vendoring: support multiple modules

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

pkg/pkg.go

@@ -3,24 +3,112 @@ package pkg
 import (
 	"context"
 	"embed"
+	"errors"
 	"fmt"
 	"io/fs"
 	"os"
 	"path"
 	"path/filepath"
+
+	"github.com/gofrs/flock"
+	"github.com/rs/zerolog/log"
 )
 
 var (
 	// FS contains the filesystem of the stdlib.
-	//go:embed alpha.dagger.io/**/*.cue alpha.dagger.io/**/*/*.cue alpha.dagger.io/europa/dagger/*.cue alpha.dagger.io/europa/dagger/engine/*.cue
+	//go:embed alpha.dagger.io/**/*.cue alpha.dagger.io/**/*/*.cue dagger.io/**/*.cue dagger.io/**/*/*.cue
 	FS embed.FS
-
-	AlphaModule   = "alpha.dagger.io"
-	EnginePackage = fmt.Sprintf("%s/europa/dagger/engine", AlphaModule)
 )
 
-func Vendor(ctx context.Context, dest string) error {
-	// Write the current version
+var (
+	AlphaModule   = "alpha.dagger.io"
+	DaggerModule  = "dagger.io"
+	EnginePackage = fmt.Sprintf("%s/dagger/engine", DaggerModule)
+
+	modules = []string{
+		AlphaModule,
+		DaggerModule,
+	}
+
+	lockFilePath = "dagger.lock"
+)
+
+func Vendor(ctx context.Context, p string) error {
+	if p == "" {
+		p = getCueModParent()
+	}
+
+	cuePkgDir := path.Join(p, "cue.mod", "pkg")
+	if err := os.MkdirAll(cuePkgDir, 0755); err != nil {
+		return err
+	}
+
+	// Lock this function so no more than 1 process can run it at once.
+	lockFile := path.Join(cuePkgDir, lockFilePath)
+	l := flock.New(lockFile)
+	if err := l.Lock(); err != nil {
+		return err
+	}
+	defer func() {
+		l.Unlock()
+		os.Remove(lockFile)
+	}()
+
+	// ensure cue module is initialized
+	if err := cueModInit(ctx, p); err != nil {
+		return err
+	}
+
+	// generate `.gitignore`
+	if err := os.WriteFile(
+		path.Join(cuePkgDir, ".gitignore"),
+		[]byte(fmt.Sprintf("# generated by dagger\n%s\n%s\ndagger.lock\n", AlphaModule, DaggerModule)),
+		0600,
+	); err != nil {
+		return err
+	}
+
+	log.Ctx(ctx).Debug().Str("mod", p).Msg("vendoring packages")
+
+	// Unpack modules in a temporary directory
+	unpackDir, err := os.MkdirTemp(cuePkgDir, "vendor-*")
+	if err != nil {
+		return err
+	}
+	defer os.RemoveAll(unpackDir)
+
+	if err := extractModules(unpackDir); err != nil {
+		return err
+	}
+
+	for _, module := range modules {
+		// Semi-atomic swap of the module
+		//
+		// The following basically does:
+		// $ rm -rf cue.mod/pkg/MODULE.old
+		// $ mv cue.mod/pkg/MODULE cue.mod/pkg/MODULE.old
+		// $ mv VENDOR/MODULE cue.mod/pkg/MODULE
+		// $ rm -rf cue.mod/pkg/MODULE.old
+
+		moduleDir := path.Join(cuePkgDir, module)
+		backupModuleDir := moduleDir + ".old"
+		if err := os.RemoveAll(backupModuleDir); err != nil && !errors.Is(err, os.ErrNotExist) {
+			return err
+		}
+		if err := os.Rename(moduleDir, backupModuleDir); err != nil && !errors.Is(err, os.ErrNotExist) {
+			return err
+		}
+		defer os.RemoveAll(backupModuleDir)
+
+		if err := os.Rename(path.Join(unpackDir, module), moduleDir); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func extractModules(dest string) error {
 	return fs.WalkDir(FS, ".", func(p string, entry fs.DirEntry, err error) error {
 		if err != nil {
 			return err
@@ -48,3 +136,56 @@ func Vendor(ctx context.Context, dest string) error {
 		return os.WriteFile(overlayPath, contents, 0600)
 	})
 }
+
+// getCueModParent traverses the directory tree up through ancestors looking for a cue.mod folder
+func getCueModParent() string {
+	cwd, _ := os.Getwd()
+	parentDir := cwd
+
+	for {
+		if _, err := os.Stat(path.Join(parentDir, "cue.mod")); !errors.Is(err, os.ErrNotExist) {
+			break // found it!
+		}
+
+		parentDir = filepath.Dir(parentDir)
+
+		if parentDir == string(os.PathSeparator) {
+			// reached the root
+			parentDir = cwd // reset to working directory
+			break
+		}
+	}
+
+	return parentDir
+}
+
+func cueModInit(ctx context.Context, parentDir string) error {
+	lg := log.Ctx(ctx)
+
+	modDir := path.Join(parentDir, "cue.mod")
+	modFile := path.Join(modDir, "module.cue")
+	if _, err := os.Stat(modFile); err != nil {
+		if !errors.Is(err, os.ErrNotExist) {
+			return err
+		}
+
+		lg.Debug().Str("mod", parentDir).Msg("initializing cue.mod")
+
+		if err := os.WriteFile(modFile, []byte("module: \"\"\n"), 0600); err != nil {
+			return err
+		}
+	}
+
+	if err := os.Mkdir(path.Join(modDir, "usr"), 0755); err != nil {
+		if !errors.Is(err, os.ErrExist) {
+			return err
+		}
+	}
+	if err := os.Mkdir(path.Join(modDir, "pkg"), 0755); err != nil {
+		if !errors.Is(err, os.ErrExist) {
+			return err
+		}
+	}
+
+	return nil
+}