config: jsonencode function to support nested lists and maps

config/interpolate_funcs.go

@@ -824,8 +824,7 @@ func interpolationFuncJoin() ast.Function {
 }
 
 // interpolationFuncJSONEncode implements the "jsonencode" function that encodes
-// a string, list, or map as its JSON representation. For now, values in the
-// list or map may only be strings.
+// a string, list, or map as its JSON representation.
 func interpolationFuncJSONEncode() ast.Function {
 	return ast.Function{
 		ArgTypes:   []ast.Type{ast.TypeAny},
@@ -838,28 +837,36 @@ func interpolationFuncJSONEncode() ast.Function {
 				toEncode = typedArg
 
 			case []ast.Variable:
-				// We preallocate the list here. Note that it's important that in
-				// the length 0 case, we have an empty list rather than nil, as
-				// they encode differently.
-				// XXX It would be nice to support arbitrarily nested data here. Is
-				// there an inverse of hil.InterfaceToVariable?
 				strings := make([]string, len(typedArg))
 
 				for i, v := range typedArg {
 					if v.Type != ast.TypeString {
-						return "", fmt.Errorf("list elements must be strings")
+						variable, _ := hil.InterfaceToVariable(typedArg)
+						toEncode, _ = hil.VariableToInterface(variable)
+
+						jEnc, err := json.Marshal(toEncode)
+						if err != nil {
+							return "", fmt.Errorf("failed to encode JSON data '%s'", toEncode)
+						}
+						return string(jEnc), nil
+
 					}
 					strings[i] = v.Value.(string)
 				}
 				toEncode = strings
 
 			case map[string]ast.Variable:
-				// XXX It would be nice to support arbitrarily nested data here. Is
-				// there an inverse of hil.InterfaceToVariable?
 				stringMap := make(map[string]string)
 				for k, v := range typedArg {
 					if v.Type != ast.TypeString {
-						return "", fmt.Errorf("map values must be strings")
+						variable, _ := hil.InterfaceToVariable(typedArg)
+						toEncode, _ = hil.VariableToInterface(variable)
+
+						jEnc, err := json.Marshal(toEncode)
+						if err != nil {
+							return "", fmt.Errorf("failed to encode JSON data '%s'", toEncode)
+						}
+						return string(jEnc), nil
 					}
 					stringMap[k] = v.Value.(string)
 				}

config/interpolate_funcs_test.go

@@ -1406,8 +1406,6 @@ func TestInterpolateFuncJSONEncode(t *testing.T) {
 				Type:  ast.TypeString,
 			},
 			"list": interfaceToVariableSwallowError([]string{"foo", "bar\tbaz"}),
-			// XXX can't use InterfaceToVariable as it converts empty slice into empty
-			// map.
 			"emptylist": ast.Variable{
 				Value: []ast.Variable{},
 				Type:  ast.TypeList,
@@ -1416,9 +1414,7 @@ func TestInterpolateFuncJSONEncode(t *testing.T) {
 				"foo":     "bar",
 				"ba \n z": "q\\x",
 			}),
-			"emptymap": interfaceToVariableSwallowError(map[string]string{}),
-
-			// Not yet supported (but it would be nice)
+			"emptymap":   interfaceToVariableSwallowError(map[string]string{}),
 			"nestedlist": interfaceToVariableSwallowError([][]string{{"foo"}}),
 			"nestedmap":  interfaceToVariableSwallowError(map[string][]string{"foo": {"bar"}}),
 		},
@@ -1470,13 +1466,13 @@ func TestInterpolateFuncJSONEncode(t *testing.T) {
 			},
 			{
 				`${jsonencode(nestedlist)}`,
-				nil,
-				true,
+				`[["foo"]]`,
+				false,
 			},
 			{
 				`${jsonencode(nestedmap)}`,
-				nil,
-				true,
+				`{"foo":["bar"]}`,
+				false,
 			},
 		},
 	})

website/docs/configuration/interpolation.html.md

@@ -262,10 +262,9 @@ The supported built-in functions are:
       * `join(",", aws_instance.foo.*.id)`
       * `join(",", var.ami_list)`
 
-  * `jsonencode(item)` - Returns a JSON-encoded representation of the given
-    item, which may be a string, list of strings, or map from string to string.
-    Note that if the item is a string, the return value includes the double
-    quotes.
+  * `jsonencode(value)` - Returns a JSON-encoded representation of the given
+      value, which can contain arbitrarily-nested lists and maps. Note that if
+      the value is a string then its value will be placed in quotes.
 
   * `keys(map)` - Returns a lexically sorted list of the map keys.