Support multiple JsonSerializerContext classes for polymorphic types

AGENTS.md

@@ -0,0 +1,172 @@
+# Agent Guidelines for JSON Converter Source Generator
+
+This repository contains a C# source generator for JSON converters supporting polymorphic contracts and enum serialization.
+
+## Build & Test Commands
+
+### Basic Commands
+```bash
+# Restore dependencies
+dotnet restore --nologo
+
+# Build entire solution (Release)
+dotnet build --no-restore --nologo --configuration Release
+
+# Build specific project
+dotnet build src/Aviationexam.GeneratedJsonConverters.SourceGenerator/Aviationexam.GeneratedJsonConverters.SourceGenerator.csproj --configuration Release
+
+# Run all tests
+dotnet test --no-build --configuration Release --results-directory TestResults --report-trx
+
+# Run specific test project
+dotnet test src/Aviationexam.GeneratedJsonConverters.SourceGenerator.Tests/Aviationexam.GeneratedJsonConverters.SourceGenerator.Tests.csproj --configuration Release
+
+# Run single test by fully qualified name
+dotnet test --filter "FullyQualifiedName~EnumJsonConverterIncrementalGeneratorSnapshotTests.SimpleWorks" --configuration Release
+
+# Run all tests in a class
+dotnet test --filter "FullyQualifiedName~EnumJsonConverterIncrementalGeneratorSnapshotTests" --configuration Release
+```
+
+### Code Style & Linting
+```bash
+# Check code formatting (CI validation)
+dotnet format --no-restore --verify-no-changes -v diag
+
+# Apply code formatting
+dotnet format --no-restore
+```
+
+## Project Structure
+
+- **SourceGenerator**: Core source generator implementation (`netstandard2.0`)
+- **SourceGenerator.Tests**: Snapshot tests for generator output (xUnit v3, Microsoft Testing Platform)
+- **SourceGenerator.Target**: Sample target project demonstrating usage
+- **SourceGenerator.Target.Tests**: Integration tests for generated code
+
+## Code Style Guidelines
+
+### File & Namespace Conventions
+- **Line endings**: CRLF (enforced by `.editorconfig`)
+- **Encoding**: UTF-8 with BOM for `.cs` files
+- **Namespaces**: File-scoped namespaces (C# 14.0 / .NET 10)
+- **Namespace structure**: Should match folder structure (`dotnet_style_namespace_match_folder = true`)
+
+### C# Formatting
+```csharp
+// Indentation: 4 spaces for .cs files
+// Max line length: 160 characters
+// Space after cast: true
+// System directives: NOT sorted first (dotnet_sort_system_directives_first = false)
+
+// Example formatting:
+namespace Aviationexam.GeneratedJsonConverters.SourceGenerator;
+
+[Generator]
+public class EnumJsonConverterIncrementalGenerator : IIncrementalGenerator
+{
+    public const string Id = "AVI_EJC";
+
+    private const EnumSerializationStrategy DefaultEnumSerializationStrategy = 
+        EnumSerializationStrategy.FirstEnumName;
+}
+```
+
+### XML/Project Files
+- **Indentation**: 2 spaces for `.csproj`, `.targets`, `.props`
+- **Max line length**: 120 characters
+
+### Import Organization
+```csharp
+// Standard ordering (System namespaces NOT first)
+using Aviationexam.GeneratedJsonConverters.SourceGenerator.Extensions;
+using H.Generators.Extensions;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+```
+
+### Naming Conventions
+- **Enums**: Prefix with `E` (e.g., `EMyEnum`, `EBackingEnum`)
+- **Interfaces**: Prefix with `I` (e.g., `IDiscriminatorStruct`)
+- **Constants**: PascalCase with clear descriptors (e.g., `DefaultEnumSerializationStrategy`)
+- **Private fields**: Use `_camelCase` for instance fields (not shown in samples but standard C# practice)
+- **Method parameters**: camelCase
+- **Local variables**: camelCase
+
+### Type Usage
+- **Nullable reference types**: ENABLED (`<Nullable>enable</Nullable>`)
+- **LangVersion**: 14.0 (C# 14)
+- **Target frameworks**: `netstandard2.0` (generator), `net8.0;net9.0;net10.0` (tests)
+- Use modern C# features: file-scoped namespaces, target-typed `new()`, collection expressions `[..]`
+- Prefer `ImmutableArray` for generator collections
+- Use `SymbolEqualityComparer` for Roslyn symbol comparisons
+
+### Comments & Documentation
+- XML documentation not required for internal generator code (`GenerateDocumentationFile = false`)
+- Use clear, descriptive names over excessive comments
+- Comment complex logic (e.g., configuration parsing, symbol transformations)
+
+### Error Handling
+- Use nullable patterns and null-coalescing operators
+- Throw `ArgumentNullException` for critical null cases in generators
+- Use `out` parameters for converter names and diagnostic results
+- Leverage `ResultWithDiagnostics<T>` pattern for incremental generators
+
+### Testing Conventions
+- **Test framework**: xUnit v3 with Microsoft Testing Platform
+- **Snapshot testing**: Use `Verify` library for generator output validation
+- **Test naming**: `MethodName_Scenario` or `ScenarioWorks` pattern
+- **Theory data**: Use `[InlineData]` for parameterized tests
+- Disable specific warnings with `#pragma warning disable/restore` when intentional (e.g., `xUnit1025` for duplicate test values)
+
+### Generator-Specific Patterns
+```csharp
+// Use IncrementalValueProvider patterns
+context.SyntaxProvider.CreateSyntaxProvider(
+    predicate: static (node, _) => node is EnumDeclarationSyntax,
+    transform: TransformerMethod
+)
+.Collect()
+.Combine(otherProvider)
+.SelectAndReportExceptions(GetSourceCode, context, Id)
+.SelectAndReportDiagnostics(context)
+.AddSource(context);
+
+// Embed resources for generated attributes
+i.AddEmbeddedResources<GeneratorClass>([
+    "AttributeName",
+    "OtherTypeName",
+]);
+```
+
+### Build Configuration
+- **MSBuild properties prefix**: `AVI_EJC_` for this generator
+- **Configuration access**: Via `AnalyzerConfigOptionsProvider.GetGlobalOption()`
+- Example: `build_property.AVI_EJC_DefaultJsonSerializerContext_Namespace`
+
+## Common Pitfalls
+1. **Roslyn symbol comparisons**: Always use `SymbolEqualityComparer.Default.Equals()`, never `==`
+2. **Incremental generators**: Ensure all data structures implement proper equality for caching
+3. **Embedded resources**: Must be registered in `.csproj` and loaded in `PostInitialization`
+4. **netstandard2.0 constraints**: Be mindful of API availability in generator projects
+5. **Line endings**: Always CRLF (use `.editorconfig` settings)
+
+## Critical Diagnostic Rules (Error Severity)
+- CA1507: Use nameof when possible
+- CA2000, CA2012, CA2016: Dispose/async patterns
+- CA2213, CA2215, CA2217, CA2234: Dispose and base calls
+- CA53xx, CA59xx: Security-related analyzers
+
+## Testing Strategy
+- **Snapshot tests**: Verify generated source code exactly matches approved snapshots
+- **Integration tests**: Validate serialization/deserialization with actual JSON
+- **Configuration tests**: Test various MSBuild property combinations
+- Run tests with `--configuration Release` in CI to match production build
+
+## Version Control
+- Use GitVersion for semantic versioning
+- All changes must pass `dotnet format` validation
+- Tests must pass on .NET 8, 9, and 10

