feat(internal/librarian/ruby): support installing Ruby gem dependencies

internal/librarian/librarian.go

@@ -30,6 +30,7 @@ import (
 	"github.com/googleapis/librarian/internal/librarian/nodejs"
 	"github.com/googleapis/librarian/internal/librarian/php"
 	"github.com/googleapis/librarian/internal/librarian/python"
+	"github.com/googleapis/librarian/internal/librarian/ruby"
 	"github.com/googleapis/librarian/internal/librarian/rust"
 	"github.com/googleapis/librarian/internal/tool/protoc"
 	"github.com/googleapis/librarian/internal/yaml"
@@ -123,6 +124,8 @@ Examples:
 				return php.Install(ctx, tools)
 			case config.LanguagePython:
 				return python.Install(ctx)
+			case config.LanguageRuby:
+				return ruby.Install(ctx, tools)
 			case config.LanguageRust:
 				return rust.Install(ctx, tools)
 			default:

internal/librarian/ruby/install.go

@@ -15,14 +15,36 @@
 package ruby
 
 import (
+	"errors"
 	"fmt"
+	"os/exec"
 	"path/filepath"
 
+	"context"
+
 	"github.com/googleapis/librarian/internal/cache"
+	"github.com/googleapis/librarian/internal/config"
+	"github.com/googleapis/librarian/internal/tool/gem"
 )
 
 const toolsDir = "ruby_tools"
 
+var (
+	errNoGems            = errors.New("no gem tools specified")
+	errMissingExecutable = errors.New("is not installed or not in PATH, which is required for Ruby tool installation")
+)
+
+// Install installs Ruby gem dependencies.
+func Install(ctx context.Context, tools *config.Tools) error {
+	if err := verify(tools); err != nil {
+		return err
+	}
+	if err := gem.Install(ctx, tools.Gem); err != nil {
+		return err
+	}
+	return nil
+}
+
 // InstallDir gets the directory where tools should be installed.
 func InstallDir() (string, error) {
 	dir, err := cache.BinDirectory()
@@ -44,3 +66,16 @@ func binDir() (string, error) {
 	}
 	return filepath.Join(installDir, "bin"), nil
 }
+
+func verify(tools *config.Tools) error {
+	if tools == nil || len(tools.Gem) == 0 {
+		return errNoGems
+	}
+
+	for _, cmd := range []string{"gem"} {
+		if _, err := exec.LookPath(cmd); err != nil {
+			return fmt.Errorf("%s %w: %w", cmd, errMissingExecutable, err)
+		}
+	}
+	return nil
+}

internal/librarian/ruby/install_test.go

@@ -15,10 +15,45 @@
 package ruby
 
 import (
+	"bytes"
+	"errors"
+	"os"
 	"path/filepath"
 	"testing"
+
+	"github.com/googleapis/librarian/internal/config"
 )
 
+func TestInstall(t *testing.T) {
+	stubDir := t.TempDir()
+	gemStubPath := filepath.Join(stubDir, "gem")
+	recordFile := filepath.Join(t.TempDir(), "calls.txt")
+	stubContent := "#!/bin/sh\necho \"$*\" >> \"" + recordFile + "\"\nexit 0\n"
+	if err := os.WriteFile(gemStubPath, []byte(stubContent), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv("PATH", stubDir+string(filepath.ListSeparator)+os.Getenv("PATH"))
+	tools := &config.Tools{
+		Gem: []*config.GemTool{
+			{
+				Name:    "gapic-generator",
+				Version: "1.2.3",
+			},
+		},
+	}
+	if err := Install(t.Context(), tools); err != nil {
+		t.Fatalf("Install() returned unexpected error: %v", err)
+	}
+	data, err := os.ReadFile(recordFile)
+	if err != nil {
+		t.Fatalf("failed to read call records: %v", err)
+	}
+	want := []byte("install gapic-generator -v 1.2.3 --no-document\n")
+	if !bytes.Equal(data, want) {
+		t.Errorf("gem called with = %q, want %q", data, want)
+	}
+}
+
 func TestInstallDir(t *testing.T) {
 	binDir := t.TempDir()
 	t.Setenv("LIBRARIAN_BIN", binDir)
@@ -44,3 +79,71 @@ func TestBinDir(t *testing.T) {
 		t.Errorf("binDir() = %q, want %q", got, want)
 	}
 }
+
+func TestVerify(t *testing.T) {
+	stubDir := t.TempDir()
+	gemStubPath := filepath.Join(stubDir, "gem")
+	// Create a simple shell script stub for "gem".
+	stubContent := "#!/bin/sh\nexit 0\n"
+	if err := os.WriteFile(gemStubPath, []byte(stubContent), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv("PATH", stubDir+string(filepath.ListSeparator)+os.Getenv("PATH"))
+	tools := &config.Tools{
+		Gem: []*config.GemTool{
+			{
+				Name:    "a-gem-tool",
+				Version: "1.0",
+			},
+		},
+	}
+
+	if err := verify(tools); err != nil {
+		t.Errorf("verify() returned unexpected error: %v", err)
+	}
+}
+
+func TestVerify_Error(t *testing.T) {
+	for _, test := range []struct {
+		name    string
+		tools   *config.Tools
+		setup   func(t *testing.T)
+		wantErr error
+	}{
+		{
+			name:    "nil tools",
+			tools:   nil,
+			wantErr: errNoGems,
+		},
+		{
+			name:    "empty tools",
+			tools:   &config.Tools{},
+			wantErr: errNoGems,
+		},
+		{
+			name: "missing gem in path",
+			tools: &config.Tools{
+				Gem: []*config.GemTool{
+					{
+						Name:    "a-gem-tool",
+						Version: "1.0",
+					},
+				},
+			},
+			setup: func(t *testing.T) {
+				t.Setenv("PATH", t.TempDir())
+			},
+			wantErr: errMissingExecutable,
+		},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			if test.setup != nil {
+				test.setup(t)
+			}
+			err := verify(test.tools)
+			if !errors.Is(err, test.wantErr) {
+				t.Fatalf("verify() error = %v, wantErr = %v", err, test.wantErr)
+			}
+		})
+	}
+}