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Merged
koenbeuk merged 1 commit into from
May 7, 2026
Merged

Add support for nullable enums in expressive properties #61

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13 changes: 12 additions & 1 deletion src/ExpressiveSharp.Generator/Emitter/ExpressionTreeEmitter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -753,13 +753,25 @@ private bool TryEmitEnumMethodExpansion(IInvocationOperation invocation, out str
AppendLine($"var {defaultVar} = {Expr}.Default(typeof({returnTypeFqn}));");
}

var receiverTypeFqn = receiverType.ToDisplayString(_fqnFormat);

// Build the ternary chain in reverse so the first member ends up as the outermost (and first-tested) branch.
var currentVar = defaultVar;
foreach (var member in enumMembers.AsEnumerable().Reverse())
{
var enumValueVar = NextVar();
AppendLine($"var {enumValueVar} = {Expr}.Constant({enumTypeFqn}.{member.Name}, typeof({enumTypeFqn}));");

// The MethodInfo is bound on the original receiver type — for an instance method on
// Nullable<TEnum> or an extension whose first param is Nullable<TEnum>, the per-arm
// operand must also be Nullable<TEnum> or Expression.Call rejects the type mismatch.
if (isNullable)
{
var lifted = NextVar();
AppendLine($"var {lifted} = {Expr}.Convert({enumValueVar}, typeof({receiverTypeFqn}));");
enumValueVar = lifted;
}

// Static path passes the enum value as the first arg; instance path uses it as the receiver.
string callVar;
if (originalMethod.IsStatic)
Expand Down Expand Up @@ -800,7 +812,6 @@ private bool TryEmitEnumMethodExpansion(IInvocationOperation invocation, out str
if (isNullable)
{
var nullConst = NextVar();
var receiverTypeFqn = receiverType.ToDisplayString(_fqnFormat);
AppendLine($"var {nullConst} = {Expr}.Constant(null, typeof({receiverTypeFqn}));");

var nullCheck = NextVar();
Expand Down
38 changes: 38 additions & 0 deletions ...ator.Tests/ExpressiveGenerator/EnumTests.ExpandExtensionMethodOnNullableEnum.verified.txt
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@@ -0,0 +1,38 @@
// <auto-generated/>
#nullable disable

using Foo;

namespace ExpressiveSharp.Generated
{
static partial class Foo_Entity
{
// [Expressive]
// public string TrendLabel => Trend.Describe();
static global::System.Linq.Expressions.Expression<global::System.Func<global::Foo.Entity, string>> TrendLabel_Expression()
{
var p__this = global::System.Linq.Expressions.Expression.Parameter(typeof(global::Foo.Entity), "@this");
var expr_0 = global::System.Linq.Expressions.Expression.Property(p__this, typeof(global::Foo.Entity).GetProperty("Trend", global::System.Reflection.BindingFlags.Public | global::System.Reflection.BindingFlags.NonPublic | global::System.Reflection.BindingFlags.Instance)); // Trend
var expr_1 = global::System.Linq.Expressions.Expression.Constant(null, typeof(string));
var expr_2 = global::System.Linq.Expressions.Expression.Constant(global::Foo.Trend.NoChange, typeof(global::Foo.Trend));
var expr_3 = global::System.Linq.Expressions.Expression.Convert(expr_2, typeof(global::Foo.Trend?));
var expr_4 = global::System.Linq.Expressions.Expression.Call(typeof(global::Foo.TrendExtensions).GetMethod("Describe", global::System.Reflection.BindingFlags.Public | global::System.Reflection.BindingFlags.NonPublic | global::System.Reflection.BindingFlags.Static, null, new global::System.Type[] { typeof(global::Foo.Trend?) }, null), new global::System.Linq.Expressions.Expression[] { expr_3 });
var expr_5 = global::System.Linq.Expressions.Expression.Equal(expr_0, expr_3);
var expr_6 = global::System.Linq.Expressions.Expression.Condition(expr_5, expr_4, expr_1, typeof(string));
var expr_7 = global::System.Linq.Expressions.Expression.Constant(global::Foo.Trend.Decrease, typeof(global::Foo.Trend));
var expr_8 = global::System.Linq.Expressions.Expression.Convert(expr_7, typeof(global::Foo.Trend?));
var expr_9 = global::System.Linq.Expressions.Expression.Call(typeof(global::Foo.TrendExtensions).GetMethod("Describe", global::System.Reflection.BindingFlags.Public | global::System.Reflection.BindingFlags.NonPublic | global::System.Reflection.BindingFlags.Static, null, new global::System.Type[] { typeof(global::Foo.Trend?) }, null), new global::System.Linq.Expressions.Expression[] { expr_8 });
var expr_10 = global::System.Linq.Expressions.Expression.Equal(expr_0, expr_8);
var expr_11 = global::System.Linq.Expressions.Expression.Condition(expr_10, expr_9, expr_6, typeof(string));
var expr_12 = global::System.Linq.Expressions.Expression.Constant(global::Foo.Trend.Increase, typeof(global::Foo.Trend));
var expr_13 = global::System.Linq.Expressions.Expression.Convert(expr_12, typeof(global::Foo.Trend?));
var expr_14 = global::System.Linq.Expressions.Expression.Call(typeof(global::Foo.TrendExtensions).GetMethod("Describe", global::System.Reflection.BindingFlags.Public | global::System.Reflection.BindingFlags.NonPublic | global::System.Reflection.BindingFlags.Static, null, new global::System.Type[] { typeof(global::Foo.Trend?) }, null), new global::System.Linq.Expressions.Expression[] { expr_13 });
var expr_15 = global::System.Linq.Expressions.Expression.Equal(expr_0, expr_13);
var expr_16 = global::System.Linq.Expressions.Expression.Condition(expr_15, expr_14, expr_11, typeof(string));
var expr_17 = global::System.Linq.Expressions.Expression.Constant(null, typeof(global::Foo.Trend?));
var expr_18 = global::System.Linq.Expressions.Expression.Equal(expr_0, expr_17);
var expr_19 = global::System.Linq.Expressions.Expression.Condition(expr_18, expr_1, expr_16, typeof(string));
return global::System.Linq.Expressions.Expression.Lambda<global::System.Func<global::Foo.Entity, string>>(expr_19, p__this);
}
}
}
40 changes: 40 additions & 0 deletions ...p.Generator.Tests/ExpressiveGenerator/EnumTests.ExpandToStringOnNullableEnum.verified.txt
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@@ -0,0 +1,40 @@
// <auto-generated/>
#nullable disable

