Multi-select custom answer composition
多选题自定义答案组合
The user-questions result vocabulary carries selected option labels and optional custom text in separate fields, but its original semantics made them mutually exclusive for every question. On a multi-select question, opening or typing the custom answer discarded labels the user had already selected. The TUI returned only the custom text, and the Web host rejected a client response that preserved both fields.
English
Problem
The user-questions result vocabulary carries selected option labels and optional custom text in separate fields, but its original semantics made them mutually exclusive for every question. On a multi-select question, opening or typing the custom answer discarded labels the user had already selected. The TUI returned only the custom text, and the Web host rejected a client response that preserved both fields.
Decision
For a question with multiSelect: true, one answer item may contain both a non-empty selected array and non-empty custom text. Web drafts preserve both values regardless of whether the user selects an option or types custom text first; the TUI retains pending custom text across option/custom mode switches and projects it with checked labels from either submit mode; and the Web host accepts the combined response after applying its existing id, label, uniqueness, batch, and non-empty-text validation.
Single-select and optionless questions keep exclusive semantics: custom text overrides any selected option. The result shape remains { id, selected, custom? }, so no wire or tool-output schema changes.
Alternatives considered
Encode custom text as another selected label. Rejected because it would erase the distinction between caller-provided option labels and human-authored text, weakening validation and forcing consumers to infer which value was custom.
Allow selected and custom together for every question. Rejected because a single-select question represents one answer; permitting a selected option plus custom text would make its cardinality ambiguous. The combined form is limited to questions that explicitly opt into multiple answers.
Consequences
Multi-select UIs can represent the user's complete answer without discarding either source. Providers and consumers retain the existing DTO, while request-aware validators interpret the allowed combination from multiSelect. Web component and assembled-browser coverage, TUI coverage, host-response coverage, and tool-projection coverage pin the combined result. Web, TUI, and tool-projection coverage also retain labels-only answers; assembled keyless TUI coverage pins the combined terminal flow, and single-select host coverage pins the remaining exclusivity rule.
中文
问题
用户交互结果的词汇分别通过不同字段携带选中的选项标签和可选的自定义文本，但最初的语义要求每个问题的这两个字段互斥。对于多选题，打开自定义答案或输入文本会丢弃用户已选中的标签。TUI 只返回自定义文本，而 Web 宿主会拒绝同时保留两个字段的客户端响应。
决策
对于 multiSelect: true 的问题，一个回答项可以同时包含非空 selected 数组与非空 custom 文本。无论用户先选择选项还是先输入自定义文本，Web 草稿都会保留两个值；TUI 在选项与自定义模式之间切换时会保留待提交的自定义文本，并在任一模式提交时将其与已勾选的标签一同投影；Web 宿主则在应用现有的 id、标签、唯一性、批次和非空文本校验后接受组合响应。
单选题和无选项问题仍保持互斥语义：自定义文本会覆盖任何已选中的选项。结果形状仍为 { id, selected, custom? }，因此协议或工具输出 schema 均无需变更。
考虑过的替代方案
把自定义文本编码为另一个 selected 标签。 不予采纳，因为这样会抹去调用方提供的选项标签与用户填写文本之间的区别，削弱校验，并迫使消费方推断哪个值属于自定义内容。
允许所有问题同时使用 selected 与 custom。 不予采纳，因为单选题只表示一个回答；允许选中选项与自定义文本并存会使其基数含义模糊。组合形式仅适用于显式启用多回答的问题。
后果
多选 UI 可以完整表达用户的回答，不会丢弃任一来源。提供方和消费方继续使用现有 DTO，而请求感知的校验器会根据 multiSelect 判断是否允许组合。Web 组件与组装浏览器的测试覆盖、TUI 测试覆盖、宿主响应测试覆盖和工具投影测试覆盖共同固定组合结果。Web、TUI 与工具投影测试覆盖还固定了仅含标签的回答形态；组装后的无密钥 TUI 测试覆盖固定终端中的组合回答流程，单选题的宿主测试覆盖则固定其余的互斥规则。