The utpl script language supports declaring objects (dictionaries) using
either JSON or JavaScript notation.

-- Expect stdout --
{ }
{ "name": "Bob", "age": 31, "email": { "work": "bob@example.com", "private": "bob@example.org" } }
{ "banana": "yellow", "tomato": "red", "broccoli": "green" }
{ "foo": "bar", "complex key": "qrx" }
{ "foo": { "bar": true } }
-- End --

-- Testcase --
{%
	// An empty object can be declared using a pair of curly brackets
	empty_obj = { };

	// It is also possible to use JSON notation to declare an object
	json_obj = {
		"name": "Bob",
		"age": 31,
		"email": {
			"work": "bob@example.com",
			"private": "bob@example.org"
		}
	};

	// Declaring an object in JavaScript notation is supported as well
	another_obj = {
		banana: "yellow",
		tomato: "red",
		broccoli: "green"
	};

	// Mixing styles is allowed too
	third_obj = {
		foo: "bar",
		"complex key": "qrx"
	};

	// Important caveat: when nesting objects, ensure that curly brackets
	// are separated by space or newline to avoid interpretation as
	// expression block tag!
	nested_obj = { foo: { bar: true } }; // <-- mind the space in "} }"

	// Printing (or stringifying) objects will return their JSON representation
	print(empty_obj, "\n");
	print(json_obj, "\n");
	print(another_obj, "\n");
	print(third_obj, "\n");
	print(nested_obj, "\n");
%}
-- End --


Additionally, utpl implements ES6-like spread operators to allow shallow copying
of object properties into other objects.

-- Expect stdout --
{ "foo": true, "bar": false }
{ "foo": true, "bar": false, "baz": 123, "qrx": 456 }
{ "foo": false, "bar": true, "baz": 123, "qrx": 456 }
{ "foo": true, "bar": false }
{ "foo": true, "bar": false, "level2": { "baz": 123, "qrx": 456 } }
{ "foo": true, "bar": false, "0": 7, "1": 8, "2": 9 }
-- End --

-- Testcase --
{%
	o1 = { foo: true, bar: false };
	o2 = { baz: 123, qrx: 456 };
	arr = [7, 8, 9];

	print(join("\n", [
		// copying one object into another
		{ ...o1 },

		// combining two objects
		{ ...o1, ...o2 },

		// copying object and override properties
		{ ...o1, ...o2, foo: false, bar: true },

		// default properties overwritten by spread operator
		{ foo: 123, bar: 456, ...o1 },

		// nested spread operators
		{ ...o1, level2: { ...o2 } },

		// merging array into objects
		{ ...o1, ...arr }
	]), "\n");
%}
-- End --


ES2015 short hand property notation is supported as well.

-- Expect stdout --
{ "a": 123, "b": true, "c": "test" }
-- End --

-- Testcase --
{%
	a = 123;
	b = true;
	c = "test";

	o = { a, b, c };

	print(o, "\n");
%}
-- End --

-- Expect stderr --
Syntax error: Unexpected token
Expecting ':'
In line 2, byte 14:

 `    o = { "foo" };`
  Near here ------^


-- End --

-- Testcase --
{%
	o = { "foo" };
%}
-- End --

-- Expect stderr --
Syntax error: Invalid identifier
In line 2, byte 8:

 `    o = { function };`
            ^-- Near here


-- End --

-- Testcase --
{%
	o = { function };
%}
-- End --


ES2015 computed property names are supported.

-- Expect stdout --
{ "test": true, "hello": false, "ABC": 123 }
-- End --

-- Testcase --
{%
	s = "test";
	o = {
		[s]: true,
		["he" + "llo"]: false,
		[uc("abc")]: 123
	};

	print(o, "\n");
%}
-- End --

-- Expect stderr --
Syntax error: Expecting expression
In line 2, byte 10:

 `    o1 = { []: true };`
  Near here --^


Syntax error: Unexpected token
Expecting ']'
In line 3, byte 14:

 `    o2 = { [true, false]: 123 };`
  Near here ------^


-- End --

-- Testcase --
{%
	o1 = { []: true };
	o2 = { [true, false]: 123 };
%}
-- End --