Module questionnaire 

Questionnaire answer sheets: render a prose questionnaire, collect answers interactively or from a document, and decode them by stable identity through one shared validation pipeline. Structs that derive Questionnaire lower to this same runtime model and fill themselves from validated Answers without a serde boundary.

standout-input owns the reusable machinery: definition validation, deterministic rendering, parsing, collection adapters, shared field decoding and validation, derive-support traits, and diagnostics. The application owns its questionnaire definition, whole-form rules (a closure passed to Questionnaire::decode_answers_with), interactive flow, review, confirmation, and side effects.

Rendered format

A rendered sheet is a preamble (format version, questionnaire ID, fingerprint) followed by numbered questions, each ending in a stable <id:...> tag. A line is a question line iff it ends with a tag as its last non-whitespace content — any trailing content, even a period, demotes it to prose. The answer is everything between a question line and the next one (or EOF); everything before the tag (numbering, wording, indentation, hint) is cosmetic and may be freely reworded. Declared defaults render pre-filled. One limitation is accepted by design: an answer that itself ends in a schema-valid tag reads as a question line — there is no escaping, only a warning-level diagnostic (RawAnswers::warnings) when answer text contains a stray <id:.

Nested and repeatable groups

Alongside scalar fields, a questionnaire may declare Groups: nested sections answered once, or repeatable sections answered once per submitted item within Repeat bounds. Adding an item to a repeatable group is copy-the-block editing — duplicate one rendered block below the last and answer the copy; a group occurrence is counted as a line ending with the group’s tag, never by numbering or prose. Definition IDs never change (every input’s name field is command.inputs.name); a submitted instance is addressed by its occurrence path, which inserts a zero-based index per enclosing repeatable-group occurrence (command.inputs[1].name). Answers and RawAnswers are keyed by occurrence path and expose occurrence_count; indexes belong to an answer instance, not the definition, so they never enter the fingerprint.

Decoding

One blank rule applies everywhere: a blank answer resolves to the declared default first; without one, a blank optional field is an omission and a blank required field is a missing-value error. A conditional field (ScalarField::active_when) is asked and enforced only while its controller holds the expected value; a populated inactive field is an error rather than silently discarded. A default may instead be dynamic (ScalarField::with_dynamic_default): a closure over earlier decoded answers, paired with a mandatory revision that enters the fingerprint in the static default’s place (closures can’t be hashed). Interactive collection re-prompts only on a failed entered answer, keeping earlier answers; batch collection (file/stdin) accumulates every diagnostic from one pass instead.

Compatibility

The preamble pins a format version, questionnaire ID, and a semantic fingerprint; parsing requires an exact match on all three; a stale sheet gets a diagnostic asking for a fresh one rather than a guessed mapping. The fingerprint covers every property that changes accepted answers — IDs, kinds, optionality, defaults, constraints, conditions, and validator/dynamic-default revisions — and ignores wording, numbering, and ordering. It is a compatibility checksum only, not an authentication or tamper-detection mechanism.

Sensitive content

Answer sheets are plain text and may hold private or sensitive values: keep saved sheets out of version control and delete them when done. Diagnostics identify fields by ID and line number without echoing answer values; application validators and form messages should do the same.

Structs

Answers

Condition

DynamicDefault

EarlierAnswers

FieldValidator

FormError

Group

Questionnaire

QuestionnaireChoiceParseError

RawAnswers

Repeat

ScalarField

Enums

AnswerSheetDiagnostic

AnswerValue

Constraint

Item

QuestionnaireError

QuestionnaireInputError

ScalarKind

ValidationDiagnostic

Traits

QuestionnaireChoices

QuestionnaireInput