Include tags when --push=false is set

- Refactor noop into its own publisher.
- Use :tag@sha format in digest when --push=false is set.
- Allow --tag-only to be used with --push=false. This includes
  validations that prevent --tag-only to be used with no tags or the
  `latest` tag.

Signed-off-by: Adam Kaplan <adam@adambkaplan.com>

.github/workflows/e2e.yaml

@@ -57,6 +57,10 @@ jobs:
           docker run ${testimg} --wait=false -f HEAD
         fi
 
+        # Check that building without push prints the tag (and sha)
+        go run ./ build --push=false -t test ./test | grep ":test@sha256:"
+        go run ./ build --push=false -t test --tag-only ./test | grep ":test$"
+
         # Check that using ldflags to set variables works.
         cat > .ko.yaml << EOF
         builds:

pkg/commands/resolver.go

@@ -224,10 +224,15 @@ func makePublisher(po *options.PublishOptions) (publish.Interface, error) {
 		// If not publishing, at least generate a digest to simulate
 		// publishing.
 		if len(publishers) == 0 {
-			publishers = append(publishers, nopPublisher{
-				repoName: repoName,
-				namer:    namer,
-			})
+			noop, err := publish.NewNoOp(repoName,
+				publish.NoOpWithNamer(namer),
+				publish.NoOpWithTags(po.Tags),
+				publish.NoOpWithTagOnly(po.TagOnly),
+			)
+			if err != nil {
+				return nil, err
+			}
+			publishers = append(publishers, noop)
 		}
 
 		return publish.MultiPublisher(publishers...), nil
@@ -251,24 +256,6 @@ func makePublisher(po *options.PublishOptions) (publish.Interface, error) {
 	return publish.NewCaching(innerPublisher)
 }
 
-// nopPublisher simulates publishing without actually publishing anything, to
-// provide fallback behavior when the user configures no push destinations.
-type nopPublisher struct {
-	repoName string
-	namer    publish.Namer
-}
-
-func (n nopPublisher) Publish(_ context.Context, br build.Result, s string) (name.Reference, error) {
-	s = strings.TrimPrefix(s, build.StrictScheme)
-	h, err := br.Digest()
-	if err != nil {
-		return nil, err
-	}
-	return name.NewDigest(fmt.Sprintf("%s@%s", n.namer(n.repoName, s), h))
-}
-
-func (n nopPublisher) Close() error { return nil }
-
 // resolvedFuture represents a "future" for the bytes of a resolved file.
 type resolvedFuture chan []byte
 

pkg/publish/noop.go

@@ -0,0 +1,99 @@
+// Copyright 2022 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package publish
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/google/go-containerregistry/pkg/name"
+	"github.com/google/ko/pkg/build"
+)
+
+// Original spelling was preserved when this was refactored out of pkg/commands
+type nopPublisher struct {
+	repoName string
+	namer    Namer
+	tag      string
+	tagOnly  bool
+}
+
+type noOpOpener struct {
+	repoName string
+	namer    Namer
+	tags     []string
+	tagOnly  bool
+}
+
+// NoOpOption provides functional options to the NoOp publisher.
+type NoOpOption func(*noOpOpener)
+
+func (o *noOpOpener) Open() (Interface, error) {
+	tag := defaultTags[0]
+	if o.tagOnly {
+		// Replicate the tag-only validations in the default publisher
+		if len(o.tags) != 1 {
+			return nil, errors.New("must specify exactly one tag to resolve images into tag-only references")
+		}
+		if o.tags[0] == defaultTags[0] {
+			return nil, errors.New("latest tag cannot be used in tag-only references")
+		}
+	}
+	// If one or more tags are specified, use the first tag in the list
+	if len(o.tags) >= 1 {
+		tag = o.tags[0]
+	}
+	return &nopPublisher{
+		repoName: o.repoName,
+		namer:    o.namer,
+		tag:      tag,
+		tagOnly:  o.tagOnly,
+	}, nil
+}
+
+// NewNoOp returns a publisher.Interface that simulates publishing without actually publishing
+// anything, to provide fallback behavior when the user configures no push destinations.
+func NewNoOp(baseName string, options ...NoOpOption) (Interface, error) {
+	nop := &noOpOpener{
+		repoName: baseName,
+		namer:    identity,
+	}
+	for _, option := range options {
+		option(nop)
+	}
+	return nop.Open()
+}
+
+// Publish implements publish.Interface
+func (n *nopPublisher) Publish(_ context.Context, br build.Result, s string) (name.Reference, error) {
+	s = strings.TrimPrefix(s, build.StrictScheme)
+	h, err := br.Digest()
+	if err != nil {
+		return nil, err
+	}
+	// If the tag is not empty or is not "latest", use the :tag@sha suffix
+	if n.tag != "" || n.tag != defaultTags[0] {
+		// If tag only, just return the tag
+		if n.tagOnly {
+			return name.NewTag(fmt.Sprintf("%s:%s", n.namer(n.repoName, s), n.tag))
+		}
+		return name.NewDigest(fmt.Sprintf("%s:%s@%s", n.namer(n.repoName, s), n.tag, h))
+	}
+	return name.NewDigest(fmt.Sprintf("%s@%s", n.namer(n.repoName, s), h))
+}
+
+func (n *nopPublisher) Close() error { return nil }

