Added --ignore-unset CLI flag

engine/shell.go

@@ -8,11 +8,27 @@ import (
 )
 
 type ShellTemplate struct {
-	content []byte
+	content     []byte
+	ignoreUnset bool
 }
 
-func NewShellTemplate(template []byte) (Template, error) {
-	return ShellTemplate{template}, nil
+type ShellTemplateOption = func(*ShellTemplate) error
+
+func ShellTemplateIgnoreUnset() ShellTemplateOption {
+	return func(t *ShellTemplate) error {
+		t.ignoreUnset = true
+		return nil
+	}
+}
+
+func NewShellTemplate(template []byte, options ...ShellTemplateOption) (Template, error) {
+	tpl := ShellTemplate{template, false}
+	for _, option := range options {
+		if err := option(&tpl); err != nil {
+			return nil, err
+		}
+	}
+	return tpl, nil
 }
 
 func (t ShellTemplate) Render(data map[string]interface{}) (res []byte, err error) {
@@ -31,14 +47,14 @@ func (t ShellTemplate) Render(data map[string]interface{}) (res []byte, err erro
 			return nil, err
 		}
 	}
-	r, err := envsubst(string(t.content), data)
+	r, err := envsubst(string(t.content), data, t.ignoreUnset)
 	if err != nil {
 		return nil, err
 	}
 	return []byte(r), nil
 }
 
-func envsubst(value string, env map[string]interface{}) (res string, err error) {
+func envsubst(value string, env map[string]interface{}, ignoreUnset bool) (res string, err error) {
 	defer func() {
 		if r := recover(); r != nil {
 			if _, ok := r.(runtime.Error); ok {
@@ -47,23 +63,26 @@ func envsubst(value string, env map[string]interface{}) (res string, err error)
 			err = r.(error)
 		}
 	}()
-	res = expandWithLineColumnInfo(value, func(key string, line int, col int) string {
+	res = expandWithLineColumnInfo(value, func(key string, line int, col int) (string, bool) {
 		if key == "$" || key == "" {
-			return "$"
+			return "$", true
 		}
 		value, ok := env[key]
 		if !ok || value == nil {
+			if ignoreUnset {
+				return "", false
+			}
 			panic(fmt.Errorf("%d:%d: \"%s\" isn't set", line, col, key))
 		}
 		if !yamlext.IsBasicType(value) {
 			panic(fmt.Errorf("%d:%d: \"%s\" must be either a string, number or a boolean", line, col, key))
 		}
-		return fmt.Sprintf("%v", value)
+		return fmt.Sprintf("%v", value), true
 	})
 	return
 }
 
-func expandWithLineColumnInfo(s string, mapping func(string, int, int) string) string {
+func expandWithLineColumnInfo(s string, mapping func(string, int, int) (string, bool)) string {
 	buf := make([]byte, 0, 2*len(s))
 	i, l, n := 0, 0, 0
 	for j := 0; j < len(s); j++ {
@@ -73,7 +92,11 @@ func expandWithLineColumnInfo(s string, mapping func(string, int, int) string) s
 		} else if s[j] == '$' && j+1 < len(s) {
 			buf = append(buf, s[i:j]...)
 			name, w := getShellName(s[j+1:])
-			buf = append(buf, mapping(name, l+1, j-n+1)...)
+			if v, ok := mapping(name, l+1, j-n+1); ok {
+				buf = append(buf, v...)
+			} else {
+				buf = append(buf, s[j:j+1+w]...)
+			}
 			j += w
 			i = j + 1
 		}

engine/shell_test.go

@@ -11,7 +11,7 @@ func init() {
 
 func TestShellTemplateRender(t *testing.T) {
 	actual, err := ShellTemplate{
-		[]byte(`# kubetpl:syntax:$
+		content: []byte(`# kubetpl:syntax:$
 apiVersion: apps/v1beta1
 kind: Deployment
 metadata:
@@ -22,6 +22,7 @@ metadata:
 spec:
   replicas: $REPLICAS
 `),
+		ignoreUnset: false,
 	}.Render(map[string]interface{}{
 		"NAME":     "app",
 		"NOT_USED": "value",
@@ -48,11 +49,12 @@ spec:
 
