feat: add --reinstall-packages-from flag to fnm install by amanthanvi · Pull Request #1505 · Schniz/fnm

amanthanvi · 2026-02-12T18:47:43Z

Summary

Adds --reinstall-packages-from=<version> flag to fnm install. When specified,
global npm packages from the source Node version are copied to the newly installed
version. This is the nvm-equivalent feature that has been the most requested
migration aid since 2022.

Motivation

Closes Support for reinstall packages from other versions #620
Refs Feature: Migrating Global Packages While Installing #703, Question: migrate global npm packages #481
Each Node version managed by fnm has isolated global packages. When users install
a new version, they lose all their CLI tools (eslint, prettier, typescript, etc.)
until manually reinstalled. This is the Unzip and untar #1 friction point for nvm-to-fnm migration.
nvm has supported --reinstall-packages-from for years; this brings parity.
Builds on the earlier attempt in feat: add --reinstall-packages-from= argument for fnm install #510, addressing all maintainer feedback:
cross-platform Windows support, comprehensive e2e tests, and proper error handling.

Implementation

Package listing (source version)

Runs npm ls --global --parseable --long --loglevel=error in the source version's
context using std::process::Command with PATH set to the source version's bin dir
Parses output to extract name@version pairs
Filters out npm and corepack (ship with Node, should not be reinstalled)

Package installation (target version)

Runs npm install --global <packages> via Exec::new_for_version() on the newly
installed target version
User sees real-time install progress (stdio inherited)

Error handling

Source version not installed → clear error message with suggestion
Source has no global packages → info message, not an error
npm command failures → wrapped in ReinstallPackagesError with context

Cross-platform

Unix: bin/npm paths
Windows: npm.cmd paths, ; PATH separator
Uses cfg!(windows) guards matching the existing enable_corepack() pattern

Usage

# Install v22 and copy all global packages from v24
fnm install 22 --reinstall-packages-from=24

# Works with aliases too
fnm install lts-jod --reinstall-packages-from=default

# If source has no packages, just prints info and continues
fnm install 18 --reinstall-packages-from=20
# "No global packages found in Node v20.x.x."

Testing

Unit tests for npm output parser (scoped packages, builtins filter, malformed lines)
E2E test: install package on version A, install version B with
--reinstall-packages-from=A, verify package present on B
E2E test: source not installed → error message
E2E test: source has no packages → graceful info message
Cross-platform: tested across Bash, Zsh, Fish, PowerShell, WinCmd

Checklist

cargo test passes
cargo clippy --all-targets clean
cargo fmt --check clean
E2E tests pass
Docs updated (commands.md)
Changeset added
Windows paths handled (npm.cmd, ; separator)
Addresses all feedback from feat: add --reinstall-packages-from= argument for fnm install #510 review

Copies global npm packages from a specified installed Node version to a newly installed version. Resolves the source version's global packages via `npm ls`, filters out builtins (npm, corepack), and installs them on the target version. Closes Schniz#620 Refs Schniz#703, Schniz#481

changeset-bot · 2026-02-12T18:47:48Z

🦋 Changeset detected

Latest commit: f3c174f

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
fnm	Minor

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vercel · 2026-02-12T18:47:49Z

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Pull request overview

This PR adds the highly requested --reinstall-packages-from flag to the fnm install command, bringing feature parity with nvm. This addresses a major pain point where users lose their global CLI tools (eslint, prettier, typescript, etc.) when installing new Node versions.

Changes:

Added --reinstall-packages-from flag to fnm install that copies global npm packages from a source Node version to the newly installed target version
Implemented package listing using npm ls --global --parseable --long with proper filtering of built-in packages (npm, corepack)
Added comprehensive e2e tests covering success, error, and edge cases
Updated documentation and added changeset

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/commands/install.rs	Core implementation including package listing, reinstallation logic, parser for npm output, cross-platform path handling, error types, and unit tests
e2e/reinstall-packages-from.test.ts	E2e tests for Bash and PowerShell covering package reinstallation, error handling when source not installed, and graceful handling of empty package lists
e2e/snapshots/reinstall-packages-from.test.ts.snap	Jest snapshots for the e2e tests
docs/commands.md	Documentation for the new --reinstall-packages-from flag
.changeset/shiny-ducks-reinstall.md	Changeset documenting this minor version feature addition

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amanthanvi · 2026-02-12T19:13:33Z

CI note (fork PR):\n- Rust workflow is currently "action_required" (needs maintainer approval to run).\n- Vercel status fails with "Authorization required to deploy" for forks.\n- Copilot code review run failed during artifact cleanup due to fork permissions.\nLocal checks passed: cargo build/test/clippy/fmt + pnpm test -- e2e/reinstall-packages-from.test.ts.

