  experimental       true ~/.mise.toml
  status.show_tools  true ~/.mise.toml

No problems found```

**Additional context**

[jdx]

I believe you can but it may not be documented since this was something I needed for unrelated things in mise's internals I never intended to expose—except to possibly plugin devs.

You can set MISE_ADD_PATH which will be inserted at the beginning. There is also MISE_RM_PATH. Removals are something idk if I ever actually do in mise so removing may not work at all.

There is logic in mise to diff 2 PATH variables so this could also work in the way you're expecting, but since I only needed this for internal logic it wasn't necessary at the time to put the diffing into _.source.

I also kind of prefer _.source since if you do something crazy with PATH the diffing logic could fail or maybe even do something you definitely didn't want. 9/10 times though people just insert at the front though. Maybe more like 99/100.

[Mossop]

I just tried with export MISE_ADD_PATH="..." and all it did was add that as an environment variable.

[jdx]

alright thanks for checking, I think this should work the way you originally expected by modifying PATH directly