Nushell env bug: Positional completer input deprecated #3092

Describe the bug

Report

Nushell will not start on a machine where the user has defined a custom command
whose name collides with a builtin used by the generated completion file. The error
points at a file the user never wrote, so it reads as a vite-plus or Nushell bug
rather than a name collision in the user's own config.

Environment: vite-plus v1.3.0, Nushell 0.116.1, Arch Linux.

The trigger on my machine was an ordinary helper:

# ~/.config/nushell/aliases.nu
def update [] {          # <-- Update system and Flatpaks
  yay; flatpak update
}

Nothing in my dotfiles references vite-plus. Opening Nushell fails with:

Error: nu::parser::extra_positional_argument

  x Extra positional argument.
    ,-[/home/USER/.config/vite-plus/env.nu:43:111]
 42 |     let fish_cmd = $"VP_COMPLETE=fish command vp | source; complete '--do-complete=($context)'"
 43 |     fish --command $fish_cmd | from tsv --flexible --noheaders --no-infer | rename value description | update value {|row|
    :                                                                                                               ^^|^^
    :                                                                                                                 `-- extra positional argument
 44 |         let value = $row.value
    `----
  help: Usage: update

There is no prompt, no REPL, no way to fix it from inside the shell. The file has to
be edited by hand.

Mechanism

This is what makes it hard to report. vite-plus registers itself with Nushell by
writing a file into the auto-load directory; Nushell sources every .nu file there at
startup:

$ ls -la "$(nu -c '$nu.data-dir')/vendor/autoload/"
-rw-r--r-- 1 user user 81 ... vite-plus.nu

$ cat "$(nu -c '$nu.data-dir')/vendor/autoload/vite-plus.nu"
# Vite+ bin (https://viteplus.dev)
source "/home/josel/.config/vite-plus/env.nu"

So the load chain is:

~/.config/nushell/config.nu            -> source ~/.config/nushell/aliases.nu   (defines `update`)
$nu.data-dir/vendor/autoload/vite-plus.nu -> source ~/.config/vite-plus/env.nu   (calls builtin `update`)

In Nushell, def creates a global custom command, so def update [] shadows the
built-in update <field> <replacement> for the entire session. The generated
env.nu calls the built-in at line 43, and Nushell fails at parse time, before
executing anything.

Two details worth calling out:

• alias update = sysupdate does not work as a workaround. Aliases shadow too.
• Any built-in can be shadowed this way, so this is not specific to update. A user
  command named select, where, rename, str, path, etc. would collide the
  same way.

Evidence

Reproduction

https://gist.github.com/Kat404/4e275bbbcfa79f69182fd1a75dda1565

Steps to reproduce

Steps to reproduce

Requires Nushell only. Steps 1 and 2 do not need vite-plus installed and do not
break your own shell.

1. Minimal repro, no vite-plus, ~5 seconds

R=$(mktemp -d); mkdir -p "$R/cfg/nushell" "$R/data/nushell/vendor/autoload"
printf 'def update [] { echo shadowed }\n' > "$R/cfg/nushell/aliases.nu"
printf 'source %s/cfg/nushell/aliases.nu\n' "$R" > "$R/cfg/nushell/config.nu"
printf 'source "%s/env.nu"\n' "$R" > "$R/data/nushell/vendor/autoload/vite-plus.nu"
printf '[[a b]; [1 2]] | update a {|row| $row.a }\n' > "$R/env.nu"
printf 'exit\n' | XDG_CONFIG_HOME="$R/cfg" XDG_DATA_HOME="$R/data" nu

Expected:

Error: nu::parser::extra_positional
  x Extra positional argument.
   ,-[.../env.nu:1:25]
 1 | [[a b]; [1 2]] | update a {|row| $row.a }
   :                         |
   :                         `-- extra positional argument

2. Same failure against the real generated file (safe, does not touch your config)

printf 'def update [] { }\n' > /tmp/shadow.nu
nu -c 'source /tmp/shadow.nu; source ~/.config/vite-plus/env.nu'

Expected: extra positional argument at env.nu:43:111 with help: Usage: update,
matching the report above exactly.

3. Control

nu -c 'def sysupdate [] { }; source ~/.config/vite-plus/env.nu; print "loads clean"'

Expected: loads clean. The only difference is the command name.

4. Deterministic container, Docker or Podman

https://gist.github.com/Kat404/4e275bbbcfa79f69182fd1a75dda1565

curl -O https://gist.githubusercontent.com/Kat404/4e275bbbcfa79f69182fd1a75dda1565/raw/2a4623056500cc2a1fa202cd9af5643606192521/Containerfile
podman build -t nu-shadow-repro ./Containerfile
podman run --rm nu-shadow-repro

The Containerfile is self-contained and asserts both directions: the build fails if
the bug does not reproduce, and fails again if the renamed control case still breaks.

CASE A (def update []): BUG REPRODUCED
CASE B (def sysupdate []): config loads clean

Workaround

Rename the user command so it no longer shadows a built-in:

def sysupdate [] { yay; flatpak update }

Environment

• vite-plus v1.3.0
• Nushell 0.116.1 (/usr/bin/nu, official musl static release)
• Arch Linux, kernel 6.x, GNOME
• Generated file at fault: ~/.config/vite-plus/env.nu, line 43
• Auto-load shim: $nu.data-dir/vendor/autoload/vite-plus.nu
• Podman 6.1.4 for the container repro
• Note: Nushell 0.116.1 prints the error code as nu::parser::extra_positional;
  older/other builds print nu::parser::extra_positional_argument. Same defect.

System Info

$ vp env current
VITE+ - The Unified Toolchain for the Web

Node.js:
  Version    26.11.1
  Source     system PATH
  Bin Path   /usr/bin/node
  Installed  true
  Mode       system_first

$ vp --version
VITE+ - The Unified Toolchain for the Web

vp v1.3.0

Local vite-plus:
  vite-plus  Not found

Tools:
  vite             Not found
  rolldown         Not found
  vitest           Not found
  oxfmt            Not found
  oxlint           Not found
  oxlint-tsgolint  Not found
  tsdown           Not found

Environment:
  Package manager  Not found
  Node.js          v24.22.0

Used Package Manager

pnpm

Logs

Validations

• Read the Contributing Guidelines.
• Check that there isn't already an issue for the same bug.
• Confirm this is a Vite+ issue and not an upstream issue (Vite, Vitest, tsdown, Rolldown, or Oxc).
• The provided reproduction is a minimal reproducible example.