Fix calc() computation in trimmed / NativeAOT applications

src/AngleSharp.Css.Tests/Values/Calc.cs

@@ -1,8 +1,13 @@
+#nullable disable
 namespace AngleSharp.Css.Tests.Values
 {
+    using AngleSharp.Css.Dom;
     using AngleSharp.Css.Parser;
+    using AngleSharp.Css.Values;
+    using AngleSharp.Dom;
     using AngleSharp.Text;
     using NUnit.Framework;
+    using System;
     using static CssConstructionFunctions;
 
     [TestFixture]
@@ -100,5 +105,47 @@ public void IntegerCanBeUsedWithCalc()
             Assert.IsTrue(property.HasValue);
             Assert.AreEqual("calc(21 + 5 - 4 * 2)", property.Value);
         }
+
+        [Test]
+        public void CalcAdditionOfLengthsIsComputed()
+        {
+            var document = ParseDocument("<style>p { width: calc(100px + 20px) }</style><p></p>");
+            var style = document.QuerySelector("p").ComputeCurrentStyle();
+            Assert.AreEqual("120px", style.GetWidth());
+        }
+
+        [Test]
+        public void CalcSubtractionOfLengthsIsComputed()
+        {
+            var document = ParseDocument("<style>p { width: calc(100px - 20px) }</style><p></p>");
+            var style = document.QuerySelector("p").ComputeCurrentStyle();
+            Assert.AreEqual("80px", style.GetWidth());
+        }
+
+        [Test]
+        public void CalcAdditionOfTimesIsComputed()
+        {
+            var document = ParseDocument("<style>p { transition-duration: calc(30ms + 20ms) }</style><p></p>");
+            var style = document.QuerySelector("p").ComputeCurrentStyle();
+            Assert.AreEqual("50ms", style.GetTransitionDuration());
+        }
+
+        [TestCase(typeof(CssAngleValue))]
+        [TestCase(typeof(CssFrequencyValue))]
+        [TestCase(typeof(CssIntegerValue))]
+        [TestCase(typeof(CssLengthValue))]
+        [TestCase(typeof(CssNumberValue))]
+        [TestCase(typeof(CssPercentageValue))]
+        [TestCase(typeof(CssResolutionValue))]
+        [TestCase(typeof(CssTimeValue))]
+        public void MetricValueCanBeCreatedWithAnotherValue(Type type)
+        {
+            var template = (ICssMetricValue)Activator.CreateInstance(type, 2.0);
+            var result = template.WithValue(5.0);
+
+            Assert.IsInstanceOf(type, result);
+            Assert.AreEqual(5.0, ((ICssMetricValue)result).Value);
+            Assert.AreEqual(template.UnitString, ((ICssMetricValue)result).UnitString);
+        }
     }
 }

src/AngleSharp.Css/Extensions/CssMetricValueExtensions.cs

@@ -0,0 +1,39 @@
+#nullable disable
+namespace AngleSharp.Css.Values
+{
+    using AngleSharp.Css.Dom;
+    using System;
+#if NET5_0_OR_GREATER
+    using System.Diagnostics.CodeAnalysis;
+#endif
+
+    /// <summary>
+    /// A set of helpers for dealing with metric values.
+    /// </summary>
+    static class CssMetricValueExtensions
+    {
+        /// <summary>
+        /// Creates a new metric value of the same type as the given template, but
+        /// carrying the provided value.
+        /// </summary>
+        /// <param name="template">The value determining the type to create.</param>
+        /// <param name="value">The value to use for the created instance.</param>
+        /// <returns>The newly created metric value.</returns>
+#if NET5_0_OR_GREATER
+        [DynamicDependency(DynamicallyAccessedMemberTypes.PublicConstructors, typeof(CssAngleValue))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.PublicConstructors, typeof(CssFrequencyValue))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.PublicConstructors, typeof(CssIntegerValue))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.PublicConstructors, typeof(CssLengthValue))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.PublicConstructors, typeof(CssNumberValue))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.PublicConstructors, typeof(CssPercentageValue))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.PublicConstructors, typeof(CssResolutionValue))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.PublicConstructors, typeof(CssTimeValue))]
+        [UnconditionalSuppressMessage("Trimming", "IL2072",
+            Justification = "The constructors of the metric values shipped with AngleSharp.Css are preserved via " +
+                "DynamicDependency. Metric values implemented outside of AngleSharp.Css have to preserve their " +
+                "public constructor taking a single Double themselves, e.g., via DynamicDependency.")]
+#endif
+        public static ICssValue WithValue(this ICssMetricValue template, Double value) =>
+            (ICssValue)Activator.CreateInstance(template.GetType(), value);
+    }
+}

src/AngleSharp.Css/Values/Expressions/CssCalcAddExpression.cs

@@ -60,7 +60,7 @@ ICssValue ICssValue.Compute(ICssComputeContext context)
             if (left is ICssMetricValue x && right is ICssMetricValue y && x.UnitString == y.UnitString)
             {
                 var result = x.Value + y.Value;
-                return (ICssValue)Activator.CreateInstance(x.GetType(), result);
+                return x.WithValue(result);
             }
 
             return null;

src/AngleSharp.Css/Values/Expressions/CssCalcDivExpression.cs

@@ -60,7 +60,7 @@ ICssValue ICssValue.Compute(ICssComputeContext context)
             if (left is ICssMetricValue x && right is ICssMetricValue y && x.UnitString == y.UnitString)
             {
                 var result = x.Value / y.Value;
-                return (ICssValue)Activator.CreateInstance(x.GetType(), result);
+                return x.WithValue(result);
             }
 
             return null;

src/AngleSharp.Css/Values/Expressions/CssCalcMulExpression.cs

@@ -60,7 +60,7 @@ ICssValue ICssValue.Compute(ICssComputeContext context)
             if (left is ICssMetricValue x && right is ICssMetricValue y && x.UnitString == y.UnitString)
             {
                 var result = x.Value * y.Value;
-                return (ICssValue)Activator.CreateInstance(x.GetType(), result);
+                return x.WithValue(result);
             }
 
             return null;

src/AngleSharp.Css/Values/Expressions/CssCalcSubExpression.cs

@@ -60,7 +60,7 @@ ICssValue ICssValue.Compute(ICssComputeContext context)
             if (left is ICssMetricValue x && right is ICssMetricValue y && x.UnitString == y.UnitString)
             {
                 var result = x.Value - y.Value;
-                return (ICssValue)Activator.CreateInstance(x.GetType(), result);
+                return x.WithValue(result);
             }
 
             return null;