Add credential helper support for bundler

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

@@ -113,6 +113,8 @@ The following is a list of all configuration keys and their purpose\. You can le
 .IP "\(bu" 4
 \fBconsole\fR (\fBBUNDLE_CONSOLE\fR): The console that \fBbundle console\fR starts\. Defaults to \fBirb\fR\.
 .IP "\(bu" 4
+\fBcredential\.helper\fR (\fBBUNDLE_CREDENTIAL_HELPER\fR): The path to a credential helper to use for fetching credentials from a remote gem server\.
+.IP "\(bu" 4
 \fBdefault_install_uses_path\fR (\fBBUNDLE_DEFAULT_INSTALL_USES_PATH\fR): Whether a \fBbundle install\fR without an explicit \fB\-\-path\fR argument defaults to installing gems in \fB\.bundle\fR\.
 .IP "\(bu" 4
 \fBdeployment\fR (\fBBUNDLE_DEPLOYMENT\fR): Disallow changes to the \fBGemfile\fR\. When the \fBGemfile\fR is changed and the lockfile has not been updated, running Bundler commands will be blocked\.

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

@@ -166,6 +166,9 @@ learn more about their operation in [bundle install(1)](bundle-install.1.html).
    `bundle install`.
 * `console` (`BUNDLE_CONSOLE`):
    The console that `bundle console` starts. Defaults to `irb`.
+* `credential.helper` (`BUNDLE_CREDENTIAL_HELPER`):
+   The path to a credential helper to use for fetching credentials from a
+   remote gem server.
 * `default_install_uses_path` (`BUNDLE_DEFAULT_INSTALL_USES_PATH`):
    Whether a `bundle install` without an explicit `--path` argument defaults
    to installing gems in `.bundle`.

bundler/lib/bundler/settings.rb

@@ -89,6 +89,7 @@ class Settings
       system_bindir
       trust-policy
       version
+      credential.helper
     ].freeze
 
     DEFAULT_CONFIG = {
@@ -197,7 +198,7 @@ def mirror_for(uri)
     end
 
     def credentials_for(uri)
-      self[uri.to_s] || self[uri.host]
+      credentials_from_helper(uri) || self[uri.to_s] || self[uri.host]
     end
 
     def gem_mirrors
@@ -595,5 +596,35 @@ def self.key_to_s(key)
         end
       end
     end
+
+    def credentials_from_helper(uri)
+      helper_key = "credential.helper.#{uri.host}"
+      helper_path = self[helper_key]
+      return unless helper_path
+
+      begin
+        require "shellwords"
+        command = Shellwords.shellsplit(helper_path)
+        command[0] = if command[0].start_with?("/", "~")
+          command[0]
+        else
+          "bundler-credential-#{command[0]}"
+        end
+
+        output = Bundler.with_unbundled_env { IO.popen(command, &:read) }
+        unless Process.last_status.success?
+          Bundler.ui.warn "Credential helper failed with exit status #{$?.exitstatus}"
+          return nil
+        end
+        output = output.to_s.strip
+        output.empty? ? nil : output
+      rescue Errno::ENOENT, ArgumentError => e
+        Bundler.ui.warn "Credential helper #{helper_path} not available: #{e.message}"
+        nil
+      rescue StandardError => e
+        Bundler.ui.warn "Credential helper failed: #{e.message}"
+        nil
+      end
+    end
   end
 end

bundler/spec/bundler/settings_spec.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require "stringio"
 require "bundler/settings"
 
 RSpec.describe Bundler::Settings do
@@ -263,6 +264,47 @@
         expect(settings.credentials_for(uri)).to eq(credentials)
       end
     end
+
+    context "with credential helper configured" do
+      let(:helper_path) { "/path/to/helper" }
+      let(:uri) { Gem::URI("https://gemserver.example.org") }
+
+      before do
+        settings.set_local "credential.helper.gemserver.example.org", helper_path
+        allow(Process).to receive(:last_status).and_return(double(success?: true, exitstatus: 0))
+      end
+
+      it "uses the credential helper when configured" do
+        expect(IO).to receive(:popen).with([helper_path]).and_yield(StringIO.new("username:password\n"))
+        expect(settings.credentials_for(uri)).to eq("username:password")
+      end
+
+      it "fallback to config when helper fails" do
+        expect(IO).to receive(:popen).with([helper_path]).and_raise(StandardError, "Helper failed")
+        expect(Bundler.ui).to receive(:warn).with("Credential helper failed: Helper failed")
+        settings.set_local "gemserver.example.org", "fallback:password"
+        expect(settings.credentials_for(uri)).to eq("fallback:password")
+      end
+
+      it "returns nil when helper fails and no fallback config exists" do
+        expect(IO).to receive(:popen).with([helper_path]).and_yield(StringIO.new(""))
+        expect(settings.credentials_for(uri)).to be_nil
+      end
+
+      context "with relative helper path and options" do
+        let(:helper_path) { "custom-helper --foo=bar" }
+
+        before do
+          settings.set_local "credential.helper.gemserver.example.org", helper_path
+          allow(Process).to receive(:last_status).and_return(double(success?: true, exitstatus: 0))
+        end
+
+        it "prepends bundler-credential- to the helper name" do
+          expect(IO).to receive(:popen).with(["bundler-credential-custom-helper", "--foo=bar"]).and_yield(StringIO.new("username:password\n"))
+          expect(settings.credentials_for(uri)).to eq("username:password")
+        end
+      end
+    end
   end
 
   describe "URI normalization" do