close #19

src/rocker/template/README.md

@@ -58,6 +58,21 @@ This template will yield:
 RUN $'hello\nworld'
 ```
 
+### {{ yaml *anything* }} or {{ *anything* | yaml }}
+Marshals given input to YAML.
+
+Example:
+```
+{{ .Env | yaml }}
+```
+
+This template will yield:
+```
+USER: johnsnow
+DOCKER_MACHINE_NAME: dev
+PATH: /usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin
+```
+
 ### {{ dump *anything* }}
 Pretty-prints any variable. Useful for debugging.
 

src/rocker/template/template.go

@@ -28,6 +28,7 @@ import (
 	"strings"
 	"text/template"
 
+	"github.com/go-yaml/yaml"
 	"github.com/kr/pretty"
 )
 
@@ -54,6 +55,7 @@ func ProcessConfigTemplate(name string, reader io.Reader, vars Vars, funcs map[s
 		"assert":  assertFn,
 		"json":    jsonFn,
 		"shell":   EscapeShellarg,
+		"yaml":    yamlFn,
 	}
 	for k, f := range funcs {
 		funcMap[k] = f
@@ -166,6 +168,14 @@ func jsonFn(v interface{}) (string, error) {
 	return string(data), nil
 }
 
+func yamlFn(v interface{}) (string, error) {
+	data, err := yaml.Marshal(v)
+	if err != nil {
+		return "", err
+	}
+	return string(data), nil
+}
+
 func interfaceToInt(v interface{}) (int, error) {
 	switch v.(type) {
 	case int:

src/rocker/template/template_test.go

@@ -110,6 +110,12 @@ func TestProcessConfigTemplate_Shellarg(t *testing.T) {
 	assert.Equal(t, "echo 'hello world'", processTemplate(t, "echo {{ \"hello world\" | shell }}"))
 }
 
+func TestProcessConfigTemplate_Yaml(t *testing.T) {
+	assert.Equal(t, "key: foo: bar\n", processTemplate(t, "key: {{ .data | yaml }}"))
+	assert.Equal(t, "key: myval\n", processTemplate(t, "key: {{ .mykey | yaml }}"))
+	assert.Equal(t, "key: |-\n  hello\n  world\n", processTemplate(t, "key: {{ \"hello\\nworld\" | yaml }}"))
+}
+
 func processTemplate(t *testing.T, tpl string) string {
 	result, err := ProcessConfigTemplate("test", strings.NewReader(tpl), configTemplateVars, map[string]interface{}{})
 	if err != nil {