using Foo;

namespace ExpressiveSharp.Generated
{
static partial class Foo_Entity
{
// [Expressive]
// public string TrendLabel => Trend.ToString() ?? string.Empty;
static global::System.Linq.Expressions.Expression<global::System.Func<global::Foo.Entity, string>> TrendLabel_Expression()
{
var p__this = global::System.Linq.Expressions.Expression.Parameter(typeof(global::Foo.Entity), "@this");
var expr_1 = global::System.Linq.Expressions.Expression.Property(p__this, typeof(global::Foo.Entity).GetProperty("Trend", global::System.Reflection.BindingFlags.Public | global::System.Reflection.BindingFlags.NonPublic | global::System.Reflection.BindingFlags.Instance)); // Trend
var expr_2 = global::System.Linq.Expressions.Expression.Constant(null, typeof(string));
var expr_3 = global::System.Linq.Expressions.Expression.Constant(global::Foo.Trend.NoChange, typeof(global::Foo.Trend));
var expr_4 = global::System.Linq.Expressions.Expression.Convert(expr_3, typeof(global::Foo.Trend?));
var expr_5 = global::System.Linq.Expressions.Expression.Call(expr_4, typeof(global::Foo.Trend?).GetMethod("ToString", global::System.Reflection.BindingFlags.Public | global::System.Reflection.BindingFlags.NonPublic | global::System.Reflection.BindingFlags.Instance, null, new global::System.Type[] { }, null), global::System.Array.Empty<global::System.Linq.Expressions.Expression>());
var expr_6 = global::System.Linq.Expressions.Expression.Equal(expr_1, expr_4);
var expr_7 = global::System.Linq.Expressions.Expression.Condition(expr_6, expr_5, expr_2, typeof(string));
var expr_8 = global::System.Linq.Expressions.Expression.Constant(global::Foo.Trend.Decrease, typeof(global::Foo.Trend));
var expr_9 = global::System.Linq.Expressions.Expression.Convert(expr_8, typeof(global::Foo.Trend?));
var expr_10 = global::System.Linq.Expressions.Expression.Call(expr_9, typeof(global::Foo.Trend?).GetMethod("ToString", global::System.Reflection.BindingFlags.Public | global::System.Reflection.BindingFlags.NonPublic | global::System.Reflection.BindingFlags.Instance, null, new global::System.Type[] { }, null), global::System.Array.Empty<global::System.Linq.Expressions.Expression>());
var expr_11 = global::System.Linq.Expressions.Expression.Equal(expr_1, expr_9);
var expr_12 = global::System.Linq.Expressions.Expression.Condition(expr_11, expr_10, expr_7, typeof(string));
var expr_13 = global::System.Linq.Expressions.Expression.Constant(global::Foo.Trend.Increase, typeof(global::Foo.Trend));
var expr_14 = global::System.Linq.Expressions.Expression.Convert(expr_13, typeof(global::Foo.Trend?));
var expr_15 = global::System.Linq.Expressions.Expression.Call(expr_14, typeof(global::Foo.Trend?).GetMethod("ToString", global::System.Reflection.BindingFlags.Public | global::System.Reflection.BindingFlags.NonPublic | global::System.Reflection.BindingFlags.Instance, null, new global::System.Type[] { }, null), global::System.Array.Empty<global::System.Linq.Expressions.Expression>());
var expr_16 = global::System.Linq.Expressions.Expression.Equal(expr_1, expr_14);
var expr_17 = global::System.Linq.Expressions.Expression.Condition(expr_16, expr_15, expr_12, typeof(string));
var expr_18 = global::System.Linq.Expressions.Expression.Constant(null, typeof(global::Foo.Trend?));
var expr_19 = global::System.Linq.Expressions.Expression.Equal(expr_1, expr_18);
var expr_20 = global::System.Linq.Expressions.Expression.Condition(expr_19, expr_2, expr_17, typeof(string));
var expr_21 = global::System.Linq.Expressions.Expression.Field(null, typeof(string).GetField("Empty", global::System.Reflection.BindingFlags.Public | global::System.Reflection.BindingFlags.NonPublic | global::System.Reflection.BindingFlags.Static)); // string.Empty
var expr_0 = global::System.Linq.Expressions.Expression.Coalesce(expr_20, expr_21);
return global::System.Linq.Expressions.Expression.Lambda<global::System.Func<global::Foo.Entity, string>>(expr_0, p__this);
}
}
}
56 changes: 56 additions & 0 deletions tests/ExpressiveSharp.Generator.Tests/ExpressiveGenerator/EnumTests.cs
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Expand Up @@ -333,4 +333,60 @@ public record Entity