JsonConverter.SourceGenerator.sln.DotSettings

@@ -1,4 +1,5 @@
 <wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
+	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EUnitTestFramework_002EMigrations_002EEnableDisabledProvidersMigration/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/Environment/UnitTesting/DisabledProviders/=Testing_0020Platform/@EntryIndexedValue">False</s:Boolean>
 	<s:Boolean x:Key="/Default/Environment/UnitTesting/DisabledProviders/=VsTest/@EntryIndexedValue">True</s:Boolean>
-	<s:Boolean x:Key="/Default/UserDictionary/Words/=Aviationexam/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=Aviationexam/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>

src/Aviationexam.GeneratedJsonConverters.SourceGenerator.Target.Tests/Aviationexam.GeneratedJsonConverters.SourceGenerator.Target.Tests.csproj

@@ -23,8 +23,11 @@
     <PackageReference Include="System.Collections.Immutable" Version="10.0.1" />
     <PackageReference Include="System.Text.Encodings.Web" Version="10.0.1" />
     <PackageReference Include="System.IO.Pipelines" Version="10.0.1" />
-    <PackageReference Include="xunit.v3.mtp-v2" Version="3.2.1" />
     <PackageReference Include="System.Text.Json" Version="10.0.1" />
+    <PackageReference Include="Verify.XunitV3" Version="31.9.3" />
+    <PackageReference Include="Verify.SourceGenerators" Version="2.5.0" />
+    <PackageReference Include="xunit.v3.mtp-v2" Version="3.2.1" />
+    <PackageReference Include="ZLinq" Version="1.5.4" />
   </ItemGroup>
 
   <ItemGroup>

src/Aviationexam.GeneratedJsonConverters.SourceGenerator.Target.Tests/BaseContractWithCustomDelimiterSerializationTests.MyJsonSerializerContext.cs

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+using Aviationexam.GeneratedJsonConverters.SourceGenerator.Target.ContractWithCustomDelimiter;
+using System;
+using System.Text.Json;
+using System.Threading.Tasks;
+using VerifyTests;
+using VerifyXunit;
+using Xunit;
+
+namespace Aviationexam.GeneratedJsonConverters.SourceGenerator.Target.Tests;
+
+public partial class BaseContractWithCustomDelimiterSerializationTests
+{
+    [Theory]
+    [MemberData(nameof(BaseJsonContractData))]
+    public void DeserializeBaseContractWorks(string json, Type targetType)
+    {
+        var baseContract = JsonSerializer.Deserialize<BaseContractWithCustomDelimiter>(
+            json,
+            MyJsonSerializerContext.Default.Options
+        );
+
+        Assert.NotNull(baseContract);
+        Assert.Equal(1, baseContract.BaseProperty);
+        Assert.IsType(targetType, baseContract);
+
+        if (baseContract is LeafContractWithCustomDelimiter leafContract)
+        {
+            Assert.Equal(2, leafContract.LeafProperty);
+        }
+    }
+
+    [Theory]
+    [MemberData(nameof(LeafContractData))]
+    public Task SerializeBaseContractWorks(int testId, BaseContractWithCustomDelimiter contract)
+    {
+        var json = JsonSerializer.Serialize(
+            contract,
+            MyJsonSerializerContext.Default.Options
+        );
+
+        var settings = new VerifySettings();
+        settings.UseParameters(testId);
+
+        return Verifier.VerifyJson(json, settings);
+    }
+}

