build: add cache-from and cache-to support

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

build/build.go

@@ -47,6 +47,9 @@ type Options struct {
 	Exports   []client.ExportEntry
 	Session   []session.Attachable
 
+	CacheFrom []client.CacheOptionsEntry
+	CacheTo   []client.CacheOptionsEntry
+
 	// DockerTarget
 }
 
@@ -133,10 +136,27 @@ func Build(ctx context.Context, drivers []DriverInfo, opt map[string]Options, do
 			}
 		}
 
+		if v, ok := opt.BuildArgs["BUILDKIT_INLINE_CACHE"]; ok {
+			if v, _ := strconv.ParseBool(v); v {
+				opt.CacheTo = append(opt.CacheTo, client.CacheOptionsEntry{
+					Type:  "inline",
+					Attrs: map[string]string{},
+				})
+			}
+		}
+
+		for _, e := range opt.CacheTo {
+			if e.Type != "inline" && !d.Features()[driver.CacheExport] {
+				return nil, notSupported(d, driver.CacheExport)
+			}
+		}
+
 		so := client.SolveOpt{
 			Frontend:      "dockerfile.v0",
 			FrontendAttrs: map[string]string{},
 			LocalDirs:     map[string]string{},
+			CacheExports:  opt.CacheTo,
+			CacheImports:  opt.CacheFrom,
 		}
 
 		switch len(opt.Exports) {

build/cache.go

@@ -0,0 +1,60 @@
+package build
+
+import (
+	"encoding/csv"
+	"strings"
+
+	"github.com/moby/buildkit/client"
+	"github.com/pkg/errors"
+)
+
+func ParseCacheEntry(in []string) ([]client.CacheOptionsEntry, error) {
+	imports := make([]client.CacheOptionsEntry, 0, len(in))
+	for _, in := range in {
+		csvReader := csv.NewReader(strings.NewReader(in))
+		fields, err := csvReader.Read()
+		if err != nil {
+			return nil, err
+		}
+		if isRefOnlyFormat(fields) {
+			for _, field := range fields {
+				imports = append(imports, client.CacheOptionsEntry{
+					Type:  "registry",
+					Attrs: map[string]string{"ref": field},
+				})
+			}
+			continue
+		}
+		im := client.CacheOptionsEntry{
+			Attrs: map[string]string{},
+		}
+		for _, field := range fields {
+			parts := strings.SplitN(field, "=", 2)
+			if len(parts) != 2 {
+				return nil, errors.Errorf("invalid value %s", field)
+			}
+			key := strings.ToLower(parts[0])
+			value := parts[1]
+			switch key {
+			case "type":
+				im.Type = value
+			default:
+				im.Attrs[key] = value
+			}
+		}
+		if im.Type == "" {
+			return nil, errors.Errorf("type required form> %q", in)
+		}
+		imports = append(imports, im)
+	}
+	return imports, nil
+}
+
+func isRefOnlyFormat(in []string) bool {
+	for _, v := range in {
+		if strings.Contains(v, "=") {
+			return false
+		}
+	}
+	return true
+}