Inherit Docker/OCI LABELs during build

When building / pulling from a Docker/OCI source, retrieve LABELs from
the config, and ensure they are set in the resulting Singularity
container.

This fixes a longstanding regression from Singularity 2.x. Note that
you will now need to use `--force` in a build to override a label that
already exists in the source Docker/OCI container.

Fixes sylabs/singularity#146

CHANGELOG.md

@@ -8,6 +8,13 @@
     the `%test` section of the build with a ephemeral tmpfs overlay,
     permitting tests that write to the container filesystem.
 
+### Changed defaults / behaviours
+
+  - LABELs from Docker/OCI images are now inherited. This fixes a longstanding
+    regression from Singularity 2.x. Note that you will now need to use
+    `--force` in a build to override a label that already exists in the source
+    Docker/OCI container.
+
 ## v3.8.2 - [2021-08-31]
 
 ### Bug fixes

e2e/docker/docker.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/hpcng/singularity/e2e/internal/e2e"
@@ -410,6 +411,45 @@ func (c ctx) testDockerCMDQuotes(t *testing.T) {
 	)
 }
 
+func (c ctx) testDockerLabels(t *testing.T) {
+	imageDir, cleanup := e2e.MakeTempDir(t, c.env.TestDir, "labels-", "")
+	defer cleanup(t)
+	imagePath := filepath.Join(imageDir, "container")
+
+	// Test container & set labels
+	// See: https://github.com/sylabs/singularity-test-containers/pull/1
+	imgSrc := "docker://sylabsio/labels"
+	label1 := "LABEL1: 1"
+	label2 := "LABEL2: TWO"
+
+	c.env.RunSingularity(
+		t,
+		e2e.AsSubtest("build"),
+		e2e.WithProfile(e2e.RootProfile),
+		e2e.WithCommand("build"),
+		e2e.WithArgs(imagePath, imgSrc),
+		e2e.ExpectExit(0),
+	)
+
+	verifyOutput := func(t *testing.T, r *e2e.SingularityCmdResult) {
+		output := string(r.Stdout)
+		for _, l := range []string{label1, label2} {
+			if !strings.Contains(output, l) {
+				t.Errorf("Did not find expected label %s in inspect output", l)
+			}
+		}
+	}
+
+	c.env.RunSingularity(
+		t,
+		e2e.AsSubtest("inspect"),
+		e2e.WithProfile(e2e.UserProfile),
+		e2e.WithCommand("inspect"),
+		e2e.WithArgs([]string{"--labels", imagePath}...),
+		e2e.ExpectExit(0, verifyOutput),
+	)
+}
+
 // E2ETests is the main func to trigger the test suite
 func E2ETests(env e2e.TestEnv) testhelper.Tests {
 	c := ctx{
@@ -424,5 +464,6 @@ func E2ETests(env e2e.TestEnv) testhelper.Tests {
 		"registry":         c.testDockerRegistry,
 		"whiteout symlink": c.testDockerWhiteoutSymlink,
 		"cmd quotes":       c.testDockerCMDQuotes,
+		"labels":           c.testDockerLabels,
 	}
 }

internal/pkg/build/sources/conveyorPacker_oci.go

@@ -185,6 +185,11 @@ func (cp *OCIConveyorPacker) Pack(ctx context.Context) (*sytypes.Bundle, error)
 		return nil, fmt.Errorf("while inserting oci config: %v", err)
 	}
 
+	err = cp.insertOCILabels()
+	if err != nil {
+		return nil, fmt.Errorf("while inserting oci labels: %v", err)
+	}
+
 	return cp.b, nil
 }
 
@@ -208,7 +213,6 @@ func (cp *OCIConveyorPacker) getConfig(ctx context.Context) (imgspecv1.ImageConf
 	if err != nil {
 		return imgspecv1.ImageConfig{}, err
 	}
-
 	return imgSpec.Config, nil
 }
 
@@ -444,6 +448,20 @@ func (cp *OCIConveyorPacker) insertEnv() (err error) {
 	return nil
 }
 
+func (cp *OCIConveyorPacker) insertOCILabels() (err error) {
+	labels := cp.imgConfig.Labels
+	var text []byte
+
+	// make new map into json
+	text, err = json.MarshalIndent(labels, "", "\t")
+	if err != nil {
+		return err
+	}
+
+	err = ioutil.WriteFile(filepath.Join(cp.b.RootfsPath, "/.singularity.d/labels.json"), []byte(text), 0644)
+	return err
+}
+
 // CleanUp removes any tmpfs owned by the conveyorPacker on the filesystem
 func (cp *OCIConveyorPacker) CleanUp() {
 	cp.b.Remove()