pkg/publish/noop_test.go

@@ -0,0 +1,187 @@
+// Copyright 2022 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package publish_test
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/google/go-containerregistry/pkg/v1/random"
+	"github.com/google/ko/pkg/build"
+	"github.com/google/ko/pkg/publish"
+)
+
+func TestNoOp(t *testing.T) {
+	repoName := "quarkus.io/charm"
+	importPath := "crane"
+	noop, err := publish.NewNoOp(repoName)
+	if err != nil {
+		t.Fatalf("NewNoOp() = %v", err)
+	}
+	img, err := random.Image(1024, 1)
+	if err != nil {
+		t.Fatalf("random.Image() = %v", err)
+	}
+	ref, err := noop.Publish(context.TODO(), img, build.StrictScheme+importPath)
+	if err != nil {
+		t.Fatalf("Publish() = %v", err)
+	}
+	if !strings.HasPrefix(ref.String(), repoName) {
+		t.Errorf("Publish() = %v, wanted preifx %s", ref, repoName)
+	}
+}
+
+func TestNoOpWithCustomNamer(t *testing.T) {
+	repoName := "quarkus.io/charm"
+	importPath := "crane"
+	noop, err := publish.NewNoOp(repoName, publish.NoOpWithNamer(md5Hash))
+	if err != nil {
+		t.Fatalf("NewNoOp() = %v", err)
+	}
+	img, err := random.Image(1024, 1)
+	if err != nil {
+		t.Fatalf("random.Image() = %v", err)
+	}
+	ref, err := noop.Publish(context.TODO(), img, build.StrictScheme+importPath)
+	if err != nil {
+		t.Fatalf("Publish() = %v", err)
+	}
+	if !strings.HasPrefix(ref.String(), repoName) {
+		t.Errorf("Publish() = %v, wanted preifx %s", ref, repoName)
+	}
+	if !strings.HasSuffix(ref.Context().String(), md5Hash("", strings.ToLower(importPath))) {
+		t.Errorf("Publish() = %v, wanted suffix %v", ref.Context(), md5Hash("", importPath))
+	}
+}
+
+func TestNoOpWithTags(t *testing.T) {
+	cases := []struct {
+		name            string
+		tags            []string
+		expectedTag     string
+		expectOpenError bool
+	}{
+		{
+			name: "no tags",
+		},
+		{
+			name: "latest tag",
+			tags: []string{"latest"},
+		},
+		{
+			name:        "multiple tags",
+			tags:        []string{"v0.1", "v0.1.1"},
+			expectedTag: "v0.1",
+		},
+		{
+			name:        "single tag",
+			tags:        []string{"v0.1"},
+			expectedTag: "v0.1",
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			repoName := "quarkus.io/charm"
+			importPath := "crane"
+			noop, err := publish.NewNoOp(repoName, publish.NoOpWithTags(tc.tags))
+			if tc.expectOpenError {
+				if err == nil {
+					t.Error("NewNoOp() - expected error, got none")
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("NewNoOp() = %v", err)
+			}
+			img, err := random.Image(1024, 1)
+			if err != nil {
+				t.Fatalf("random.Image() = %v", err)
+			}
+			ref, err := noop.Publish(context.TODO(), img, build.StrictScheme+importPath)
+			if err != nil {
+				t.Fatalf("Publish() = %v", err)
+			}
+			if !strings.HasPrefix(ref.String(), repoName) {
+				t.Errorf("Publish() = %v, wanted preifx %s", ref, repoName)
+			}
+			if tc.expectedTag != "" && !strings.Contains(ref.String(), fmt.Sprintf(":%s@", tc.expectedTag)) {
+				t.Errorf("Publish() = %v, expected tag %s", ref.String(), tc.expectedTag)
+			}
+		})
+	}
+}
+
+func TestNoOpWithTagOnly(t *testing.T) {
+	cases := []struct {
+		name            string
+		tags            []string
+		expectedTag     string
+		expectOpenError bool
+	}{
+		{
+			name:            "no tags",
+			expectOpenError: true,
+		},
+		{
+			name:            "latest tag",
+			tags:            []string{"latest"},
+			expectOpenError: true,
+		},
+		{
+			name:            "multiple tags",
+			tags:            []string{"v0.1", "v0.1.1"},
+			expectOpenError: true,
+		},
+		{
+			name:        "single tag",
+			tags:        []string{"v0.1"},
+			expectedTag: "v0.1",
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			repoName := "quarkus.io/charm"
+			importPath := "crane"
+			noop, err := publish.NewNoOp(repoName,
+				publish.NoOpWithTags(tc.tags),
+				publish.NoOpWithTagOnly(true))
+			if tc.expectOpenError {
+				if err == nil {
+					t.Error("NewNoOp() - expected error, got none")
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("NewNoOp() = %v", err)
+			}
+			img, err := random.Image(1024, 1)
+			if err != nil {
+				t.Fatalf("random.Image() = %v", err)
+			}
+			ref, err := noop.Publish(context.TODO(), img, build.StrictScheme+importPath)
+			if err != nil {
+				t.Fatalf("Publish() = %v", err)
+			}
+			if !strings.HasPrefix(ref.String(), repoName) {
+				t.Errorf("Publish() = %v, wanted preifx %s", ref, repoName)
+			}
+			if tc.expectedTag != "" && !strings.HasSuffix(ref.String(), fmt.Sprintf(":%s", tc.expectedTag)) {
+				t.Errorf("Publish() = %v, expected only tag %s", ref.String(), tc.expectedTag)
+			}
+		})
+	}
+}

pkg/publish/options.go

@@ -120,3 +120,21 @@ func Insecure(b bool) Option {
 		return nil
 	}
 }
+
+func NoOpWithNamer(n Namer) NoOpOption {
+	return func(noo *noOpOpener) {
+		noo.namer = n
+	}
+}
+
+func NoOpWithTags(t []string) NoOpOption {
+	return func(noo *noOpOpener) {
+		noo.tags = t
+	}
+}
+
+func NoOpWithTagOnly(to bool) NoOpOption {
+	return func(noo *noOpOpener) {
+		noo.tagOnly = to
+	}
+}