Make OCI provider default to current arch

This was previously fixed by PR 152, but that PR introduced another bug.
Re-implement platform defaulting after the revert of PR 152.

Signed-off-by: Will Murphy <[email protected]>

client.go

@@ -3,6 +3,7 @@ package stereoscope
 import (
 	"context"
 	"fmt"
+	"runtime"
 
 	"github.com/wagoodman/go-partybus"
 
@@ -139,6 +140,7 @@ func selectImageProvider(imgStr string, source image.Source, cfg config) (image.
 		}
 		provider = oci.NewProviderFromTarball(imgStr, tempDirGenerator)
 	case image.OciRegistrySource:
+		defaultPlatformIfNil(&cfg)
 		provider = oci.NewProviderFromRegistry(imgStr, tempDirGenerator, cfg.Registry, cfg.Platform)
 	case image.SingularitySource:
 		if cfg.Platform != nil {
@@ -151,6 +153,15 @@ func selectImageProvider(imgStr string, source image.Source, cfg config) (image.
 	return provider, nil
 }
 
+func defaultPlatformIfNil(cfg *config) {
+	if cfg.Platform == nil {
+		p, err := image.NewPlatform(fmt.Sprintf("linux/%s", runtime.GOARCH))
+		if err == nil {
+			cfg.Platform = p
+		}
+	}
+}
+
 // GetImage parses the user provided image string and provides an image object;
 // note: the source where the image should be referenced from is automatically inferred.
 func GetImage(ctx context.Context, userStr string, options ...Option) (*image.Image, error) {

test/integration/platform_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"runtime"
 	"strings"
 	"testing"
 
@@ -133,6 +134,12 @@ func TestDigestThatNarrowsToOnePlatform(t *testing.T) {
 	}
 }
 
+func TestDefaultPlatformWithOciRegistry(t *testing.T) {
+	img, err := stereoscope.GetImageFromSource(context.TODO(), "busybox:1.31", image.OciRegistrySource)
+	require.NoError(t, err)
+	assertArchAndOs(t, img, runtime.GOARCH, "linux")
+}
+
 func assertArchAndOs(t *testing.T, img *image.Image, architecture string, os string) {
 	type platform struct {
 		Architecture string `json:"architecture"`