@@ -227,27 +227,28 @@ func from(b *Builder, args []string, attributes map[string]bool, original string

 		return err

 	}

-	// Windows cannot support a container with no base image.

-	if name == api.NoBaseImageSpecifier {

-		if runtime.GOOS == "windows" {

-			return errors.New("Windows does not support FROM scratch")

+	if im, ok := b.imageContexts.byName[name]; ok {

+		if len(im.ImageID()) > 0 {

+			image = im

 		}

-		b.image = ""

-		b.noBaseImage = true

 	} else {

-		// TODO: don't use `name`, instead resolve it to a digest

-		if !b.options.PullParent {

-			image, _ = b.docker.GetImageOnBuild(name)

-			// TODO: shouldn't we error out if error is different from "not found" ?

-		}

-		if image == nil {

+		// Windows cannot support a container with no base image.

+		if name == api.NoBaseImageSpecifier {

+			if runtime.GOOS == "windows" {

+				return errors.New("Windows does not support FROM scratch")

+			}

+			b.image = ""

+			b.noBaseImage = true

+		} else {

 			var err error

-			image, err = b.docker.PullOnBuild(b.clientCtx, name, b.options.AuthConfigs, b.Output)

+			image, err = pullOrGetImage(b, name)

 			if err != nil {

 				return err

 			}

 		}

-		b.imageContexts.update(image.ImageID())

+	}

+	if image != nil {

+		b.imageContexts.update(image.ImageID(), image.RunConfig())

 	}

 	b.from = image

@@ -838,9 +839,23 @@ func getShell(c *container.Config) []string {

 // mountByRef creates an imageMount from a reference. pulling the image if needed.

 func mountByRef(b *Builder, name string) (*imageMount, error) {

+	image, err := pullOrGetImage(b, name)

+	if err != nil {

+		return nil, err

+	}

+	im, err := b.imageContexts.new("", false)

+	if err != nil {

+		return nil, err

+	}

+	im.id = image.ImageID()

+	return im, nil

+}

+

+func pullOrGetImage(b *Builder, name string) (builder.Image, error) {

 	var image builder.Image

 	if !b.options.PullParent {

 		image, _ = b.docker.GetImageOnBuild(name)

+		// TODO: shouldn't we error out if error is different from "not found" ?

 	}

 	if image == nil {

 		var err error

@@ -849,10 +864,5 @@ func mountByRef(b *Builder, name string) (*imageMount, error) {

 			return nil, err

 		}

 	}

-	im, err := b.imageContexts.new("", false)

-	if err != nil {

-		return nil, err

-	}

-	im.id = image.ImageID()

-	return im, nil

+	return image, nil

 }

@@ -6,6 +6,7 @@ import (

 	"sync"

 	"github.com/Sirupsen/logrus"

+	"github.com/docker/docker/api/types/container"

 	"github.com/docker/docker/builder"

 	"github.com/docker/docker/builder/remotecontext"

 	"github.com/pkg/errors"

@@ -37,8 +38,9 @@ func (ic *imageContexts) new(name string, increment bool) (*imageMount, error) {

 	return im, nil

 }

-func (ic *imageContexts) update(imageID string) {

+func (ic *imageContexts) update(imageID string, runConfig *container.Config) {

 	ic.list[len(ic.list)-1].id = imageID

+	ic.list[len(ic.list)-1].runConfig = runConfig

 }

 func (ic *imageContexts) validate(i int) error {

@@ -105,10 +107,11 @@ func (ic *imageContexts) setCache(id, path string, v interface{}) {

 // imageMount is a reference for getting access to a buildcontext that is backed

 // by an existing image

 type imageMount struct {

-	id      string

-	ctx     builder.Context

-	release func() error

-	ic      *imageContexts

+	id        string

+	ctx       builder.Context

+	release   func() error

+	ic        *imageContexts

+	runConfig *container.Config

 }

 func (im *imageMount) context() (builder.Context, error) {

@@ -140,6 +143,13 @@ func (im *imageMount) unmount() error {

 	return nil

 }

+func (im *imageMount) ImageID() string {

+	return im.id

+}

+func (im *imageMount) RunConfig() *container.Config {

+	return im.runConfig

+}

+

 type pathCache struct {

 	mu    sync.Mutex

 	items map[string]interface{}

@@ -85,7 +85,7 @@ func (b *Builder) commit(id string, autoCmd strslice.StrSlice, comment string) e

 	}

 	b.image = imageID

-	b.imageContexts.update(imageID)

+	b.imageContexts.update(imageID, &autoConfig)

 	return nil

 }

@@ -497,7 +497,7 @@ func (b *Builder) probeCache() (bool, error) {

 	fmt.Fprint(b.Stdout, " ---> Using cache\n")

 	logrus.Debugf("[BUILDER] Use cached version: %s", b.runConfig.Cmd)

 	b.image = string(cache)

-	b.imageContexts.update(b.image)

+	b.imageContexts.update(b.image, b.runConfig)

 	return true, nil

 }

@@ -5941,6 +5941,67 @@ func (s *DockerSuite) TestBuildCopyFromImplicitFrom(c *check.C) {

 	}

 }

+func (s *DockerRegistrySuite) TestBuildCopyFromImplicitPullingFrom(c *check.C) {

+	repoName := fmt.Sprintf("%v/dockercli/testf", privateRegistryURL)

+

+	dockerfile := `

+		FROM busybox

+		COPY foo bar`

+	ctx := fakeContext(c, dockerfile, map[string]string{

+		"Dockerfile": dockerfile,

+		"foo":        "abc",

+	})

+	defer ctx.Close()

+

+	result := buildImage(repoName, withExternalBuildContext(ctx))

+	result.Assert(c, icmd.Success)

+

+	dockerCmd(c, "push", repoName)

+	dockerCmd(c, "rmi", repoName)

+

+	dockerfile = `

+		FROM busybox

+		COPY --from=%s bar baz`

+

+	ctx = fakeContext(c, fmt.Sprintf(dockerfile, repoName), map[string]string{

+		"Dockerfile": dockerfile,

+	})

+	defer ctx.Close()

+

+	result = buildImage("build1", withExternalBuildContext(ctx))

+	result.Assert(c, icmd.Success)

+

+	dockerCmdWithResult("run", "build1", "cat", "baz").Assert(c, icmd.Expected{Out: "abc"})

+}

+

+func (s *DockerSuite) TestBuildFromPreviousBlock(c *check.C) {

+	dockerfile := `

+		FROM busybox as foo

+		COPY foo /

+		FROM foo as foo1

+		RUN echo 1 >> foo

+		FROM foo as foO2

+		RUN echo 2 >> foo

+		FROM foo

+		COPY --from=foo1 foo f1

+		COPY --from=FOo2 foo f2

+		` // foo2 case also tests that names are canse insensitive

+	ctx := fakeContext(c, dockerfile, map[string]string{

+		"Dockerfile": dockerfile,

+		"foo":        "bar",

+	})

+	defer ctx.Close()

+

+	result := buildImage("build1", withExternalBuildContext(ctx))

+	result.Assert(c, icmd.Success)

+

+	dockerCmdWithResult("run", "build1", "cat", "foo").Assert(c, icmd.Expected{Out: "bar"})

+

+	dockerCmdWithResult("run", "build1", "cat", "f1").Assert(c, icmd.Expected{Out: "bar1"})

+

+	dockerCmdWithResult("run", "build1", "cat", "f2").Assert(c, icmd.Expected{Out: "bar2"})

+}

+

 // TestBuildOpaqueDirectory tests that a build succeeds which

 // creates opaque directories.

 // See https://github.com/docker/docker/issues/25244