principle-boundary-discipline

边界纪律

Place validation, type narrowing, and error handling at system boundaries. Trust internal code unconditionally. Business logic lives in pure functions. The shell is thin and mechanical.

把校验、类型收窄、错误处理放在系统边界。无条件信任内部代码。业务逻辑住在纯函数里。外壳又薄又机械。

Why: Scattered validation is noisy, redundant, and gives a false sense of safety. Keep logic out of framework wiring so it can be tested without the framework.

为什么： 散落的校验又吵又冗余，还制造虚假安全感。逻辑别塞进框架接线，这样不用框架也能测。

The pattern:

模式：

• At boundaries (CLI args, config files, external APIs, network protocols): validate, return errors, handle defensively.

• Inside the system: typed data, error propagation, no re-validation. Trust the types.

• Across the boundary. Expose domain concepts, not the boundary’s private representation. Keep general-purpose mechanism inside and special-purpose policy at the edge.

• 在边界（CLI 参数、配置文件、外部 API、网络协议）：校验、返回错误、防御性处理。

• 系统内部： 类型化数据、错误传播、不再校验。信任类型。

• 跨过边界。 暴露领域概念，不是边界的私有表示。通用机制放里面，特化策略放边缘。

Applications:

应用：

Validation and error handling:

校验与错误处理：

• Validate config at parse time (the boundary), not inside business logic

• Parse raw data into domain types at the boundary

• Do not re-export transport, storage, framework, or wire types through the public surface

• No redundant nil checks deep in call chains if the boundary already validated

• 在解析时（边界）校验配置，别在业务逻辑里

• 在边界把原始数据解析成领域类型

• 别通过公开面再导出传输、存储、框架或 wire 类型

• 边界已校验过，调用链深处别再塞冗余 nil 检查

Code organization:

代码组织：

• Business logic in pure functions with no framework dependencies

• Parse functions: pure transforms from raw bytes to typed state

• Prompt construction: structured state in, string out

• Scoring and assessment: pure transforms from state to results

• 业务逻辑放无框架依赖的纯函数

• 解析函数：原始字节到类型化状态的纯变换

• Prompt 构造：结构化状态进，字符串出

• 打分与评估：状态到结果的纯变换

The tests:

自检：

• “Is this data crossing a system boundary right now?” If not, validation is redundant.

• “Can this be a pure function that the shell just calls?” If yes, extract it.

• 「这份数据此刻正在跨系统边界吗？」不是，校验就多余。

• 「这能做成外壳只管调用的纯函数吗？」能，就抽出来。