europa: Code Embedding POC

WIP PoC for code embedding

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

plan/task/source.go

@@ -0,0 +1,101 @@
+package task
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+
+	"github.com/moby/buildkit/client/llb"
+	"github.com/rs/zerolog/log"
+	"go.dagger.io/dagger/compiler"
+	"go.dagger.io/dagger/plancontext"
+	"go.dagger.io/dagger/solver"
+)
+
+func init() {
+	Register("Source", func() Task { return &sourceTask{} })
+}
+
+type sourceTask struct {
+}
+
+func (c *sourceTask) PreRun(ctx context.Context, pctx *plancontext.Context, v *compiler.Value) error {
+	path, err := v.Lookup("path").String()
+	if err != nil {
+		return err
+	}
+
+	if !fs.ValidPath(path) {
+		return fmt.Errorf("invalid path %q", path)
+	}
+
+	absPath, err := v.Lookup("path").AbsPath()
+	if err != nil {
+		return err
+	}
+
+	if _, err := os.Stat(path); errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("path %q does not exist", path)
+	}
+
+	pctx.LocalDirs.Add(absPath)
+
+	return nil
+}
+
+func (c *sourceTask) Run(ctx context.Context, pctx *plancontext.Context, s solver.Solver, v *compiler.Value) (*compiler.Value, error) {
+	lg := log.Ctx(ctx)
+
+	path, err := v.Lookup("path").AbsPath()
+	if err != nil {
+		return nil, err
+	}
+
+	var source struct {
+		Include []string
+		Exclude []string
+	}
+
+	if err := v.Decode(&source); err != nil {
+		return nil, err
+	}
+
+	lg.Debug().Str("path", path).Msg("loading local directory")
+	opts := []llb.LocalOption{
+		withCustomName(v, "Embed %s", path),
+		llb.IncludePatterns(source.Include),
+		llb.ExcludePatterns(source.Exclude),
+		// Without hint, multiple `llb.Local` operations on the
+		// same path get a different digest.
+		llb.SessionID(s.SessionID()),
+		llb.SharedKeyHint(path),
+	}
+
+	// FIXME: Remove the `Copy` and use `Local` directly.
+	//
+	// Copy'ing is a costly operation which should be unnecessary.
+	// However, using llb.Local directly breaks caching sometimes for unknown reasons.
+	st := llb.Scratch().File(
+		llb.Copy(
+			llb.Local(
+				path,
+				opts...,
+			),
+			"/",
+			"/",
+		),
+		withCustomName(v, "Embed %s [copy]", path),
+	)
+
+	result, err := s.Solve(ctx, st, pctx.Platform.Get())
+	if err != nil {
+		return nil, err
+	}
+
+	fs := pctx.FS.New(result)
+	return compiler.NewValue().FillFields(map[string]interface{}{
+		"output": fs.MarshalCUE(),
+	})
+}