User fish functions named like built-ins break the vp wrapper and vpr completion in env.fish #3128

Describe the bug

The generated env.fish calls some fish built-in commands by their bare names. These commands are count, math, contains, complete, and commandline. fish looks for a function before a built-in. fish also autoloads a function from ~/.config/fish/functions/<name>.fish when a script first calls the name. Thus, if a user has a function with one of these names, env.fish calls the user's function and not the built-in.

fish still starts and shows no error. But the vp wrapper and the vpr completion work incorrectly.

The count case causes the most harm. vp env use shows a success message, and the user thinks that the Node.js version changed. But the shell still uses the previous version.

env.fish can call these commands with the builtin keyword, for example builtin count. fish does not let a user define a function named builtin, and all supported fish versions have this keyword. With builtin, the count, math, and complete cases work correctly. I did not check the commandline case with builtin.

A user function named contains or source breaks the startup of fish itself. fish then does not read conf.d at all. env.fish cannot prevent this case.

#3092 reports the same class of problem for Nushell. In Nushell, the result is a parse error at startup. In fish, the result is incorrect behavior without an error.

Reproduction

No repository is necessary. The steps use only vp and fish, and they write only to a temporary directory.

Steps to reproduce

1. Generate env.fish in a temporary directory, so that no real shell profile changes.

    R=$(mktemp -d)
    HOME=$R/home ZDOTDIR=$R/home XDG_CONFIG_HOME=$R/setup-config VP_HOME=$R/vp vp env setup --env-only
   

2. Make a fish configuration directory. conf.d/vite-plus.fish sources env.fish, as vp env setup does. functions/count.fish is the user's function.

    mkdir -p "$R/case-count/fish/conf.d" "$R/case-count/fish/functions"
    printf 'source "%s"\n' "$R/vp/env.fish" > "$R/case-count/fish/conf.d/vite-plus.fish"
    printf 'function count\n    echo 0\nend\n' > "$R/case-count/fish/functions/count.fish"
   

3. Start fish with this configuration.

    cd "$R"
    env -u VP_NODE_VERSION XDG_CONFIG_HOME="$R/case-count" HOME="$R/case-count" VP_HOME="$R/vp" fish
   

4. In fish, run these commands.

    vp env use 20.18.0 --no-install
    echo $VP_NODE_VERSION
   

Expected result: echo $VP_NODE_VERSION prints 20.18.0.

Actual result: vp env use prints Using Node.js v20.18.0 (resolved from 20.18.0), but echo $VP_NODE_VERSION prints an empty line.

Without functions/count.fish, the same steps print 20.18.0.

#!/bin/sh
set -eu
VP=${VP:-vp}
FISH=${FISH:-fish}
R=$(mktemp -d)
HOME=$R/home ZDOTDIR=$R/home XDG_CONFIG_HOME=$R/setup-config VP_HOME=$R/vp \
  "$VP" env setup --env-only </dev/null >/dev/null
mkdir -p "$R/project"
printf '{ "name": "demo", "scripts": { "build": "echo build" } }\n' > "$R/project/package.json"

run() {
  dir=$R/case-$1
  mkdir -p "$dir/fish/conf.d" "$dir/fish/functions"
  printf 'source "%s"\n' "$R/vp/env.fish" > "$dir/fish/conf.d/vite-plus.fish"
  [ "$1" = none ] || printf 'function %s\n    %s\nend\n' "$1" "$2" > "$dir/fish/functions/$1.fish"
  (cd "$R" && env -u VP_NODE_VERSION XDG_CONFIG_HOME="$dir" HOME="$dir" VP_HOME="$R/vp" \
    "$FISH" -i -c "$3" </dev/null 2>&1) || true
}

USE='vp env use 20.18.0 --no-install >/dev/null 2>&1; echo "VP_NODE_VERSION=[$VP_NODE_VERSION]"'
USE_C='vp -C project env use 20.18.0 --no-install >/dev/null 2>&1; echo "VP_NODE_VERSION=[$VP_NODE_VERSION]"'
COMPLETE='echo "vpr completion rules: $(builtin complete -c vpr | builtin count)"'
CANDIDATES='echo "candidates for \"vpr -C project \": [$(builtin complete -C "vpr -C project ")]"'

echo "== count";       run none '' "$USE";        run count 'echo 0' "$USE"
echo "== math";        run none '' "$USE_C";      run math 'echo 99' "$USE_C"
echo "== complete";    run none '' "$COMPLETE";   run complete 'true' "$COMPLETE"
echo "== commandline"; run none '' "$CANDIDATES"; run commandline 'true' "$CANDIDATES"

== count
VP_NODE_VERSION=[20.18.0]
VP_NODE_VERSION=[]
== math
VP_NODE_VERSION=[20.18.0]
VP_NODE_VERSION=[]
== complete
vpr completion rules: 1
vpr completion rules: 0
== commandline
candidates for "vpr -C project ": []
candidates for "vpr -C project ": [run	Run tasks]

System Info

vp v1.3.0
fish 4.9.3
macOS

Used Package Manager

npm

Logs

No error appears. The "Steps to reproduce" section shows the output.

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.