engine.#Pull implementation

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

plan/task/pull.go

@@ -0,0 +1,79 @@
+package task
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+
+	"cuelang.org/go/cue"
+	"github.com/docker/distribution/reference"
+	"github.com/moby/buildkit/client/llb"
+	"go.dagger.io/dagger/compiler"
+	"go.dagger.io/dagger/plancontext"
+	"go.dagger.io/dagger/solver"
+)
+
+func init() {
+	Register("Pull", func() Task { return &pullTask{} })
+}
+
+type pullTask struct {
+}
+
+func (c *pullTask) Run(ctx context.Context, pctx *plancontext.Context, s solver.Solver, v *compiler.Value) (*compiler.Value, error) {
+	// FIXME: handle auth
+	rawRef, err := v.Lookup("source").String()
+	if err != nil {
+		return nil, err
+	}
+
+	ref, err := reference.ParseNormalizedNamed(rawRef)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse ref %s: %w", rawRef, err)
+	}
+	// Add the default tag "latest" to a reference if it only has a repo name.
+	ref = reference.TagNameOnly(ref)
+
+	st := llb.Image(
+		ref.String(),
+		withCustomName(v, "FetchContainer %s", rawRef),
+	)
+
+	// Load image metadata and convert to to LLB.
+	platform := pctx.Platform.Get()
+	image, digest, err := s.ResolveImageConfig(ctx, ref.String(), llb.ResolveImageConfigOpt{
+		LogName:  vertexNamef(v, "load metadata for %s", ref.String()),
+		Platform: &platform,
+	})
+	if err != nil {
+		return nil, err
+	}
+	imageJSON, err := json.Marshal(image)
+	if err != nil {
+		return nil, err
+	}
+	// Apply Image Config on top of LLB instructions
+	st, err = st.WithImageConfig(imageJSON)
+	if err != nil {
+		return nil, err
+	}
+
+	result, err := s.Solve(ctx, st, pctx.Platform.Get())
+	if err != nil {
+		return nil, err
+	}
+	fs := pctx.FS.New(result)
+
+	out := compiler.NewValue()
+	if err := out.FillPath(cue.ParsePath("output"), fs.MarshalCUE()); err != nil {
+		return nil, err
+	}
+	if err := out.FillPath(cue.ParsePath("digest"), digest.String()); err != nil {
+		return nil, err
+	}
+	if err := out.FillPath(cue.ParsePath("config"), image.Config); err != nil {
+		return nil, err
+	}
+
+	return out, nil
+}

plan/task/util.go

@@ -7,8 +7,12 @@ import (
 	"go.dagger.io/dagger/compiler"
 )
 
-func withCustomName(v *compiler.Value, format string, a ...interface{}) llb.ConstraintsOpt {
+func vertexNamef(v *compiler.Value, format string, a ...interface{}) string {
 	prefix := fmt.Sprintf("@%s@", v.Path().String())
 	name := fmt.Sprintf(format, a...)
-	return llb.WithCustomName(prefix + " " + name)
+	return prefix + " " + name
+}
+
+func withCustomName(v *compiler.Value, format string, a ...interface{}) llb.ConstraintsOpt {
+	return llb.WithCustomName(vertexNamef(v, format, a...))
 }

stdlib/dagger/engine/image.cue

@@ -0,0 +1,45 @@
+package engine
+
+// A ref is an address for a remote container image
+//
+// Examples:
+//   - "index.docker.io/dagger"
+//   - "dagger"
+//   - "index.docker.io/dagger:latest"
+//   - "index.docker.io/dagger:latest@sha256:a89cb097693dd354de598d279c304a1c73ee550fbfff6d9ee515568e0c749cfe"
+#Ref: string
+
+// Container image config
+// See https://opencontainers.org
+// https://github.com/moby/buildkit/blob/master/frontend/dockerfile/dockerfile2llb/image.go
+// https://github.com/opencontainers/image-spec/blob/main/specs-go/v1/config.go
+#ImageConfig: {
+	Env?: [...string]
+	User?: string
+	Cmd?: [...string]
+	...
+}
+
+// Download a container image from a remote repository
+#Pull: {
+	_type: "Pull"
+
+	// Repository source ref
+	source: #Ref
+
+	// Authentication
+	auth: [...{
+		target:   string
+		username: string
+		secret:   string | #Secret
+	}]
+
+	// Root filesystem of downloaded image
+	output: #FS
+
+	// Image digest
+	digest: string
+
+	// Downloaded container image config
+	config: #ImageConfig
+}

tests/tasks.bats

@@ -0,0 +1,10 @@
+setup() {
+    load 'helpers'
+
+    common_setup
+}
+
+@test "task: #Pull" {
+    cd "$TESTDIR"/tasks/pull
+    dagger --europa up
+}

tests/tasks/pull/cue.mod/module.cue

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

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

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

tests/tasks/pull/pull.cue

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"alpha.dagger.io/dagger/engine"
+)
+
+engine.#Plan & {
+	actions: pull: engine.#Pull & {
+		source: "alpine:3.15.0@sha256:e7d88de73db3d3fd9b2d63aa7f447a10fd0220b7cbf39803c803f2af9ba256b3"
+	} & {
+		// assert result
+		digest: "sha256:e7d88de73db3d3fd9b2d63aa7f447a10fd0220b7cbf39803c803f2af9ba256b3"
+		config: {
+			Env: ["PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"]
+			Cmd: ["/bin/sh"]
+		}
+	}
+}