62 lines
2.9 KiB
Markdown
62 lines
2.9 KiB
Markdown
# Yak 02 — C# solution: the AFTER situation (plain domain + DTOs + mappers)
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## Context
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Depends on Yak 01 (solution, `Before/` project, test project already exist).
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Implement the "after" half of the exercise in the existing `After/` project
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and add tests. See `after-dto.mmd` for the diagram:
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- `Client`, `Order` — **plain** domain objects, no `DbBase` inheritance,
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no knowledge of `DbContext`
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- `ClientDto`, `OrderDto` — DTOs carrying the same data **including the
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relations** (`ClientDto.Orders`, back-references)
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- `Mappers` — hand-written mapping, each way:
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`ToClientDto`, `FromClientDto`, `ToOrderDto`, `FromOrderDto`
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- `DbContext`/`DbBase` — still exist (persistence layer), but the domain no
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longer subclasses/leaks them
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- `WebApp` — consumes **only DTOs**
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## Rules
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- Do NOT modify `Before/` (it's the frozen "before" state).
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- Hand-write the mappers (no AutoMapper) — the mapping code is part of the
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illustration. Mappers must not mutate their inputs.
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- Keep the fake `DbContext`/`DbBase` for persistence in `After/` (or reuse the
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idea from `Before/`), but the domain types must not derive from `DbBase`.
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Persisting a domain object now requires explicit registration (e.g. a
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`DbContext.Save(client)` that copies into a tracked entity, or registers an
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adapter) — the direction of dependency is flipped.
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## Required tests (AfterTests)
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At minimum, mirroring the Before tests where meaningful:
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1. `Client`/`Order` do **not** derive from `DbBase`, and (via reflection)
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expose no `DbContext`-typed property or field — the leak is gone.
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2. Mappers map all scalar fields, in both directions
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(`Client → ClientDto`, `ClientDto → Client`, same for `Order`).
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3. Mappers map the relations: `Client.Orders` → `ClientDto.Orders`, and the
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`Order.Client` / `OrderDto.ClientDto` back-references stay consistent.
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4. Round-trip: `FromX(ToX(domain))` equals the original domain state
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(compare by values, not reference); same for DTO round-trip.
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5. Mappers do not mutate their input (snapshot fields, map, compare).
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6. `WebApp` (after version) methods consume only `ClientDto`/`OrderDto`;
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assert the `After.WebApp` type references no domain or DbContext type in
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its public API (reflection over member signatures).
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7. Persistence still works through the fake `DbContext` in the after world.
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## Acceptance criteria
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- `dotnet build` and `dotnet test` succeed on the full solution
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(Before + After + tests), 0 warnings.
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- No NuGet packages beyond xUnit's default set.
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- `Before/` project unmodified (diff check).
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- Committed with a message referencing this yak.
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## Open questions (answer before starting, defaults in parens)
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1. How should the after-world persistence flip look — explicit
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`ctx.Save(domainObject)` with internal entity/DTO translation, or something
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else? (explicit Save with translation, minimal)
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2. Are DTOs records (value equality helps round-trip tests) or plain classes?
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(records) |