Add support for specifying multiple base images to use in the spec

This is pretty much to support building for multiple windows versions
from windowscross but can also be useful for allowing users to specify
something other than a registry reference to provide an image.

The actual support for multiple bases, where it can be supported, will
come in a follow-up commit.

docs/spec.schema.json

@@ -160,6 +160,19 @@
 			"type": "object",
 			"description": "Artifacts describes all the artifacts to include in the package."
 		},
+		"BaseImage": {
+			"properties": {
+				"rootfs": {
+					"$ref": "#/$defs/Source",
+					"description": "Source represents an image rootfs."
+				}
+			},
+			"additionalProperties": false,
+			"type": "object",
+			"required": [
+				"rootfs"
+			]
+		},
 		"BuildStep": {
 			"properties": {
 				"command": {
@@ -487,7 +500,14 @@
 				},
 				"base": {
 					"type": "string",
-					"description": "Base is the base image to use for the output image.\nThis only affects the output image, not the intermediate build image."
+					"description": "Deprecated: Use [Bases] instead."
+				},
+				"Bases": {
+					"items": {
+						"$ref": "#/$defs/BaseImage"
+					},
+					"type": "array",
+					"description": "Bases is used to specify a list of base images to build images for.  The\nintent of allowing multiple bases is for cases, such as Windows, where you\nmay want to publish multiple versions of a base image in one image.\n\nWindows is the example here because of the way Windows works, the image\nthat the base is based off of must match the OS version of the host machine.\nTherefore it is common to have multiple Windows images in one with a\ndifferent value for the os version field of the platform.\n\nFor the most part implementations are not expected to support multiple base\nimages and may error out if multiple are specified.\n\nThis should not be set if [Base] is also set."
 				},
 				"post": {
 					"$ref": "#/$defs/PostInstall",
@@ -500,6 +520,9 @@
 			},
 			"additionalProperties": false,
 			"type": "object",
+			"required": [
+				"Bases"
+			],
 			"description": "ImageConfig is the configuration for the output image."
 		},
 		"PackageConfig": {

frontend/azlinux/handle_container.go

@@ -9,7 +9,6 @@ import (
 	"github.com/Azure/dalec"
 	"github.com/Azure/dalec/frontend"
 	"github.com/moby/buildkit/client/llb"
-	"github.com/moby/buildkit/client/llb/sourceresolver"
 	gwclient "github.com/moby/buildkit/frontend/gateway/client"
 	ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
@@ -30,7 +29,7 @@ func handleContainer(w worker) gwclient.BuildFunc {
 				return nil, nil, fmt.Errorf("error creating rpm: %w", err)
 			}
 
-			img, err := resolveBaseConfig(ctx, w, client, platform, spec, targetKey)
+			img, err := resolveBaseConfig(ctx, w, sOpt, platform, spec, targetKey)
 			if err != nil {
 				return nil, nil, errors.Wrap(err, "could not resolve base image config")
 			}
@@ -50,9 +49,13 @@ func specToContainerLLB(w worker, spec *dalec.Spec, targetKey string, rpmDir llb
 		return llb.Scratch(), err
 	}
 
-	rootfs := llb.Scratch()
-	if ref := dalec.GetBaseOutputImage(spec, targetKey); ref != "" {
-		rootfs = llb.Image(ref, llb.WithMetaResolver(sOpt.Resolver), dalec.WithConstraints(opts...))
+	bi, err := spec.GetSingleBase(targetKey)
+	if err != nil {
+		return llb.Scratch(), err
+	}
+	rootfs, err := bi.ToState(sOpt, opts...)
+	if err != nil {
+		return llb.Scratch(), err
 	}
 
 	installTimeRepos := spec.GetInstallRepos(targetKey)
@@ -84,13 +87,18 @@ func specToContainerLLB(w worker, spec *dalec.Spec, targetKey string, rpmDir llb
 	return rootfs, nil
 }
 
-func resolveBaseConfig(ctx context.Context, w worker, resolver llb.ImageMetaResolver, platform *ocispecs.Platform, spec *dalec.Spec, targetKey string) (*dalec.DockerImageSpec, error) {
+func resolveBaseConfig(ctx context.Context, w worker, sOpt dalec.SourceOpts, platform *ocispecs.Platform, spec *dalec.Spec, targetKey string) (*dalec.DockerImageSpec, error) {
 	var img *dalec.DockerImageSpec
 
