engine.#ReadFile

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

plan/task/readfile.go

@@ -0,0 +1,46 @@
+package task
+
+import (
+	"context"
+	"fmt"
+	"io/fs"
+
+	"cuelang.org/go/cue"
+	"go.dagger.io/dagger/compiler"
+	"go.dagger.io/dagger/plancontext"
+	"go.dagger.io/dagger/solver"
+)
+
+func init() {
+	Register("ReadFile", func() Task { return &readFileTask{} })
+}
+
+type readFileTask struct {
+}
+
+func (t *readFileTask) Run(ctx context.Context, pctx *plancontext.Context, s solver.Solver, v *compiler.Value) (*compiler.Value, error) {
+	path, err := v.Lookup("path").String()
+	if err != nil {
+		return nil, err
+	}
+
+	input, err := pctx.FS.FromValue(v.Lookup("input"))
+	if err != nil {
+		return nil, err
+	}
+	inputFS := solver.NewBuildkitFS(input.Result())
+
+	// FIXME: we should create an intermediate image containing only `path`.
+	// That way, on cache misses, we'll only download the layer with the file contents rather than the entire FS.
+	contents, err := fs.ReadFile(inputFS, path)
+	if err != nil {
+		return nil, fmt.Errorf("ReadFile %s: %w", path, err)
+	}
+
+	output := compiler.NewValue()
+	if err := output.FillPath(cue.ParsePath("contents"), string(contents)); err != nil {
+		return nil, err
+	}
+
+	return output, nil
+}