fix(build): wire devcontainer.json cacheFrom into docker build args

pkg/devcontainer/build/options.go

@@ -154,7 +154,11 @@ func NewOptions(params NewOptionsParams) (*BuildOptions, error) {
 				),
 			}
 		}
-	} else {
+	}
+	if configCacheFrom := params.ParsedConfig.Config.GetCacheFrom(); len(configCacheFrom) > 0 {
+		buildOptions.CacheFrom = append(buildOptions.CacheFrom, configCacheFrom...)
+	}
+	if len(buildOptions.CacheFrom) == 0 {
 		buildOptions.BuildArgs["BUILDKIT_INLINE_CACHE"] = "1"
 	}
 

pkg/devcontainer/build/options_test.go

@@ -0,0 +1,86 @@
+package build
+
+import (
+	"testing"
+
+	"github.com/devsy-org/devsy/pkg/devcontainer/config"
+	"github.com/devsy-org/devsy/pkg/provider"
+	"github.com/devsy-org/devsy/pkg/types"
+)
+
+const testCacheImage = "myregistry.io/cache:latest"
+
+func substitutedConfig(cfg *config.DevContainerConfig) *config.SubstitutedConfig {
+	return &config.SubstitutedConfig{Config: cfg, Raw: cfg}
+}
+
+func TestNewOptions_CacheFrom_ConfigOnly(t *testing.T) {
+	params := NewOptionsParams{
+		ParsedConfig: substitutedConfig(&config.DevContainerConfig{
+			DockerfileContainer: config.DockerfileContainer{
+				Build: &config.ConfigBuildOptions{
+					CacheFrom: types.StrArray{testCacheImage, "other:tag"},
+				},
+			},
+		}),
+		Options: provider.BuildOptions{},
+	}
+	opts, err := NewOptions(params)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(opts.CacheFrom) != 2 {
+		t.Fatalf("expected 2 CacheFrom entries, got %d: %v", len(opts.CacheFrom), opts.CacheFrom)
+	}
+	if opts.CacheFrom[0] != testCacheImage || opts.CacheFrom[1] != "other:tag" {
+		t.Fatalf("unexpected CacheFrom: %v", opts.CacheFrom)
+	}
+	if _, ok := opts.BuildArgs["BUILDKIT_INLINE_CACHE"]; ok {
+		t.Fatal("BUILDKIT_INLINE_CACHE should not be set when cacheFrom is configured")
+	}
+}
+
+func TestNewOptions_CacheFrom_CLIAndConfig(t *testing.T) {
+	params := NewOptionsParams{
+		ParsedConfig: substitutedConfig(&config.DevContainerConfig{
+			DockerfileContainer: config.DockerfileContainer{
+				Build: &config.ConfigBuildOptions{
+					CacheFrom: types.StrArray{testCacheImage},
+				},
+			},
+		}),
+		Options: provider.BuildOptions{
+			RegistryCache: "registry.example.com/cache",
+		},
+	}
+	opts, err := NewOptions(params)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(opts.CacheFrom) != 2 {
+		t.Fatalf("expected 2 CacheFrom entries, got %d: %v", len(opts.CacheFrom), opts.CacheFrom)
+	}
+	if opts.CacheFrom[0] != "type=registry,ref=registry.example.com/cache" {
+		t.Fatalf("expected CLI registry cache first, got: %s", opts.CacheFrom[0])
+	}
+	if opts.CacheFrom[1] != testCacheImage {
+		t.Fatalf("expected config cache second, got: %s", opts.CacheFrom[1])
+	}
+}
+
+func TestNewOptions_CacheFrom_Fallback(t *testing.T) {
+	params := NewOptionsParams{
+		ParsedConfig: substitutedConfig(&config.DevContainerConfig{}),
+		Options:      provider.BuildOptions{},
+	}
+	opts, err := NewOptions(params)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(opts.CacheFrom) != 0 {
+		t.Fatalf("expected empty CacheFrom, got: %v", opts.CacheFrom)
+	}
+	if opts.BuildArgs["BUILDKIT_INLINE_CACHE"] != "1" {
+		t.Fatal("expected BUILDKIT_INLINE_CACHE=1 as fallback")
+	}
+}