CHEF-34003: Support ~/.chef/ruby/<version>/gems for Habitat gem persistence

[sanghinitin]

Summary

• What changed: Modified the chef gem command to use ~/.chef/ruby/<ruby_version>/gems as the default GEM_HOME when running inside a Habitat-based Workstation environment. This ensures user-installed gems persist across Workstation package upgrades (previously lost when /hab/pkgs/... path changed on each upgrade).
• Why: Gems installed via chef gem install were being lost on every Workstation upgrade because the Habitat package path changes. This aligns Habitat behavior with the existing omnibus approach that already uses Gem.user_dir.
• Plan: CHEF-34003 — Gem extension support for Workstation 26
• Files/paths touched:
  • lib/chef-cli/command/gem.rb — Added setup_gem_environment for Habitat detection
  • lib/chef-cli/helpers.rb — Added habitat_user_gem_dir, updated habitat_env
  • habitat/plan.sh — Updated wrapper script for runtime GEM_HOME/GEM_PATH resolution; added bundle config unset with
  • habitat/plan.ps1 — Added CHEF_GEM_HOME_ENABLED runtime env marker
  • binstub_patch.rb — Prepends user gem dir to GEM_PATH in all binstubs
  • spec/unit/command/gem_spec.rb — New spec (15 examples)
  • spec/unit/helpers_spec.rb — Updated habitat env tests

Evidence

• Tests:

  bundle exec rspec spec/unit/command/gem_spec.rb spec/unit/helpers_spec.rb
  20 examples, 0 failures
  

• Coverage: 88.73% line coverage (126/142 lines)
• Style: bundle exec cookstyle lib/chef-cli/command/gem.rb spec/unit/command/gem_spec.rb → 0 offenses

Risk & Rollback

• Risk: Low — changes are gated by habitat_install? check; non-Habitat installs are completely unaffected
• Rollback: git revert 49d250a8 or remove the setup_gem_environment call in gem.rb

Review Focus

• Verify the habitat_user_gem_dir path convention (~/.chef/ruby/<version>/gems) aligns with team expectations
• Confirm plan.sh wrapper correctly resolves Ruby ABI version at runtime
• Ensure binstub_patch.rb change does not break appbundler-generated binstubs in omnibus installs (gated by unless ENV["APPBUNDLER_ALLOW_RVM"])
• Verification steps:

  bundle exec rspec spec/unit/command/gem_spec.rb spec/unit/helpers_spec.rb
  bundle exec cookstyle lib/chef-cli/command/gem.rb spec/unit/command/gem_spec.rb

Test Cases Run With Evidence

Test	Result
Non-Habitat: GemForwarder forwards params without modifying GEM_HOME	PASS
Habitat: GemForwarder sets GEM_HOME to ~/.chef/ruby//gems	PASS
Habitat: GEM_PATH includes both user dir and vendor dir	PASS
Habitat: Creates gem directory if missing	PASS
Habitat: Skips mkdir if directory exists	PASS
Habitat: All gem subcommands (install/list/uninstall/source/search/update) forwarded	PASS
Habitat: Gem.clear_paths called after env setup	PASS
SystemExitException: exits with correct code	PASS
habitat_user_gem_dir: returns version-specific path	PASS
helpers habitat_env: GEM_HOME set to user gem dir	PASS
helpers habitat_env: GEM_PATH includes user dir + vendor	PASS

[github-actions]

Simplecov Report

Covered	Threshold
98.51%	90%