-	if ref := dalec.GetBaseOutputImage(spec, targetKey); ref != "" {
-		_, _, dt, err := resolver.ResolveImageConfig(ctx, ref, sourceresolver.Opt{Platform: platform})
+	bi, err := spec.GetSingleBase(targetKey)
+	if err != nil {
+		return nil, errors.Wrap(err, "error resolving base image config")
+	}
+
+	if bi != nil {
+		dt, err := bi.ResolveImageConfig(ctx, sOpt, platform)
 		if err != nil {
-			return nil, errors.Wrap(err, "error resolving base image config")
+			return nil, err
 		}
 
 		var i dalec.DockerImageSpec
@@ -100,7 +108,7 @@ func resolveBaseConfig(ctx context.Context, w worker, resolver llb.ImageMetaReso
 		img = &i
 	} else {
 		var err error
-		img, err = w.DefaultImageConfig(ctx, resolver, platform)
+		img, err = w.DefaultImageConfig(ctx, sOpt.Resolver, platform)
 		if err != nil {
 			return nil, errors.Wrap(err, "error resolving default image config")
 		}

frontend/azlinux/handle_depsonly.go

@@ -49,7 +49,7 @@ func handleDepsOnly(w worker) gwclient.BuildFunc {
 				return nil, nil, err
 			}
 
-			img, err := resolveBaseConfig(ctx, w, client, platform, spec, targetKey)
+			img, err := resolveBaseConfig(ctx, w, sOpt, platform, spec, targetKey)
 			if err != nil {
 				return nil, nil, err
 			}

frontend/azlinux/handle_rpm.go

@@ -56,7 +56,7 @@ func handleRPM(w worker) gwclient.BuildFunc {
 			if imgRef, err := runTests(ctx, client, w, spec, sOpt, st, targetKey, pg); err != nil {
 				// return the container ref in case of error so it can be used to debug
 				// the installed package state.
-				cfg, _ := resolveBaseConfig(ctx, w, client, platform, spec, targetKey)
+				cfg, _ := resolveBaseConfig(ctx, w, sOpt, platform, spec, targetKey)
 				return imgRef, cfg, err
 			}
 
@@ -94,7 +94,7 @@ func runTests(ctx context.Context, client gwclient.Client, w worker, spec *dalec
 	}
 
 	err = frontend.RunTests(ctx, client, spec, ref, withDeps, targetKey)
-	return ref, errors.Wrap(err, "TESTS FAILED")
+	return ref, err
 }
 
 var azlinuxRepoPlatform = dalec.RepoPlatformConfig{

frontend/deb/distro/container.go

@@ -12,13 +12,23 @@ import (
 )
 
 func (c *Config) BuildContainer(worker llb.State, sOpt dalec.SourceOpts, client gwclient.Client, spec *dalec.Spec, targetKey string, debSt llb.State, opts ...llb.ConstraintsOpt) (llb.State, error) {
-	base := dalec.GetBaseOutputImage(spec, targetKey)
-	if base == "" {
-		base = c.DefaultOutputImage
+	bi, err := spec.GetSingleBase(targetKey)
+	if err != nil {
+		return llb.Scratch(), err
 	}
 
-	if base == "" {
-		return llb.Scratch(), fmt.Errorf("no output image ref specified, cannot build from scratch")
+	var baseImg llb.State
+	if bi != nil {
+		img, err := bi.ToState(sOpt, opts...)
+		if err != nil {
+			return llb.Scratch(), err
+		}
+		baseImg = img
+	} else {
+		if c.DefaultOutputImage == "" {
+			return llb.Scratch(), fmt.Errorf("no output image ref specified, cannot build from scratch")
+		}
+		baseImg = llb.Image(c.DefaultOutputImage, llb.WithMetaResolver(sOpt.Resolver), dalec.WithConstraints(opts...))
 	}
 
 	opts = append(opts, dalec.ProgressGroup("Build Container Image"))
@@ -31,8 +41,6 @@ func (c *Config) BuildContainer(worker llb.State, sOpt dalec.SourceOpts, client
 		return llb.Scratch(), err
 	}
 
-	baseImg := llb.Image(base, llb.WithMetaResolver(sOpt.Resolver), dalec.WithConstraints(opts...))
-
 	debug := llb.Scratch().File(llb.Mkfile("debug", 0o644, []byte(`debug=2`)), opts...)
 	opts = append(opts, dalec.ProgressGroup("Install spec package"))
 
@@ -93,7 +101,7 @@ func (c *Config) HandleContainer(ctx context.Context, client gwclient.Client) (*
 			return nil, nil, err
 		}
 
