Add a test suite for JSON

This test suite doesn't attempt to test error/invalid cases since
the current JSON parser has a lot of false negatives.

tests/test_json.h

@@ -0,0 +1,167 @@
+/*************************************************************************/
+/*  test_json.h                                                          */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#ifndef TEST_JSON_H
+#define TEST_JSON_H
+
+#include "core/io/json.h"
+
+#include "thirdparty/doctest/doctest.h"
+
+namespace TestJSON {
+
+// NOTE: The current JSON parser accepts many non-conformant strings such as
+// single-quoted strings, duplicate commas and trailing commas.
+// This is intentionally not tested as users shouldn't rely on this behavior.
+
+TEST_CASE("[JSON] Parsing single data types") {
+	// Parsing a single data type as JSON is valid per the JSON specification.
+
+	JSON json;
+	Variant result;
+	String err_str;
+	int err_line;
+
+	json.parse("null", result, err_str, err_line);
+	CHECK_MESSAGE(
+			err_line == 0,
+			"Parsing `null` as JSON should parse successfully.");
+	CHECK_MESSAGE(
+			result == Variant(),
+			"Parsing a double quoted string as JSON should return the expected value.");
+
+	json.parse("true", result, err_str, err_line);
+	CHECK_MESSAGE(
+			err_line == 0,
+			"Parsing boolean `true` as JSON should parse successfully.");
+	CHECK_MESSAGE(
+			result,
+			"Parsing boolean `true` as JSON should return the expected value.");
+
+	json.parse("false", result, err_str, err_line);
+	CHECK_MESSAGE(
+			err_line == 0,
+			"Parsing boolean `false` as JSON should parse successfully.");
+	CHECK_MESSAGE(
+			!result,
+			"Parsing boolean `false` as JSON should return the expected value.");
+
+	// JSON only has a floating-point number type, no integer type.
+	// This is why we use `is_equal_approx()` for the comparison.
+	json.parse("123456", result, err_str, err_line);
+	CHECK_MESSAGE(
+			err_line == 0,
+			"Parsing an integer number as JSON should parse successfully.");
+	CHECK_MESSAGE(
+			Math::is_equal_approx(result, 123'456),
+			"Parsing an integer number as JSON should return the expected value.");
+
+	json.parse("0.123456", result, err_str, err_line);
+	CHECK_MESSAGE(
+			err_line == 0,
+			"Parsing a floating-point number as JSON should parse successfully.");
+	CHECK_MESSAGE(
+			Math::is_equal_approx(result, 0.123456),
+			"Parsing a floating-point number as JSON should return the expected value.");
+
+	json.parse("\"hello\"", result, err_str, err_line);
+	CHECK_MESSAGE(
+			err_line == 0,
+			"Parsing a double quoted string as JSON should parse successfully.");
+	CHECK_MESSAGE(
+			result == "hello",
+			"Parsing a double quoted string as JSON should return the expected value.");
+}
+
+TEST_CASE("[JSON] Parsing arrays") {
+	JSON json;
+	Variant result;
+	String err_str;
+	int err_line;
+
+	// JSON parsing fails if it's split over several lines (even if leading indentation is removed).
+	json.parse(
+			R"(["Hello", "world.", "This is",["a","json","array.",[]], "Empty arrays ahoy:", [[["Gotcha!"]]]])",
+			result, err_str, err_line);
+
+	const Array array = result;
+	CHECK_MESSAGE(
+			err_line == 0,
+			"Parsing a JSON array should parse successfully.");
+	CHECK_MESSAGE(
+			array[0] == "Hello",
+			"The parsed JSON should contain the expected values.");
+	const Array sub_array = array[3];
+	CHECK_MESSAGE(
+			sub_array.size() == 4,
+			"The parsed JSON should contain the expected values.");
+	CHECK_MESSAGE(
+			sub_array[1] == "json",
+			"The parsed JSON should contain the expected values.");
+	CHECK_MESSAGE(
+			sub_array[3].hash() == Array().hash(),
+			"The parsed JSON should contain the expected values.");
+	const Array deep_array = Array(Array(array[5])[0])[0];
+	CHECK_MESSAGE(
+			deep_array[0] == "Gotcha!",
+			"The parsed JSON should contain the expected values.");
+}
+
+TEST_CASE("[JSON] Parsing objects (dictionaries)") {
+	JSON json;
+	Variant result;
+	String err_str;
+	int err_line;
+
+	json.parse(
+			R"({"name": "Godot Engine", "is_free": true, "bugs": null, "apples": {"red": 500, "green": 0, "blue": -20}, "empty_object": {}})",
+			result, err_str, err_line);
+
+	const Dictionary dictionary = result;
+	CHECK_MESSAGE(
+			dictionary["name"] == "Godot Engine",
+			"The parsed JSON should contain the expected values.");
+	CHECK_MESSAGE(
+			dictionary["is_free"],
+			"The parsed JSON should contain the expected values.");
+	CHECK_MESSAGE(
+			dictionary["bugs"] == Variant(),
+			"The parsed JSON should contain the expected values.");
+	CHECK_MESSAGE(
+			Math::is_equal_approx(Dictionary(dictionary["apples"])["blue"], -20),
+			"The parsed JSON should contain the expected values.");
+	CHECK_MESSAGE(
+			dictionary["empty_object"].hash() == Dictionary().hash(),
+			"The parsed JSON should contain the expected values.");
+}
+
+} // namespace TestJSON
+
+#endif // TEST_JSON_H

tests/test_main.cpp

@@ -40,6 +40,7 @@
 #include "test_expression.h"
 #include "test_gradient.h"
 #include "test_gui.h"
+#include "test_json.h"
 #include "test_list.h"
 #include "test_math.h"
 #include "test_method_bind.h"