Add --analyze flag to skaffold init

cmd/skaffold/app/cmd/init.go

@@ -18,6 +18,7 @@ package cmd
 
 import (
 	"bufio"
+	"encoding/json"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -52,6 +53,7 @@ var (
 	cliArtifacts []string
 	skipBuild    bool
 	force        bool
+	analyze      bool
 )
 
 // NewCmdInit describes the CLI command to generate a Skaffold configuration.
@@ -69,6 +71,7 @@ func NewCmdInit(out io.Writer) *cobra.Command {
 	cmd.Flags().BoolVar(&force, "force", false, "Force the generation of the Skaffold config")
 	cmd.Flags().StringVar(&composeFile, "compose-file", "", "Initialize from a docker-compose file")
 	cmd.Flags().StringArrayVarP(&cliArtifacts, "artifact", "a", nil, "'='-delimited dockerfile/image pair to generate build artifact\n(example: --artifact=/web/Dockerfile.web=gcr.io/web-project/image)")
+	cmd.Flags().BoolVar(&analyze, "analyze", false, "Print all discoverable Dockerfiles and images in JSON format to stdout")
 	return cmd
 }
 
@@ -125,6 +128,10 @@ func doInit(out io.Writer) error {
 		}
 	}
 
+	if analyze {
+		return printAnalyzeJSON(out, dockerfiles, images)
+	}
+
 	var pairs []dockerfilePair
 	// conditionally generate build artifacts
 	if !skipBuild {
@@ -189,6 +196,22 @@ func doInit(out io.Writer) error {
 	return nil
 }
 
+func printAnalyzeJSON(out io.Writer, dockerfiles, images []string) error {
+	a := struct {
+		Dockerfiles []string `json:"dockerfiles,omitempty"`
+		Images      []string `json:"images,omitempty"`
+	}{
+		Dockerfiles: dockerfiles,
+		Images:      images,
+	}
+	contents, err := json.Marshal(a)
+	if err != nil {
+		return errors.Wrap(err, "marshalling contents")
+	}
+	_, err = out.Write(contents)
+	return err
+}
+
 func processCliArtifacts(artifacts []string) ([]dockerfilePair, error) {
 	var pairs []dockerfilePair
 	for _, artifact := range artifacts {

cmd/skaffold/app/cmd/init_test.go

@@ -17,6 +17,7 @@ limitations under the License.
 package cmd
 
 import (
+	"bytes"
 	"fmt"
 	"testing"
 
@@ -60,3 +61,40 @@ deploy:
 
 	testutil.CheckErrorAndDeepEqual(t, false, err, expectedYaml, string(buf))
 }
+
+func TestPrintAnalyzeJSON(t *testing.T) {
+	tests := []struct {
+		name        string
+		dockerfiles []string
+		images      []string
+		expected    string
+	}{
+		{
+			name:        "dockerfile and image",
+			dockerfiles: []string{"Dockerfile", "Dockerfile_2"},
+			images:      []string{"image1", "image2"},
+			expected:    "{\"dockerfiles\":[\"Dockerfile\",\"Dockerfile_2\"],\"images\":[\"image1\",\"image2\"]}",
+		},
+		{
+			name:     "no dockerfile",
+			images:   []string{"image1", "image2"},
+			expected: "{\"images\":[\"image1\",\"image2\"]}",
+		},
+		{
+			name:        "no images",
+			dockerfiles: []string{"Dockerfile", "Dockerfile_2"},
+			expected:    "{\"dockerfiles\":[\"Dockerfile\",\"Dockerfile_2\"]}",
+		},
+		{
+			name:     "no dockerfiles or images",
+			expected: "{}",
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			out := bytes.NewBuffer([]byte{})
+			err := printAnalyzeJSON(out, test.dockerfiles, test.images)
+			testutil.CheckErrorAndDeepEqual(t, false, err, test.expected, out.String())
+		})
+	}
+}

docs/content/en/docs/references/cli/_index.md

@@ -335,6 +335,7 @@ Usage:
   skaffold init [flags]
 
 Flags:
+      --analyze                Print all discoverable Dockerfiles and images in JSON format to stdout
   -a, --artifact stringArray   '='-delimited dockerfile/image pair to generate build artifact
                                (example: --artifact=/web/Dockerfile.web=gcr.io/web-project/image)
       --compose-file string    Initialize from a docker-compose file
@@ -350,6 +351,7 @@ Global Flags:
 ```
 Env vars:
 
+* `SKAFFOLD_ANALYZE` (same as --analyze)
 * `SKAFFOLD_ARTIFACT` (same as --artifact)
 * `SKAFFOLD_COMPOSE_FILE` (same as --compose-file)
 * `SKAFFOLD_FILENAME` (same as --filename)