dagger.#Nop: work around bugs in the DAG resolver

Signed-off-by: Solomon Hykes <solomon@dagger.io>

pkg/dagger.io/dagger/nop.cue

@@ -0,0 +1,10 @@
+package dagger
+
+// A core action that does nothing
+// Useful to work around bugs in the DAG resolver.
+//  See for example https://github.com/dagger/dagger/issues/1789
+#Nop: {
+	$dagger: task: _name: "Nop"
+	input:  _
+	output: input
+}

plan/task/nop.go

@@ -0,0 +1,20 @@
+package task
+
+import (
+	"context"
+
+	"go.dagger.io/dagger/compiler"
+	"go.dagger.io/dagger/plancontext"
+	"go.dagger.io/dagger/solver"
+)
+
+func init() {
+	Register("Nop", func() Task { return &nopTask{} })
+}
+
+type nopTask struct {
+}
+
+func (t *nopTask) Run(ctx context.Context, pctx *plancontext.Context, s solver.Solver, v *compiler.Value) (*compiler.Value, error) {
+	return v, nil
+}