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README.md

MetaObjects — C#

The C# port of the cross-language MetaObjects metadata standard. Targets .NET 8 (C# 12).

What it covers

  • Loader (MetaObjects) — multi-file JSON / YAML loader with overlay merge and cross-file extends: resolution.
  • Canonical serializer — byte-identical output to the TypeScript reference (the cross-language wire format).
  • YAML authoring front-end — sigil-free attrs + []-array suffix + fused-key default subtype + the D2 type-coercion guard (ADR-0006), via YamlDotNet. The cross-language interchange remains canonical JSON; YAML lowers to it.
  • Codegen (MetaObjects.Codegen) — idiomatic .NET emit: EF Core entities, an AppDbContext, ASP.NET minimal-API CRUD routes, filter allowlists, payload records, output parsers/prompts, TPH per-subtype surfaces and M:N navigation.
  • Render + verify (MetaObjects.Render) — Mustache render, payload value-object codegen and the verify drift gates, byte-identical with the other four ports against the shared render corpus.
  • CLI (MetaObjects.Cli) — packaged as a .NET tool invoked dotnet meta, with gen and verify verbs.
  • Conformance runners — auto-discover the shared corpora under fixtures/ (metamodel, yaml, render, verify, validation, api-contract, persistence, registry manifest). The corpora are the oracles — when a fixture goes red the port is wrong, never the fixture.

What it does NOT cover (out of scope)

  • Schema migrations. Per ADR-0015 the migration engine is owned by the TypeScript toolchain; the C# migrate engine and its migrate / --from-db CLI surface were removed. Use the Node meta CLI (meta migrate, meta verify --db) for schema. This is only about schema — C# codegen and runtime data access are first-class here.
  • Byte-equal generated code. Each language emits its own idiomatic output; byte equivalence is a goal at the render/canonical-serializer layer, not the codegen layer. Cross-port codegen parity is enforced behaviourally, through the api-contract corpus.
  • The dbProvider provider — the metamodel conformance corpus uses only metaobjects-core-types.

AI assistant context

To scaffold MetaObjects context files (.metaobjects/AGENTS.md, .metaobjects/CLAUDE.md, and .claude/skills/metaobjects-*/) into your project so your AI assistant understands how to author metadata and run codegen, use the Node meta CLI:

npx meta agent-docs --server csharp

(Running dotnet meta agent-docs prints this redirect and exits.)

Running

cd server/csharp
dotnet test

The test suite includes per-fixture Lint and Conformance theories over the shared corpus at ../fixtures/conformance/ plus unit tests for the parser, serializer, registry, tree, and loader.

Layout

  • MetaObjects/ — class library (MetaObjects.csproj)
    • Constants.cs, Errors.cs, Registry.cs, Provider.cs, DataType.cs, DataConverter.cs
    • Meta/MetaData.cs and the concrete node classes (MetaRoot, MetaObject, MetaField, etc.)
    • CoreAttrSchemas.cs, CoreTypes.cs — the metaobjects-core-types provider
    • Parser.cs, SuperResolve.cs, SerializerJson.cs
    • YamlDesugar.cs, ParserYaml.cs — YAML authoring front-end (ADR-0006)
    • Loader/ — IMetaDataSource, InMemoryStringSource, FileSource, DirectorySource, UriSource, MetaDataLoader (with FromDirectory/FromUris/FromString static factories), ValidationPasses
  • MetaObjects.Conformance.Tests/ — xUnit test project + conformance harness
    • ConformanceAdapter.cs, FixtureDiscovery.cs, OperationScript.cs, FixtureLint.cs, Navigator.cs, CapabilityBinding.cs, Result.cs, ExpectedFailures.cs, conformance-expected-failures.json, ConformanceTests.cs
    • YamlConformanceTests.cs, YamlDesugarTests.cs, yaml-conformance-expected-failures.json — YAML conformance + unit tests
    • Per-pipeline-stage unit tests (ErrorsTests, RegistryTests, TreeTests, ParserTests, SerializerTests, LoaderTests, SuperResolveTests, ValidationTests, …)
  • MetaObjects.Codegen/ — the .NET emit pipeline (Generators/ holds entity, db-context, routes, payload, filter-allowlist, output-parser/prompt, extractor, template) + CodegenRunner, GeneratorRegistry, CodegenDrift
  • MetaObjects.Render/ — Mustache render, payload value objects, verify
  • MetaObjects.Cli/ — the dotnet meta tool (gen, verify)
  • MetaObjects.Codegen.Tests/, MetaObjects.Render.Tests/, MetaObjects.Cli.Tests/ — per-project unit + golden tests
  • MetaObjects.IntegrationTests/ — the generated ASP.NET stack booted over HTTP against Testcontainers Postgres (api-contract + persistence corpora)