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Suppress union ambiguity warning when a global classified is specified at compile time #131797

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Merged
eiriktsarpalis merged 3 commits into from
Aug 5, 2026
+3 −9
Merged

Suppress union ambiguity warning when a global classified is specified at compile time #131797

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acccc0d
Suppress union warning for global classifiers
eiriktsarpalis Aug 4, 2026
51e32b5
Address union classifier review feedback
eiriktsarpalis Aug 4, 2026
abb7e38
Apply suggestion from @eiriktsarpalis
eiriktsarpalis Aug 4, 2026
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2 changes: 1 addition & 1 deletion src/libraries/System.Text.Json/gen/JsonSourceGenerator.Parser.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -988,7 +988,7 @@ private void ProcessTypeCustomAttributes(
List<DerivedTypeSpec>? derivedTypes = null;
HashSet<object>? typeDiscriminators = null;
bool hasExplicitDerivedTypeAttribute = false;
bool hasUnionTypeClassifierSpecified = false;
bool hasUnionTypeClassifierSpecified = options?.TypeClassifiers is { Count: > 0 };
bool isUnionType = IsUnionType(typeToGenerate.Type);
INamedTypeSymbol? namedUnionType = typeToGenerate.Type as INamedTypeSymbol;

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10 changes: 2 additions & 8 deletions ...tests/System.Text.Json.SourceGeneration.Unit.Tests/JsonSourceGeneratorDiagnosticsTests.cs
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Expand Up @@ -781,7 +781,7 @@ public override JsonTypeClassifier CreateJsonClassifier(JsonTypeClassifierContex
}

[Fact]
public void UnionWithAmbiguousCaseTypesAndOptionsClassifier_CompilesWithWarning()
public void UnionWithAmbiguousCaseTypesAndOptionsClassifier_CompilesWithoutWarning()
{
string source = """
using System;
Expand Down Expand Up @@ -815,14 +815,8 @@ public override JsonTypeClassifier CreateJsonClassifier(JsonTypeClassifierContex

Compilation compilation = CompilationHelper.CreateCompilation(source);
JsonSourceGeneratorResult result = CompilationHelper.RunJsonSourceGenerator(compilation, disableDiagnosticValidation: true);
Location unionLocation = compilation.GetSymbolsWithName("IntOrLongUnion").First().Locations[0];

var expectedDiagnostics = new DiagnosticData[]
{
new(DiagnosticSeverity.Warning, unionLocation, "Union type 'IntOrLongUnion': case types 'int', 'long' all serialize as JSON value type 'Number'. Set JsonUnionAttribute.TypeClassifier to provide a custom classifier that can disambiguate."),
};

CompilationHelper.AssertEqualDiagnosticMessages(expectedDiagnostics, result.Diagnostics);
Assert.Empty(result.Diagnostics);
}

[Fact]
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