… the same Avoids a wasteful no-op reinstall cycle when a user passes the same version to --reinstall-packages-from as the version being installed. Adds an e2e test proving the guard works.

The npm path and PATH env setup was duplicated between list_global_packages and reinstall_packages.

Also adds a clarifying comment on the scoped package '@' filter logic.

Extracts the multi-assertion output verification into a helper function with shell-specific implementations for Bash/Zsh, Fish, and PowerShell.

Follow up on --reinstall-packages-from by listing global packages from the installed Node directory instead of calling npm ls. This avoids npm output and exit-code quirks while preserving behavior for scoped packages and npm/corepack filtering.

Ignore symlinked entries when scanning global packages for --reinstall-packages-from and log a warning for skipped items. This avoids trying to reinstall locally linked packages that may not exist in registries.

Windows global npm packages may live under %APPDATA%\npm\node_modules. Scan that location in addition to the Node installation path so --reinstall-packages-from consistently finds and reinstalls globals in Windows CI.

Add a Windows-specific discovery path for --reinstall-packages-from using npm ls --global --depth=0 --json, with an inline rationale that npm prefix location is not reliably derivable from fnm install paths. Keep filesystem scanning for non-Windows platforms.

Keep a single changeset for this PR by folding follow-up filesystem discovery, symlink handling, and Windows package discovery notes into the original reinstall-packages-from entry.

Copilot AI review requested due to automatic review settings February 12, 2026 18:47

Copilot started reviewing on behalf of amanthanvi February 12, 2026 18:48 View session

Copilot AI reviewed Feb 12, 2026

View reviewed changes

Comment thread e2e/reinstall-packages-from.test.ts Outdated

Schniz added 8 commits April 17, 2026 18:32

Merge branch 'master' into feat/reinstall-packages-from

4171c5d

fix: skip reinstall-packages-from when source and target versions are…

2c3fad3

… the same Avoids a wasteful no-op reinstall cycle when a user passes the same version to --reinstall-packages-from as the version being installed. Adds an e2e test proving the guard works.

refactor: extract npm_env_for_version helper to reduce duplication

6eecf2e

The npm path and PATH env setup was duplicated between list_global_packages and reinstall_packages.

fix: add Send + Sync bounds to ReinstallPackagesError source

5705657

fix: warn when npm ls exits non-zero with partial output

90f28ee

Also adds a clarifying comment on the scoped package '@' filter logic.

test: expand reinstall-packages-from e2e tests to cover Zsh and Fish

734650a

Extracts the multi-assertion output verification into a helper function with shell-specific implementations for Bash/Zsh, Fish, and PowerShell.

fix: skip symlinked globals in package reinstallation

9644e46

Ignore symlinked entries when scanning global packages for --reinstall-packages-from and log a warning for skipped items. This avoids trying to reinstall locally linked packages that may not exist in registries.

vercel Bot deployed to Preview April 18, 2026 01:29 View deployment

fix: include APPDATA npm globals in reinstall scan

6f10b8b

Windows global npm packages may live under %APPDATA%\npm\node_modules. Scan that location in addition to the Node installation path so --reinstall-packages-from consistently finds and reinstalls globals in Windows CI.

vercel Bot deployed to Preview April 19, 2026 01:26 View deployment

vercel Bot deployed to Preview April 19, 2026 01:34 View deployment

chore: consolidate reinstall-packages changesets

32789c1

Keep a single changeset for this PR by folding follow-up filesystem discovery, symlink handling, and Windows package discovery notes into the original reinstall-packages-from entry.

vercel Bot deployed to Preview April 19, 2026 01:35 View deployment

fix: stabilize reinstall CI checks across platforms

f3c174f

vercel Bot deployed to Preview April 19, 2026 02:31 View deployment

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feat: add --reinstall-packages-from flag to fnm install#1505

feat: add --reinstall-packages-from flag to fnm install#1505
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amanthanvi commented Feb 12, 2026

Summary

Motivation

Implementation

Package listing (source version)

Package installation (target version)

Error handling

Cross-platform

Usage

Testing

Checklist

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