config: new interpolation function jsonencode

config/interpolate_funcs.go

@@ -7,6 +7,7 @@ import (
  "crypto/sha256"
  "encoding/base64"
  "encoding/hex"
+ "encoding/json"
  "errors"
  "fmt"
  "io/ioutil"
@@ -40,6 +41,7 @@ func Funcs() map[string]ast.Function {
  "formatlist": interpolationFuncFormatList(),
  "index": interpolationFuncIndex(),
  "join": interpolationFuncJoin(),
+ "jsonencode": interpolationFuncJSONEncode(),
  "length": interpolationFuncLength(),
  "lower": interpolationFuncLower(),
  "md5": interpolationFuncMd5(),
@@ -364,6 +366,23 @@ func interpolationFuncJoin() ast.Function {
  }
 }
 
+// interpolationFuncJSONEncode implements the "jsonencode" function that encodes
+// a string as its JSON representation.
+func interpolationFuncJSONEncode() ast.Function {
+ return ast.Function{
+ ArgTypes: []ast.Type{ast.TypeString},
+ ReturnType: ast.TypeString,
+ Callback: func(args []interface{}) (interface{}, error) {
+ s := args[0].(string)
+ jEnc, err := json.Marshal(s)
+ if err != nil {
+ return "", fmt.Errorf("failed to encode JSON data '%s'", s)
+ }
+ return string(jEnc), nil
+ },
+ }
+}
+
 // interpolationFuncReplace implements the "replace" function that does
 // string replacement.
 func interpolationFuncReplace() ast.Function {

config/interpolate_funcs_test.go

@@ -437,6 +437,48 @@ func TestInterpolateFuncJoin(t *testing.T) {
  })
 }
 
+func TestInterpolateFuncJSONEncode(t *testing.T) {
+ testFunction(t, testFunctionConfig{
+ Vars: map[string]ast.Variable{
+ "easy": ast.Variable{
+ Value: "test",
+ Type: ast.TypeString,
+ },
+ "hard": ast.Variable{
+ Value: " foo \\ \n \t \" bar ",
+ Type: ast.TypeString,
+ },
+ },
+ Cases: []testFunctionCase{
+ {
+ `${jsonencode("test")}`,
+ `"test"`,
+ false,
+ },
+ {
+ `${jsonencode(easy)}`,
+ `"test"`,
+ false,
+ },
+ {
+ `${jsonencode(hard)}`,
+ `" foo \\ \n \t \" bar "`,
+ false,
+ },
+ {
+ `${jsonencode("")}`,
+ `""`,
+ false,
+ },
+ {
+ `${jsonencode()}`,
+ nil,
+ true,
+ },
+ },
+ })
+}
+
 func TestInterpolateFuncReplace(t *testing.T) {
  testFunction(t, testFunctionConfig{
  Cases: []testFunctionCase{

website/source/docs/configuration/interpolation.html.md

@@ -150,6 +150,9 @@ The supported built-in functions are:
  only possible with splat variables from resources with a count
  greater than one. Example: `join(",", aws_instance.foo.*.id)`
 
+ * `jsonencode(string)` - Returns a JSON-encoded representation of the given
+ string (including double quotes).
+
  * `length(list)` - Returns a number of members in a given list
  or a number of characters in a given string.
  * `${length(split(",", "a,b,c"))}` = 3