Add `--no-build-extension` and `--no-install-plugin` options to gem install by hsbt · Pull Request #9473 · ruby/rubygems

hsbt · 2026-04-10T06:25:06Z

Background

Installing a gem can execute arbitrary code through two mechanisms: native extension builds (via extconf.rb, Rakefile, etc.) and plugin evaluation (via rubygems_plugin.rb). This is a known supply chain attack vector, analogous to npm's postinstall scripts.

This PR adds --no-build-extension and --no-install-plugin options to gem install, allowing users to opt out of these behaviors. Bundler also gains corresponding no_build_extension and no_install_plugin configuration settings.

When extensions or plugins are skipped, a warning message is displayed with recovery instructions pointing to gem pristine --extensions or gem pristine --only-plugins, so users can re-enable them later without reinstalling the gem.

These options only take effect when explicitly specified by the user. The default behavior remains unchanged: extensions are built and plugins are installed as before.

Making --no-build-extension the default would be a significant behavioral change that requires careful investigation into how many gems in the ecosystem rely on native extensions being built at install time, how tools like bundler and CI pipelines depend on this behavior, and what the migration path would look like for gem authors.

That analysis is outside the scope of this PR.

Make sure the following tasks are checked

Describe the problem / feature
Write tests for features and bug fixes
Write code to solve the problem
Make sure you follow the current code style and write meaningful commit messages without tags

Copilot

Pull request overview

This PR adds opt-out controls to RubyGems and Bundler to reduce supply-chain risk during installation by allowing users to skip native extension builds and RubyGems plugin installation/loading when explicitly requested.

Changes:

Add --[no-]build-extension and --[no-]install-plugin options to RubyGems install/update option parsing and propagate them through dependency installation.
Update Gem::Installer (and Bundler’s RubyGems installer wrapper) to conditionally skip extension builds and plugin installation/loading, with warnings and recovery guidance.
Add test coverage in RubyGems (Minitest) and Bundler (RSpec) for no_build_extension.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
test/rubygems/test_gem_installer.rb	Adds RubyGems installer tests for skipping extension builds and plugin installation/loading.
spec/install/gems/no_build_extension_spec.rb	Adds Bundler spec verifying `no_build_extension` prevents extension build artifacts.
lib/rubygems/request_set.rb	Skips rebuilding extensions for already-installed specs when `:build_extension == false`.
lib/rubygems/installer.rb	Gates extension builds, plugin generation, and plugin loading; adds warning helpers; avoids loading missing plugin wrappers.
lib/rubygems/install_update_options.rb	Defines the new CLI flags for install/update commands.
lib/rubygems/dependency_installer.rb	Stores and forwards new options into the request set install flow.
bundler/lib/bundler/source/rubygems.rb	Passes Bundler settings (`no_build_extension`, `no_install_plugin`) into RubyGems installer options.
bundler/lib/bundler/source/path/installer.rb	Skips building extensions for path installs when `no_build_extension` is set.
bundler/lib/bundler/settings.rb	Registers `no_build_extension` and `no_install_plugin` as boolean settings.
bundler/lib/bundler/rubygems_gem_installer.rb	Mirrors RubyGems installer gating behavior for Bundler’s installer wrapper.

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lib/rubygems/installer.rb

+    if options[:build_extension] == false
+      warn_skipped_extensions
+    else
+      build_extensions
+    end


bundler/lib/bundler/source/rubygems.rb

            wrappers: true,
            env_shebang: true,
            build_args: options[:build_args],
-            bundler_extension_cache_path: extension_cache_path(spec)
+            bundler_extension_cache_path: extension_cache_path(spec),
+            build_extension: Bundler.settings[:no_build_extension] ? false : nil,
+            install_plugin: Bundler.settings[:no_install_plugin] ? false : nil


lib/rubygems/request_set.rb

    sorted_requests.each do |req|
      if req.installed? && @always_install.none? {|spec| spec == req.spec.spec }
-        req.spec.spec.build_extensions
+        req.spec.spec.build_extensions unless options[:build_extension] == false
        yield req, nil if block_given?


lib/rubygems/installer.rb

    generate_bin
-    generate_plugins
+    if options[:install_plugin] == false
+      warn_skipped_plugins
+    else
+      generate_plugins
+    end


bundler/lib/bundler/rubygems_gem_installer.rb

+      if options[:install_plugin] == false
+        warn_skipped_plugins
+      else
+        generate_plugins
+      end


…nstall These options allow users to opt out of building native extensions and installing plugins during gem installation, providing an equivalent to npm's --ignore-scripts for mitigating arbitrary code execution vectors. Both options default to true to maintain backward compatibility. Users can disable them per-command or globally via gemrc configuration. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

When plugins are not installed (e.g. via --no-install-plugin), the plugin files do not exist on disk. Without this check, load_plugin would attempt to load non-existent files and produce spurious LoadError warnings. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Extend the --no-build-extension and --no-install-plugin support to Bundler's installation paths. RubyGemsGemInstaller#install now respects these options, and the settings are propagated from Bundler::Settings through Source::RubyGems to the installer. Path::Installer also respects no_build_extension for git/path sources. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

…lugins When extensions or plugins are skipped via --no-build-extension or --no-install-plugin, warn the user and point them to the appropriate gem pristine command to re-enable later. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Without this change, reinstalling or upgrading a gem with --no-install-plugin would still execute a pre-existing plugin wrapper left by a previous install via load_plugin. This defeats the opt-out. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

…config The quality spec requires all Bundler settings to be documented in the bundle-config man page. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

When a gem upgrades from a version with plugins to one without, generate_plugins normally removes the old wrapper files. Skipping generate_plugins entirely with --no-install-plugin prevented this cleanup, leaving stale wrappers that would still be loaded. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Edouard-chin · 2026-04-13T14:46:48Z

bundler/lib/bundler/man/bundle-config.1

 Whether Bundler should include a checksums section in new lockfiles, to protect from compromised gem sources\. Defaults to true\.
 .TP
+\fBno_build_extension\fR (\fBBUNDLE_NO_BUILD_EXTENSION\fR)
+Whether Bundler should skip building native extensions during installation\. When set, gems are installed without compiling their C extensions\. To build extensions later, run \fBgem pristine <gem> \-\-extensions\fR\.


I think the gem pristine <gem> command is not going to work if a user has set BUNDLE_PATH (either in env or config). Wouldn't running bundle install again build the extensions ?

hsbt added rubygems: feature bundler: feature labels Apr 10, 2026

Copilot AI review requested due to automatic review settings April 10, 2026 06:25

Copilot started reviewing on behalf of hsbt April 10, 2026 06:25 View session

Copilot AI reviewed Apr 10, 2026

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hsbt and others added 9 commits April 13, 2026 09:04

Document no_build_extension and no_install_plugin settings in bundle-…

3589a8b

…config The quality spec requires all Bundler settings to be documented in the bundle-config man page. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Add Bundler spec for no_install_plugin setting

24b00a1

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Add no_build_extension and no_install_plugin specs to windows_tag_group

939287d

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hsbt force-pushed the ignore-scripts branch from 327b53a to 939287d Compare April 13, 2026 00:40

Edouard-chin reviewed Apr 13, 2026

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Add `--no-build-extension` and `--no-install-plugin` options to gem install#9473

Add `--no-build-extension` and `--no-install-plugin` options to gem install#9473
hsbt wants to merge 9 commits intomasterfrom
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Edouard-chin Apr 13, 2026 •

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hsbt commented Apr 10, 2026

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Edouard-chin Apr 13, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Edouard-chin Apr 13, 2026 •

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