From 1d790deedb53c5b7f82ab225c74829284436484a Mon Sep 17 00:00:00 2001
From: Haoyu Qiu <timothyqiu32@gmail.com>
Date: Tue, 2 Jul 2024 17:12:21 +0800
Subject: [PATCH] Fix parsing of `4.` in Expression

(cherry picked from commit ee9cea521d97088eb368cb1820db71100da9837b)
---
 core/math/expression.cpp          | 10 ++----
 tests/core/math/test_expression.h | 53 +++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+), 7 deletions(-)

diff --git a/core/math/expression.cpp b/core/math/expression.cpp
index 636c2c16bf3..0692ece1e6f 100644
--- a/core/math/expression.cpp
+++ b/core/math/expression.cpp
@@ -30,12 +30,7 @@
 
 #include "expression.h"
 
-#include "core/io/marshalls.h"
-#include "core/math/math_funcs.h"
 #include "core/object/class_db.h"
-#include "core/object/ref_counted.h"
-#include "core/os/os.h"
-#include "core/variant/variant_parser.h"
 
 Error Expression::_get_token(Token &r_token) {
 	while (true) {
@@ -392,7 +387,6 @@ Error Expression::_get_token(Token &r_token) {
 								if (is_digit(c)) {
 								} else if (c == 'e') {
 									reading = READING_EXP;
-
 								} else {
 									reading = READING_DONE;
 								}
@@ -419,7 +413,9 @@ Error Expression::_get_token(Token &r_token) {
 						is_first_char = false;
 					}
 
-					str_ofs--;
+					if (c != 0) {
+						str_ofs--;
+					}
 
 					r_token.type = TK_CONSTANT;
 
diff --git a/tests/core/math/test_expression.h b/tests/core/math/test_expression.h
index 512d7932f9a..c3e42804919 100644
--- a/tests/core/math/test_expression.h
+++ b/tests/core/math/test_expression.h
@@ -122,6 +122,59 @@ TEST_CASE("[Expression] Floating-point arithmetic") {
 			"Float multiplication-addition-subtraction-division should return the expected result.");
 }
 
+TEST_CASE("[Expression] Floating-point notation") {
+	Expression expression;
+
+	CHECK_MESSAGE(
+			expression.parse("2.") == OK,
+			"The expression should parse successfully.");
+	CHECK_MESSAGE(
+			double(expression.execute()) == doctest::Approx(2.0),
+			"The expression should return the expected result.");
+
+	CHECK_MESSAGE(
+			expression.parse("(2.)") == OK,
+			"The expression should parse successfully.");
+	CHECK_MESSAGE(
+			double(expression.execute()) == doctest::Approx(2.0),
+			"The expression should return the expected result.");
+
+	CHECK_MESSAGE(
+			expression.parse(".3") == OK,
+			"The expression should parse successfully.");
+	CHECK_MESSAGE(
+			double(expression.execute()) == doctest::Approx(0.3),
+			"The expression should return the expected result.");
+
+	CHECK_MESSAGE(
+			expression.parse("2.+5.") == OK,
+			"The expression should parse successfully.");
+	CHECK_MESSAGE(
+			double(expression.execute()) == doctest::Approx(7.0),
+			"The expression should return the expected result.");
+
+	CHECK_MESSAGE(
+			expression.parse(".3-.8") == OK,
+			"The expression should parse successfully.");
+	CHECK_MESSAGE(
+			double(expression.execute()) == doctest::Approx(-0.5),
+			"The expression should return the expected result.");
+
+	CHECK_MESSAGE(
+			expression.parse("2.+.2") == OK,
+			"The expression should parse successfully.");
+	CHECK_MESSAGE(
+			double(expression.execute()) == doctest::Approx(2.2),
+			"The expression should return the expected result.");
+
+	CHECK_MESSAGE(
+			expression.parse(".0*0.") == OK,
+			"The expression should parse successfully.");
+	CHECK_MESSAGE(
+			double(expression.execute()) == doctest::Approx(0.0),
+			"The expression should return the expected result.");
+}
+
 TEST_CASE("[Expression] Scientific notation") {
 	Expression expression;