return Verifier.Verify(result.GeneratedTrees[0].ToString());
}

[TestMethod]
public Task ExpandToStringOnNullableEnum()
{
var compilation = CreateCompilation(
"""
namespace Foo {
public enum Trend { Increase, Decrease, NoChange }

public record Entity
{
public Trend? Trend { get; init; }

[Expressive]
public string TrendLabel => Trend.ToString() ?? string.Empty;
}
}
""");
var result = RunExpressiveGenerator(compilation);

Assert.AreEqual(0, result.Diagnostics.Length);
Assert.AreEqual(1, result.GeneratedTrees.Length);

return Verifier.Verify(result.GeneratedTrees[0].ToString());
}

[TestMethod]
public Task ExpandExtensionMethodOnNullableEnum()
{
var compilation = CreateCompilation(
"""
namespace Foo {
public enum Trend { Increase, Decrease, NoChange }

public static class TrendExtensions
{
public static string Describe(this Trend? value) =>
value.HasValue ? value.Value.ToString() : "n/a";
}

public record Entity
{
public Trend? Trend { get; init; }

[Expressive]
public string TrendLabel => Trend.Describe();
}
}
""");
var result = RunExpressiveGenerator(compilation);

Assert.AreEqual(0, result.Diagnostics.Length);
Assert.AreEqual(1, result.GeneratedTrees.Length);

return Verifier.Verify(result.GeneratedTrees[0].ToString());
}
Comment on lines +362 to +391
}
22 changes: 22 additions & 0 deletions tests/ExpressiveSharp.IntegrationTests/Tests/EnumComparisonTests.cs
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Expand Up @@ -70,6 +70,25 @@ public void ExpressivePropertyOnEnumComparison_RegistryResolves()

Assert.IsNotNull(registered);
}

[TestMethod]
public void ToStringOnNullableEnum_ExpandExpressives_MaterializesAndEvaluates()
{
var source = new List<EnumComparisonEntity>
{
new() { NullableValue = Bucket.Low },
new() { NullableValue = Bucket.Mid },
new() { NullableValue = Bucket.High },
new() { NullableValue = null },
}.AsQueryable();

Expression<Func<EnumComparisonEntity, string>> expr = e => e.NullableLabel;
var expanded = (Expression<Func<EnumComparisonEntity, string>>)expr.ExpandExpressives();

var labels = source.Select(expanded.Compile()).ToList();

CollectionAssert.AreEqual(new[] { "Low", "Mid", "High", "" }, labels);
}
}

public class EnumComparisonEntity
Expand All @@ -88,6 +107,9 @@ public class EnumComparisonEntity

[Expressive]
public bool IsLowOrMid => NullableValue <= Bucket.Mid;

[Expressive]
public string NullableLabel => NullableValue.ToString() ?? string.Empty;
}

public enum Bucket { Low, Mid, High }
Expand Down
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