From 653c9fcce692a9407e433b4e3ae5c8adf1a33f74 Mon Sep 17 00:00:00 2001
From: Sebastien Ros <sebastienros@gmail.com>
Date: Tue, 10 Jun 2025 15:43:38 -0700
Subject: [PATCH] Consume decimal separator when accepted

---
 src/Parlot/Scanner.cs             |  4 ++--
 test/Parlot.Tests/ScannerTests.cs | 26 +++++++++++++++++++++++---
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/src/Parlot/Scanner.cs b/src/Parlot/Scanner.cs
index b22fa31..343acff 100644
--- a/src/Parlot/Scanner.cs
+++ b/src/Parlot/Scanner.cs
@@ -201,11 +201,11 @@ public bool ReadDecimal(bool allowLeadingSign, bool allowDecimalSeparator, bool
 
             if (!ReadInteger(out number))
             {
-                Cursor.ResetPosition(beforeDecimalSeparator);
-
                 // A decimal separator must be followed by a number if there is no integral part, e.g. `[NaN].[NaN]`
                 if (numberIsEmpty)
                 {
+                    Cursor.ResetPosition(beforeDecimalSeparator);
+
                     return false;
                 }
 
diff --git a/test/Parlot.Tests/ScannerTests.cs b/test/Parlot.Tests/ScannerTests.cs
index b69e096..08510dd 100644
--- a/test/Parlot.Tests/ScannerTests.cs
+++ b/test/Parlot.Tests/ScannerTests.cs
@@ -1,7 +1,7 @@
 using Parlot.Tests.Calc;
 using System;
 using System.Buffers;
-
+using System.Globalization;
 using Xunit;
 
 namespace Parlot.Tests;
@@ -401,14 +401,34 @@ public void ShouldReadDecimalWithGroupSeparator(string input, string expected)
     [Theory]
     [InlineData("123.456", "123.456")]
     [InlineData("123.456a", "123.456")]
-    [InlineData("123.a", "123")]
+    [InlineData("123.a", "123.")]
     [InlineData("123.456.789", "123.456")]
-    [InlineData("123.", "123")]
+    [InlineData("123.", "123.")]
     public void ShouldReadDecimalWithDecimalSeparator(string input, string expected)
     {
         Scanner s = new(input);
 
         Assert.True(s.ReadDecimal(Fluent.NumberOptions.AllowDecimalSeparator, out var result, decimalSeparator: '.'));
+        Assert.True(decimal.TryParse(expected, NumberStyles.Float, CultureInfo.InvariantCulture, out _));
+        Assert.Equal(expected, result);
+    }
+
+    [Theory]
+    [InlineData("123.456", "123")]
+    [InlineData("123.456a", "123")]
+    [InlineData("123.a", "123")]
+    [InlineData("123.456.789", "123")]
+    [InlineData("123.", "123")]
+    [InlineData("123.e", "123")]
+    [InlineData("123.e1", "123")]
+    [InlineData("123e", "123")]
+    [InlineData("123e1", "123e1")]
+    public void ShouldReadIntegerWithExponent(string input, string expected)
+    {
+        Scanner s = new(input);
+
+        Assert.True(s.ReadDecimal(Fluent.NumberOptions.Integer | Fluent.NumberOptions.AllowExponent, out var result, decimalSeparator: '.'));
+        Assert.True(decimal.TryParse(expected, NumberStyles.AllowExponent, CultureInfo.InvariantCulture, out _));
         Assert.Equal(expected, result);
     }
 }