Write data about pushed images if env var is set

pkg/executor/push.go

@@ -18,10 +18,12 @@ package executor
 
 import (
 	"crypto/tls"
+	"encoding/json"
 	"fmt"
 	"io/ioutil"
 	"net/http"
 	"os"
+	"path/filepath"
 	"strings"
 	"time"
 
@@ -32,14 +34,15 @@ import (
 	"github.com/GoogleContainerTools/kaniko/pkg/timing"
 	"github.com/GoogleContainerTools/kaniko/pkg/version"
 	"github.com/google/go-containerregistry/pkg/name"
-	"github.com/google/go-containerregistry/pkg/v1"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/google/go-containerregistry/pkg/v1/empty"
 	"github.com/google/go-containerregistry/pkg/v1/layout"
 	"github.com/google/go-containerregistry/pkg/v1/mutate"
 	"github.com/google/go-containerregistry/pkg/v1/remote"
 	"github.com/google/go-containerregistry/pkg/v1/tarball"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
+	"github.com/spf13/afero"
 )
 
 type withUserAgent struct {
@@ -165,6 +168,39 @@ func DoPush(image v1.Image, opts *config.KanikoOptions) error {
 		}
 	}
 	timing.DefaultRun.Stop(t)
+	return writeImageOutputs(image, destRefs)
+}
+
+var fs = afero.NewOsFs()
+
+func writeImageOutputs(image v1.Image, destRefs []name.Tag) error {
+	dir := os.Getenv("BUILDER_OUTPUT")
+	if dir == "" {
+		return nil
+	}
+	f, err := fs.Create(filepath.Join(dir, "images"))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	d, err := image.Digest()
+	if err != nil {
+		return err
+	}
+
+	type imageOutput struct {
+		Name   string `json:"name"`
+		Digest string `json:"digest"`
+	}
+	for _, r := range destRefs {
+		if err := json.NewEncoder(f).Encode(imageOutput{
+			Name:   r.String(),
+			Digest: d.String(),
+		}); err != nil {
+			return err
+		}
+	}
 	return nil
 }
 

pkg/executor/push_test.go

@@ -18,18 +18,91 @@ package executor
 
 import (
 	"bytes"
+	"fmt"
 	"io/ioutil"
 	"net/http"
 	"os"
+	"path/filepath"
 	"testing"
 
 	"github.com/GoogleContainerTools/kaniko/pkg/config"
 	"github.com/GoogleContainerTools/kaniko/testutil"
+	"github.com/google/go-containerregistry/pkg/name"
 	"github.com/google/go-containerregistry/pkg/v1/layout"
 	"github.com/google/go-containerregistry/pkg/v1/random"
 	"github.com/google/go-containerregistry/pkg/v1/validate"
+	"github.com/spf13/afero"
 )
 
+func mustTag(t *testing.T, s string) name.Tag {
+	tag, err := name.NewTag(s, name.StrictValidation)
+	if err != nil {
+		t.Fatalf("NewTag: %v", err)
+	}
+	return tag
+}
+
+func TestWriteImageOutputs(t *testing.T) {
+	img, err := random.Image(1024, 3)
+	if err != nil {
+		t.Fatalf("random.Image: %v", err)
+	}
+	d, err := img.Digest()
+	if err != nil {
+		t.Fatalf("Digest: %v", err)
+	}
+
+	for _, c := range []struct {
+		desc, env string
+		tags      []name.Tag
+		want      string
+	}{{
+		desc: "env unset, no output",
+		env:  "",
+	}, {
+		desc: "env set, one tag",
+		env:  "/foo",
+		tags: []name.Tag{mustTag(t, "gcr.io/foo/bar:latest")},
+		want: fmt.Sprintf(`{"name":"gcr.io/foo/bar:latest","digest":%q}
+`, d),
+	}, {
+		desc: "env set, two tags",
+		env:  "/foo",
+		tags: []name.Tag{
+			mustTag(t, "gcr.io/foo/bar:latest"),
+			mustTag(t, "gcr.io/baz/qux:latest"),
+		},
+		want: fmt.Sprintf(`{"name":"gcr.io/foo/bar:latest","digest":%q}
+{"name":"gcr.io/baz/qux:latest","digest":%q}
+`, d, d),
+	}} {
+		t.Run(c.desc, func(t *testing.T) {
+			fs = afero.NewMemMapFs()
+			if c.want == "" {
+				fs = afero.NewReadOnlyFs(fs) // No files should be written.
+			}
+
+			os.Setenv("BUILDER_OUTPUT", c.env)
+			if err := writeImageOutputs(img, c.tags); err != nil {
+				t.Fatalf("writeImageOutputs: %v", err)
+			}
+
+			if c.want == "" {
+				return
+			}
+
+			b, err := afero.ReadFile(fs, filepath.Join(c.env, "images"))
+			if err != nil {
+				t.Fatalf("ReadFile: %v", err)
+			}
+
+			if got := string(b); got != c.want {
+				t.Fatalf(" got: %s\nwant: %s", got, c.want)
+			}
+		})
+	}
+}
+
 func TestHeaderAdded(t *testing.T) {
 	tests := []struct {
 		name     string