Initial pass at engine.#Scratch - failing

Signed-off-by: Joel Longtine <joel@dagger.io>

plan/task/scratch.go

@@ -0,0 +1,31 @@
+package task
+
+import (
+	"context"
+
+	"github.com/moby/buildkit/client/llb"
+	"go.dagger.io/dagger/compiler"
+	"go.dagger.io/dagger/plancontext"
+	"go.dagger.io/dagger/solver"
+)
+
+func init() {
+	Register("Scratch", func() Task { return &scratchTask{} })
+}
+
+type scratchTask struct {
+}
+
+func (t *scratchTask) Run(ctx context.Context, pctx *plancontext.Context, s solver.Solver, v *compiler.Value) (*compiler.Value, error) {
+	st := llb.Scratch()
+	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(),
+	})
+}

tests/tasks.bats

@@ -88,3 +88,8 @@ setup() {
 
     "$DAGGER" --europa up ./build_auth.cue
 }
+@test "task: #Scratch" {
+    cd "$TESTDIR"/tasks/scratch
+    "$DAGGER" --europa up ./scratch.cue -l debug
+}
+

tests/tasks/scratch/cue.mod/module.cue

@@ -0,0 +1 @@
+module: ""

tests/tasks/scratch/cue.mod/pkg/.gitignore

@@ -0,0 +1,3 @@
+# generated by dagger
+alpha.dagger.io
+dagger.lock

tests/tasks/scratch/scratch.cue

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"alpha.dagger.io/europa/dagger/engine"
+)
+
+engine.#Plan & {
+	actions: {
+		image: engine.#Pull & {
+			source: "alpine:3.15.0@sha256:e7d88de73db3d3fd9b2d63aa7f447a10fd0220b7cbf39803c803f2af9ba256b3"
+		}
+
+		scratch: engine.#Scratch
+
+		exec: engine.#Exec & {
+			input: image.output
+			mounts: fs: {
+				dest:     "/scratch"
+				contents: scratch.output
+			}
+			workdir: "/"
+			args: [
+				"sh", "-c",
+				#"""
+					ls -al
+					"""#,
+			]
+		}
+
+	}
+}