Improve decimals scale calculation on net8.0 (#807)

Improve number formatting based on Shopify's implementation

Author: sebastienros

Fluid.Tests/ParserTests.cs

@@ -516,6 +516,51 @@ public void ShouldChangeVariableType(string source, string expected)
             Assert.Equal(expected, rendered);
         }
 
+        [Theory]
+        [InlineData("{{ 0 | times: 1 }}", "0")]
+        [InlineData("{{ 0.0 | times: 1 }}", "0.0")]
+        [InlineData("{{ 0.1 | times: 1 }}", "0.1")]
+        [InlineData("{{ 0.01 | times: 1 }}", "0.01")]
+        [InlineData("{{ 0.0123 | times: 1 }}", "0.0123")]
+        [InlineData("{{ 0 | times: 1.0 }}", "0.0")]
+        [InlineData("{{ 1 | times: 1 }}", "1")]
+        [InlineData("{{ 1 | times: 1.1 }}", "1.1")]
+        [InlineData("{{ 1 | times: 1.123 }}", "1.123")]
+        [InlineData("{{ 1 | times: 1.1234567890 }}", "1.123456789")]
+        [InlineData("{{ 1 | times: 1.1000 }}", "1.1")]
+        [InlineData("{{ 1.1000 | times: 1 }}", "1.1")]
+        [InlineData("{{ 1 | times: 1. }}", "1")]
+        public void ShouldPreservePrecision(string source, string expected)
+        {
+            var result = _parser.TryParse(source, out var template, out var errors);
+
+            Assert.True(result);
+            Assert.NotNull(template);
+            Assert.Null(errors);
+
+            var rendered = template.Render();
+
+            Assert.Equal(expected, rendered);
+        }
+
+        [Theory]
+        [InlineData("{{ 0. | times: 1 }}", "0")]
+        [InlineData("{{ 0.0 | times: 1.0 }}", "0.0")]
+        [InlineData("{{ 0.00 | times: 1 }}", "0.0")]
+        [InlineData("{{ 0. | times: 1.0 }}", "0.0")]
+        public void DotsAreParsedAsIntegralValues(string source, string expected)
+        {
+            var result = _parser.TryParse(source, out var template, out var errors);
+
+            Assert.True(result);
+            Assert.NotNull(template);
+            Assert.Null(errors);
+
+            var rendered = template.Render();
+
+            Assert.Equal(expected, rendered);
+        }
+
         [Theory]
         [InlineData("{% assign my_string = 'abcd' %}{{ my_string.size }}", "4")]
         public void SizeAppliedToStrings(string source, string expected)

Fluid/Values/NumberValue.cs

@@ -68,8 +68,26 @@ public override void WriteTo(TextWriter writer, TextEncoder encoder, CultureInfo
         public override ValueTask WriteToAsync(TextWriter writer, TextEncoder encoder, CultureInfo cultureInfo)
         {
             AssertWriteToParameters(writer, encoder, cultureInfo);
-            var task = writer.WriteAsync(encoder.Encode(_value.ToString(cultureInfo)));
 
+            Task task = default;
+
+            var scale = GetScale(_value);
+            if (scale == 0)
+            {
+                // If the scale is zero, we can write the value directly without formatting
+                task = writer.WriteAsync(encoder.Encode(_value.ToString(cultureInfo)));
+            }
+            else if (_value * (10 * scale) % (10 * scale) == 0)
+            {
+                // If the decimal part is zero(s), write one only
+                task = writer.WriteAsync(encoder.Encode(_value.ToString("F1", cultureInfo)));
+            }
+            else
+            {
+                // For larger scales, we use G29 to avoid trailing zeros
+                task = writer.WriteAsync(encoder.Encode(_value.ToString("G29", cultureInfo)));
+            }
+            
             if (task.IsCompletedSuccessfully())
             {
                 return default;
@@ -149,16 +167,16 @@ internal static NumberValue Create(int value)
             return new NumberValue(value);
         }
 
-        public static int GetScale(decimal value)
+        /// <summary>
+        /// Gets the scale of a decimal value, which is the number of digits to the right of the decimal point.
+        /// </summary>
+        public static byte GetScale(decimal value)
         {
-            if (value == 0)
-            {
-                return 0;
-            }
-
-            var bits = decimal.GetBits(value);
-
-            return (int)((bits[3] >> 16) & 0x7F);
+#if NET8_0_OR_GREATER
+            return value.Scale;
+#else       
+            return unchecked((byte)(decimal.GetBits(value)[3] >> 16));
+#endif
         }
     }
 }