src/Aviationexam.GeneratedJsonConverters.SourceGenerator.Target.Tests/BaseContractWithCustomDelimiterSerializationTests.MySecondJsonSerializerContext.cs

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+using Aviationexam.GeneratedJsonConverters.SourceGenerator.Target.ContractWithCustomDelimiter;
+using System;
+using System.Text.Json;
+using System.Threading.Tasks;
+using VerifyTests;
+using VerifyXunit;
+using Xunit;
+
+namespace Aviationexam.GeneratedJsonConverters.SourceGenerator.Target.Tests;
+
+public partial class BaseContractWithCustomDelimiterSerializationTests
+{
+    [Theory]
+    [MemberData(nameof(BaseJsonContractData))]
+    public void DeserializeBaseContractWorks_withMySecondJsonSerializerContext(string json, Type targetType)
+    {
+        var baseContract = JsonSerializer.Deserialize<BaseContractWithCustomDelimiter>(
+            json,
+            MySecondJsonSerializerContext.Default.Options
+        );
+
+        Assert.NotNull(baseContract);
+        Assert.Equal(1, baseContract.BaseProperty);
+        Assert.IsType(targetType, baseContract);
+
+        if (baseContract is LeafContractWithCustomDelimiter leafContract)
+        {
+            Assert.Equal(2, leafContract.LeafProperty);
+        }
+    }
+
+    [Theory]
+    [MemberData(nameof(LeafContractData))]
+    public Task SerializeBaseContractWorks_withMySecondJsonSerializerContext(int testId, BaseContractWithCustomDelimiter contract)
+    {
+        var json = JsonSerializer.Serialize(
+            contract,
+            MySecondJsonSerializerContext.Default.Options
+        );
+
+        var settings = new VerifySettings();
+        settings.UseParameters(testId);
+
+        return Verifier.VerifyJson(json, settings);
+    }
+}

src/Aviationexam.GeneratedJsonConverters.SourceGenerator.Target.Tests/BaseContractWithCustomDelimiterSerializationTests.SerializeBaseContractWorks_testId=1.verified.txt

@@ -0,0 +1,5 @@
+{
+  myCustomDelimiter: LeafContractWithCustomDelimiter,
+  leafProperty: 2,
+  baseProperty: 1
+}

src/Aviationexam.GeneratedJsonConverters.SourceGenerator.Target.Tests/BaseContractWithCustomDelimiterSerializationTests.SerializeBaseContractWorks_testId=2.verified.txt

@@ -0,0 +1,5 @@
+{
+  myCustomDelimiter: NullableLeafContractWithCustomDelimiter,
+  leafProperty: 2,
+  baseProperty: 1
+}

src/Aviationexam.GeneratedJsonConverters.SourceGenerator.Target.Tests/BaseContractWithCustomDelimiterSerializationTests.SerializeBaseContractWorks_testId=3.verified.txt

@@ -0,0 +1,5 @@
+{
+  myCustomDelimiter: NullableLeafContractWithCustomDelimiter,
+  leafProperty: null,
+  baseProperty: 1
+}

src/Aviationexam.GeneratedJsonConverters.SourceGenerator.Target.Tests/BaseContractWithCustomDelimiterSerializationTests.SerializeBaseContractWorks_withMySecondJsonSerializerContext_testId=1.verified.txt

@@ -0,0 +1,5 @@
+{
+  myCustomDelimiter: LeafContractWithCustomDelimiter,
+  leafProperty: 2,
+  baseProperty: 1
+}

src/Aviationexam.GeneratedJsonConverters.SourceGenerator.Target.Tests/BaseContractWithCustomDelimiterSerializationTests.SerializeBaseContractWorks_withMySecondJsonSerializerContext_testId=2.verified.txt

@@ -0,0 +1,5 @@
+{
+  myCustomDelimiter: NullableLeafContractWithCustomDelimiter,
+  leafProperty: 2,
+  baseProperty: 1
+}

src/Aviationexam.GeneratedJsonConverters.SourceGenerator.Target.Tests/BaseContractWithCustomDelimiterSerializationTests.SerializeBaseContractWorks_withMySecondJsonSerializerContext_testId=3.verified.txt

@@ -0,0 +1,4 @@
+{
+  myCustomDelimiter: NullableLeafContractWithCustomDelimiter,
+  baseProperty: 1
+}