29 lines
1.3 KiB
Markdown
29 lines
1.3 KiB
Markdown
# dsh-brand
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English | [中文](README.zh.md)
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The `Branded<B>` nominal-typing primitive — a tiny, **type-only** package (no runtime code, no harness-package dependency) shared by every package that owns a cross-boundary id.
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## What `Branded` is
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A brand makes structurally-identical strings non-interchangeable at the type level: a `SessionId` cannot be passed where a `CallId` is expected, even though both are plain `string`s at runtime.
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```ts
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import type { Branded } from '@deepseek-ai/dsh-brand'
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export type SessionId = Branded<'SessionId'>
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/** Brand a string as a SessionId (a plain cast — zero runtime cost). */
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export function SessionId(id: string): SessionId {
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return id as SessionId
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}
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```
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Construction goes through the per-id factory in the owning package. Comparison, logging, JSON serialization, and the wire format behave as for an ordinary string; the brand is erased at compile time.
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## Policy: brand ids that cross package boundaries
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A package brands the ids it owns — `CallId` in `dsh-llm`, the shared agent/session `SessionId` in `dsh-session`, and `TaskId` in `dsh-tasks`. Brand cross-package ids that could plausibly be confused; not every string needs one.
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This package owns only the primitive. Keeping it dependency-free lets `dsh-tasks`, for example, brand `TaskId` without importing an unrelated capability package merely to reach `Branded`.
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