 func TestShellTemplateRenderIncomplete(t *testing.T) {
 	_, err := ShellTemplate{
-		[]byte(`apiVersion: apps/v1beta1
+		content: []byte(`apiVersion: apps/v1beta1
 kind: Deployment
 metadata:
   name: $NAME-deployment
 `),
+		ignoreUnset: false,
 	}.Render(map[string]interface{}{
 		"NOT_USED": "value",
 	})
@@ -64,3 +66,35 @@ metadata:
 		t.Fatalf("actual: \n%s != expected: \n%s", err.Error(), expected)
 	}
 }
+
+func TestShellTemplateRenderUnresolved(t *testing.T) {
+	actual, err := ShellTemplate{
+		content: []byte(`apiVersion: apps/v1beta1
+kind: Deployment
+metadata:
+  name: $NAME-deployment
+  annotations:
+    replicas-as-string: "${REPLICAS}" # $ $$ test
+spec:
+  replicas: $REPLICAS
+`),
+		ignoreUnset: true,
+	}.Render(map[string]interface{}{
+		"NAME": "app",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	expected := `apiVersion: apps/v1beta1
+kind: Deployment
+metadata:
+  name: app-deployment
+  annotations:
+    replicas-as-string: "${REPLICAS}" # $ $ test
+spec:
+  replicas: $REPLICAS
+`
+	if string(actual) != expected {
+		t.Fatalf("actual: \n%s != expected: \n%s", string(actual), expected)
+	}
+}

kubetpl.go

@@ -53,7 +53,7 @@ func main() {
 	}
 	var syntax, chroot string
 	var configFiles, configKeyValuePairs, freezeRefs, freezeList []string
-	var allowFsAccess, freeze bool
+	var allowFsAccess, ignoreUnset, freeze bool
 	rootCmd := &cobra.Command{
 		Use:  "kubetpl",
 		Long: "Kubernetes templates made easy (https://github.com/shyiko/kubetpl).",
@@ -133,6 +133,7 @@ func main() {
 				freeze:            freeze,
 				freezeRefs:        freezeRefs,
 				freezeList:        normalizedFreezeList,
+				ignoreUnset:       ignoreUnset,
 			})
 			if err != nil {
 				log.Fatal(err)
@@ -153,6 +154,7 @@ func main() {
 			"  kubetpl render template.yml -i staging.env -s KEY=VALUE",
 	}
 	renderCmd.Flags().BoolVarP(&freeze, "freeze", "z", false, "Freeze ConfigMap/Secret|s")
+	renderCmd.Flags().BoolVar(&ignoreUnset, "ignore-unset", false, "Keep $VAR/${VAR} if not set (e.g. \"echo 'kind: $A$B' | kubetpl r - -s A=X --syntax=$ --ignore-unset\" prints \"kind: X$B\")")
 	renderCmd.Flags().StringArrayVar(&freezeRefs, "freeze-ref", nil,
 		"External ConfigMap/Secret|s that should not be included in the output and yet references to which need to be '--freeze'd")
 	renderCmd.Flags().StringSliceVar(&freezeList, "freeze-list", nil,
@@ -265,6 +267,7 @@ type renderOpts struct {
 	freeze            bool
 	freezeRefs        []string
 	freezeList        []string
+	ignoreUnset       bool
 }
 
 func render(templateFiles []string, data map[string]interface{}, opts renderOpts) ([]byte, error) {
@@ -349,7 +352,7 @@ func renderTemplates(templateFiles []string, config map[string]interface{}, opts
 }
 
 func renderTemplate(templateFile string, config map[string]interface{}, opts renderOpts) ([]document, error) {
-	t, directives, err := newTemplate(templateFile, opts.format)
+	t, directives, err := newTemplate(templateFile, opts.format, opts.ignoreUnset)
 	if err != nil {
 		return nil, err
 	}
@@ -425,7 +428,7 @@ func dirnameAbs(path string) (string, error) {
 	return filepath.Abs(filepath.Dir(path))
 }
 
-func newTemplate(file string, flavor string) (engine.Template, []directive, error) {
+func newTemplate(file string, flavor string, ignoreUnset bool) (engine.Template, []directive, error) {
 	content, err := readFile(file)
 	if err != nil {
 		return nil, nil, err
@@ -455,7 +458,11 @@ func newTemplate(file string, flavor string) (engine.Template, []directive, erro
 	var t engine.Template
 	switch flavor {
 	case "$":
-		t, err = engine.NewShellTemplate(content)
+		var opts []engine.ShellTemplateOption
+		if ignoreUnset {
+			opts = append(opts, engine.ShellTemplateIgnoreUnset())
+		}
+		t, err = engine.NewShellTemplate(content, opts...)
 	case "go-template":
 		t, err = engine.NewGoTemplate(content, file)
 	case "template-kind":