Allow environment variables to be used in docker build argument

docs/content/en/schemas/v1beta8.json

@@ -1191,11 +1191,11 @@
             "type": "string"
           },
           "type": "object",
-          "description": "arguments passed to the docker build.",
-          "x-intellij-html-description": "arguments passed to the docker build.",
+          "description": "arguments passed to the docker build. It also accepts environment variables via the go template syntax.",
+          "x-intellij-html-description": "arguments passed to the docker build. It also accepts environment variables via the go template syntax.",
           "default": "{}",
           "examples": [
-            "{\"key1\": \"value1\", \"key2\": \"value2\"}"
+            "{\"key1\": \"value1\", \"key2\": \"value2\", \"key3\": \"{{.ENV_VARIABLE}}\"}"
           ]
         },
         "buildContext": {

integration/examples/nodejs/backend/Dockerfile

@@ -1,8 +1,10 @@
 FROM node:8.12.0-alpine
 
+ARG SCRIPT
+ENV SCRIPT ${SCRIPT}
 WORKDIR /opt/backend
 EXPOSE 3000
-CMD ["npm", "run", "dev"]
+CMD ["npm", "run", ${SCRIPT}]
 
 COPY . .
 RUN npm install

integration/examples/nodejs/skaffold.yaml

@@ -4,6 +4,9 @@ build:
   artifacts:
   - image: gcr.io/k8s-skaffold/node-example
     context: backend
+    docker:
+      buildArgs:
+        SCRIPT: "{{.SCRIPT_ENV}}"
     sync:
       '*.js': .
 deploy:

integration/run_test.go

@@ -45,6 +45,7 @@ func TestRun(t *testing.T) {
 		}, {
 			description: "nodejs",
 			dir:         "examples/nodejs",
+			env:         []string{"SCRIPT_ENV=dev"},
 			pods:        []string{"node"},
 		}, {
 			description: "structure-tests",

pkg/skaffold/docker/image.go

@@ -339,7 +339,11 @@ func GetBuildArgs(a *latest.DockerArtifact) []string {
 		if v == nil {
 			args = append(args, k)
 		} else {
-			args = append(args, fmt.Sprintf("%s=%s", k, *v))
+			value, err := evaluateBuildArgsValue(*v)
+			if err != nil {
+				logrus.Errorf("unable to get value for build arg: %s", k)
+			}
+			args = append(args, fmt.Sprintf("%s=%s", k, value))
 		}
 	}
 

pkg/skaffold/docker/image_test.go

@@ -172,6 +172,7 @@ func TestGetBuildArgs(t *testing.T) {
 	tests := []struct {
 		description string
 		artifact    *latest.DockerArtifact
+		env         []string
 		want        []string
 	}{
 		{
@@ -180,9 +181,11 @@ func TestGetBuildArgs(t *testing.T) {
 				BuildArgs: map[string]*string{
 					"key1": util.StringPtr("value1"),
 					"key2": nil,
+					"key3": util.StringPtr("{{.FOO}}"),
 				},
 			},
-			want: []string{"--build-arg", "key1=value1", "--build-arg", "key2"},
+			env:  []string{"FOO=bar"},
+			want: []string{"--build-arg", "key1=value1", "--build-arg", "key2", "--build-arg", "key3=bar"},
 		},
 		{
 			description: "cache from",
@@ -212,6 +215,9 @@ func TestGetBuildArgs(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.description, func(t *testing.T) {
+			util.OSEnviron = func() []string {
+				return tt.env
+			}
 			result := GetBuildArgs(tt.artifact)
 			if diff := cmp.Diff(result, tt.want); diff != "" {
 				t.Errorf("%T differ (-got, +want): %s", tt.want, diff)

pkg/skaffold/docker/parse.go

@@ -44,7 +44,16 @@ type from struct {
 // RetrieveImage is overridden for unit testing
 var RetrieveImage = retrieveImage
 
-func expandBuildArgs(nodes []*parser.Node, buildArgs map[string]*string) {
+func evaluateBuildArgsValue(nameTemplate string) (string, error) {
+	tmpl, err := util.ParseEnvTemplate(nameTemplate)
+	if err != nil {
+		return "", errors.Wrap(err, "parsing template")
+	}
+
+	return util.ExecuteEnvTemplate(tmpl, nil)
+}
+
+func expandBuildArgs(nodes []*parser.Node, buildArgs map[string]*string) error {
 	for i, node := range nodes {
 		if node.Value != command.Arg {
 			continue
@@ -56,8 +65,12 @@ func expandBuildArgs(nodes []*parser.Node, buildArgs map[string]*string) {
 
 		// build arg's value
 		var value string
+		var err error
 		if buildArgs[key] != nil {
-			value = *buildArgs[key]
+			value, err = evaluateBuildArgsValue(*buildArgs[key])
+			if err != nil {
+				return errors.Wrapf(err, "unable to get value for build arg: %s", key)
+			}
 		} else if len(keyValue) > 1 {
 			value = keyValue[1]
 		}
@@ -74,6 +87,7 @@ func expandBuildArgs(nodes []*parser.Node, buildArgs map[string]*string) {
 			}
 		}
 	}
+	return nil
 }
 
 func fromInstructions(nodes []*parser.Node) []from {
@@ -181,7 +195,10 @@ func readDockerfile(workspace, absDockerfilePath string, buildArgs map[string]*s
 
 	dockerfileLines := res.AST.Children
 
-	expandBuildArgs(dockerfileLines, buildArgs)
+	err = expandBuildArgs(dockerfileLines, buildArgs)
+	if err != nil {
+		return nil, errors.Wrap(err, "putting build arguments")
+	}
 
 	instructions, err := onbuildInstructions(dockerfileLines)
 	if err != nil {

pkg/skaffold/docker/parse_test.go

@@ -225,6 +225,7 @@ func TestGetDependencies(t *testing.T) {
 		workspace   string
 		ignore      string
 		buildArgs   map[string]*string
+		env         []string
 
 		expected  []string
 		fetched   []string
@@ -486,10 +487,22 @@ func TestGetDependencies(t *testing.T) {
 			expected:    []string{"Dockerfile", "file"},
 			fetched:     []string{"jboss/wildfly:14.0.1.Final"},
 		},
+		{
+			description: "build args with an environment variable",
+			dockerfile:  copyServerGoBuildArg,
+			workspace:   ".",
+			buildArgs:   map[string]*string{"FOO": util.StringPtr("{{.FILE_NAME}}")},
+			env:         []string{"FILE_NAME=server.go"},
+			expected:    []string{"Dockerfile", "server.go"},
+			fetched:     []string{"ubuntu:14.04"},
+		},
 	}
 
 	for _, test := range tests {
 		t.Run(test.description, func(t *testing.T) {
+			util.OSEnviron = func() []string {
+				return test.env
+			}
 			tmpDir, cleanup := testutil.NewTempDir(t)
 			defer cleanup()
 

pkg/skaffold/schema/latest/config.go

@@ -591,7 +591,8 @@ type KanikoArtifact struct {
 	Target string `yaml:"target,omitempty"`
 
 	// BuildArgs are arguments passed to the docker build.
-	// For example: `{"key1": "value1", "key2": "value2"}`.
+	// It also accepts environment variables via the go template syntax.
+	// For example: `{"key1": "value1", "key2": "value2", "key3": "{{.ENV_VARIABLE}}"}`.
 	BuildArgs map[string]*string `yaml:"buildArgs,omitempty"`
 
 	// BuildContext is where the build context for this artifact resides.