-		img, err := c.BuildImageConfig(ctx, client, spec, platform, targetKey)
+		img, err := c.BuildImageConfig(ctx, sOpt, spec, platform, targetKey)
 		if err != nil {
 			return nil, nil, err
 		}

frontend/deb/distro/distro.go

@@ -7,7 +7,6 @@ import (
 	"github.com/Azure/dalec"
 	"github.com/Azure/dalec/frontend"
 	"github.com/moby/buildkit/client/llb"
-	"github.com/moby/buildkit/client/llb/sourceresolver"
 	gwclient "github.com/moby/buildkit/frontend/gateway/client"
 	"github.com/moby/buildkit/frontend/subrequests/targets"
 	ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
@@ -39,8 +38,8 @@ type Config struct {
 	ExtraRepos []dalec.PackageRepositoryConfig
 }
 
-func (cfg *Config) BuildImageConfig(ctx context.Context, resolver llb.ImageMetaResolver, spec *dalec.Spec, platform *ocispecs.Platform, targetKey string) (*dalec.DockerImageSpec, error) {
-	img, err := resolveConfig(ctx, resolver, spec, platform, targetKey)
+func (cfg *Config) BuildImageConfig(ctx context.Context, sOpt dalec.SourceOpts, spec *dalec.Spec, platform *ocispecs.Platform, targetKey string) (*dalec.DockerImageSpec, error) {
+	img, err := resolveConfig(ctx, sOpt, spec, platform, targetKey)
 	if err != nil {
 		return nil, err
 	}
@@ -52,17 +51,19 @@ func (cfg *Config) BuildImageConfig(ctx context.Context, resolver llb.ImageMetaR
 	return img, nil
 }
 
-func resolveConfig(ctx context.Context, resolver llb.ImageMetaResolver, spec *dalec.Spec, platform *ocispecs.Platform, targetKey string) (*dalec.DockerImageSpec, error) {
-	ref := dalec.GetBaseOutputImage(spec, targetKey)
-	if ref == "" {
+func resolveConfig(ctx context.Context, sOpt dalec.SourceOpts, spec *dalec.Spec, platform *ocispecs.Platform, targetKey string) (*dalec.DockerImageSpec, error) {
+	bi, err := spec.GetSingleBase(targetKey)
+	if err != nil {
+		return nil, err
+	}
+
+	if bi == nil {
 		return dalec.BaseImageConfig(platform), nil
 	}
 
-	_, _, dt, err := resolver.ResolveImageConfig(ctx, ref, sourceresolver.Opt{
-		Platform: platform,
-	})
+	dt, err := bi.ResolveImageConfig(ctx, sOpt, platform)
 	if err != nil {
-		return nil, err
+		return nil, errors.Wrap(err, "error resolving base image config")
 	}
 
 	var img dalec.DockerImageSpec

frontend/deb/distro/pkg.go

@@ -178,7 +178,7 @@ func (cfg *Config) HandleDeb(ctx context.Context, client gwclient.Client) (*gwcl
 		}
 
 		if ref, err := cfg.runTests(ctx, client, spec, sOpt, targetKey, ctr, pg); err != nil {
-			cfg, _ := cfg.BuildImageConfig(ctx, client, spec, platform, targetKey)
+			cfg, _ := cfg.BuildImageConfig(ctx, sOpt, spec, platform, targetKey)
 			return ref, cfg, err
 		}
 

frontend/windows/handle_container.go

@@ -10,7 +10,6 @@ import (
 	"github.com/Azure/dalec"
 	"github.com/Azure/dalec/frontend"
 	"github.com/moby/buildkit/client/llb"
-	"github.com/moby/buildkit/client/llb/sourceresolver"
 	"github.com/moby/buildkit/frontend/dockerui"
 	gwclient "github.com/moby/buildkit/frontend/gateway/client"
 	ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
@@ -84,14 +83,18 @@ func handleContainer(ctx context.Context, client gwclient.Client) (*gwclient.Res
 			return nil, nil, err
 		}
 
-		imgRef := dalec.GetBaseOutputImage(spec, targetKey)
-		if imgRef == "" {
-			imgRef = defaultBaseImage
+		bi, err := spec.GetSingleBase(targetKey)
+		if err != nil {
+			return nil, nil, err
 		}
 
-		_, _, dt, err := client.ResolveImageConfig(ctx, imgRef, sourceresolver.Opt{
-			Platform: &targetPlatform,
-		})
+		if bi == nil {
+			bi = &dalec.BaseImage{Rootfs: dalec.Source{
+				DockerImage: &dalec.SourceDockerImage{Ref: defaultBaseImage},
+			}}
+		}
+
+		dt, err := bi.ResolveImageConfig(ctx, sOpt, &targetPlatform)
 		if err != nil {
 			return nil, nil, errors.Wrap(err, "could not resolve base image config")
 		}