GeezerVison

LLM Description written by Claude Code:claude-opus-5-5

Fixes #1295

Summary

After a team migrates to v5 as documented, every other checkout that ran bundle install under v4 (teammates' machines, persistent CI runners) still has Bundler's plugin registration for socket-patch, pointing at the deleted .socket/bundler-plugin/. On Bundler 2.3–2.5 every bundle install then fails with a LoadError that doesn't mention socket-patch. 2.6+ prints a warning on every run.

This PR:

• Detects it. scan (gem ecosystem selected, project mode) and apply (gem patches in scope, project mode) read $BUNDLE_APP_CONFIG/plugin/index (default .bundle/plugin/index). If it registers socket-patch at a path that no longer exists, they report a gem_bundler_plugin_stale run warning. The detail names the path, the index file and the one-line fix (bundle plugin uninstall socket-patch, or delete .bundle/plugin/). Under --json it goes in warnings[]; otherwise it prints one Warning: line on stderr, and apply suppresses it under --silent. A registration whose directory still exists is a working v4 setup and is not reported.
• Documents the per-checkout step in docs/migrating-to-v5.md, in CLI_CONTRACT.md (the "Agent mode in CI" section, which never mentioned it before), and in the retired-setup usage error.

Root cause

v4's setup --remove cleared .bundle/plugin/index (#210). v5 removed setup (#279), and .bundle/ is never committed, so nothing removes the registration in the checkouts that weren't the migrator's.

Evidence

• Reproduced locally with Bundler 4.0.18 / Ruby 3.3.6. After bundle install with a v4-style plugin "socket-patch", path: ".socket/bundler-plugin" block, the index reads plugin_paths:\n socket-patch: "<abs>/.socket/bundler-plugin". After removing the block and the directory, every bundle install prints "The following plugin paths don't exist…". bundle plugin uninstall socket-patch empties the index and clears the warning. The unit-test fixture uses that exact index text.
• Red → green: cargo test -p socket-patch-cli --all-features --test apply -- gem_stale_bundler_plugin
  • without the scan/apply wiring: scan_json_warns_about_stale_plugin_registration FAILED and apply_warns_about_stale_plugin_registration FAILED; scan_json_is_quiet_while_the_plugin_dir_exists passed
  • with the fix: all 3 pass, and the existing in_process_gem_config_warning tests still pass
• cargo test -p socket-patch-core --lib: the 3 new tests (registered_plugin_path_reads_bundlers_index, stale_plugin_registration_is_reported, stale_plugin_registration_follows_bundle_app_config) pass. Full lib run: 6094 passed. The 4 failures are pre-existing permission tests (copy_tree, vlt_heal, pypi_poetry, pypi_requirements) that can't fail as intended because the sandbox runs as uid 0, which bypasses read-only permissions. They're unrelated to this diff.
• cargo test -p socket-patch-cli --all-features --lib: 915 passed. --test cli_parse_main setup_subcommand_is_removed passes; it now also asserts that the error names bundle plugin uninstall socket-patch.
• cargo clippy --workspace --all-features -- -D warnings is clean, and rustfmt is clean on every touched file.
• A full cargo test --workspace does not fit in this sandbox's disk allowance (ENOSPC while linking the test binaries), so CI runs the full matrix.

Per-issue checklist

• v5 Bundler plugin cleanup leaves .bundle/plugin registered in every other checkout, so bundle install crashes with LoadError on Bundler 2.3–2.5 #1295, detection: gem_stale_bundler_plugin::{scan_json_warns_about_stale_plugin_registration, apply_warns_about_stale_plugin_registration, scan_json_is_quiet_while_the_plugin_dir_exists}, plus the core unit tests
• v5 Bundler plugin cleanup leaves .bundle/plugin registered in every other checkout, so bundle install crashes with LoadError on Bundler 2.3–2.5 #1295, docs and setup error: cli_parse_main::setup_subcommand_is_removed

Notes

• Wrappers (npm/, pypi/, gem/) carry no Bundler plugin cleanup text, so they need no changes.
• No CHANGELOG.md changes, per AGENTS.md.

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https://claude.ai/code/session_01NBZNtzNwEeuo5izMsyMaGm

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