449 lines
14 KiB
Rust
449 lines
14 KiB
Rust
//! Rendering a printed exam with Typst.
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//!
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//! Typst rather than LaTeX because the toolchain is one binary with no package
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//! manager, the error messages point at a line, and the compile is fast enough to
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//! iterate on. `pixi run -e docs typst compile` turns the output of this module
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//! into a PDF.
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//!
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//! ## What changed, and why
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//!
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//! This module used to build a document with `format!`. That made the position of
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//! the points label a Rust change, put a `#grid` call in a match arm, and meant
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//! the only way to move something on the page was to fork the crate. It also made
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//! a generated exam a dead end: you could edit the output, but the next export
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//! overwrote the edit.
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//!
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//! So the tool no longer writes documents. It loads a Typst file that you own,
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//! finds the markers in it, and injects data:
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//!
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//! ```typst
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//! // coursebank:begin questions
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//! #render-question((number: 1, stem: [Sample.], options: ()))
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//! // coursebank:end questions
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//! ```
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//!
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//! `render-question` is defined in your template. What the payload contains is
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//! governed by [`config::RenderConfig`]; where it lands and how it looks is
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//! governed by the template. The default templates are compiled into the binary,
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//! and `coursebank template dump` writes them into `templates/` so that
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//! customizing means editing a file. See [`template`] for the marker syntax, the
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//! slot list, and the lookup order.
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//!
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//! ## What is still enforced here
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//!
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//! Two invariants survived the rewrite, because both are the kind of mistake a
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//! room full of students discovers simultaneously.
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//!
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//! **A form's key is derived from the same permutation as its paper.** Option order
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//! comes from [`select::option_order`](crate::select::option_order) against the
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//! form's recorded seed, never from anything stored, so every export of form B
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//! agrees with every other. The paper, the key, and the answer sheet are all built
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//! from one [`payload::Payload`].
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//!
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//! **The paper's payload does not contain the answer.** Not `correct: false`, not a
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//! flag to check — the field is absent. See [`config::Reveal`]. A template cannot
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//! leak what it was never given, and that stays true through every future edit of
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//! the template by someone who has not read this comment.
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pub mod config;
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pub mod payload;
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pub mod template;
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pub mod value;
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use std::path::{Path, PathBuf};
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pub use config::{
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ConfigFile, ContentMode, Fields, LetterStyle, Overrides, RenderConfig, Reveal, StimulusMode,
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Variant, CONFIG_FILE, CONFIG_TEMPLATE,
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};
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pub use payload::Payload;
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pub use template::{Origin, Slot, Template};
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pub use value::Value;
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use crate::assessment::{AssessmentFile, Form};
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use crate::catalog::Catalog;
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use crate::course::Layout;
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use crate::error::{Error, Result};
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/// What to render.
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#[derive(Debug, Clone)]
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pub struct Options {
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/// Which form.
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pub form: Form,
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/// Which document.
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pub variant: Variant,
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/// A template path that overrides the usual lookup. Takes precedence over
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/// `template` in the render config.
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pub template: Option<PathBuf>,
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/// What to put in the payload, and how.
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pub config: RenderConfig,
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}
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impl Default for Options {
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fn default() -> Options {
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Options {
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form: Form {
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id: "A".to_string(),
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seed: 0,
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shuffle_items: false,
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shuffle_options: false,
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},
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variant: Variant::Exam,
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template: None,
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config: RenderConfig::for_variant(Variant::Exam),
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}
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}
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}
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impl Options {
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/// Options for one variant, with that variant's default configuration.
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///
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/// # Arguments
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///
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/// * `variant` - which document.
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/// * `form` - the form to render.
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///
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/// # Returns
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///
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/// The options.
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pub fn new(variant: Variant, form: Form) -> Options {
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Options {
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form,
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variant,
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template: None,
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config: RenderConfig::for_variant(variant),
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}
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}
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/// The template path to use, preferring the explicit one.
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fn template_path(&self) -> Option<&Path> {
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self.template.as_deref().or(self.config.template.as_deref())
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}
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}
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/// A finished document, with everything a caller needs to explain it.
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#[derive(Debug, Clone)]
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pub struct Rendered {
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/// Which document this is.
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pub variant: Variant,
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/// Where the template came from.
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pub origin: Origin,
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/// Which slots the template declared and this render filled.
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pub slots: Vec<Slot>,
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/// The Typst source.
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pub text: String,
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/// The payload, kept so a caller can also write it as JSON without rebuilding.
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pub payload: Payload,
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/// Advisory problems: markup that will probably confuse the Typst compiler, and
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/// a template that declared no markers at all.
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pub warnings: Vec<String>,
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}
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/// Renders one document.
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///
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/// # Arguments
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///
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/// * `catalog` - the loaded course.
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/// * `record` - the assessment record.
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/// * `opts` - what to render.
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///
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/// # Returns
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///
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/// The finished document.
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///
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/// # Errors
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///
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/// Returns [`Error::Unresolved`] when a placement references a missing item,
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/// [`Error::Io`] when an explicitly requested template cannot be read, and
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/// [`Error::Invalid`] when the template's markers are malformed or every placement
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/// is marked dropped.
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pub fn render(catalog: &Catalog, record: &AssessmentFile, opts: &Options) -> Result<Rendered> {
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let template = template::load(
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&catalog.layout,
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opts.variant,
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Some(record.assessment.id.as_str()),
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opts.template_path(),
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)?;
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let payload = payload::build(catalog, record, &opts.form, &opts.config)?;
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if payload.questions.is_empty() {
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return Err(Error::Invalid(vec![
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"this assessment has no printable items; every placement is marked dropped".to_string(),
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]));
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}
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// Only build what the template asked for. A paper template that never mentions
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// `data` should not pay for a second copy of every stem.
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let mut bodies = Vec::new();
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if template.wants(Slot::Meta) {
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bodies.push((Slot::Meta, payload::meta_body(&payload, &opts.config)));
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}
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if template.wants(Slot::Questions) {
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bodies.push((
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Slot::Questions,
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payload::questions_body(&payload, &opts.config),
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));
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}
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if template.wants(Slot::Data) {
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bodies.push((Slot::Data, payload::data_body(&payload, &opts.config)));
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}
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let mut warnings = payload::check(&payload, &opts.config);
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if template.is_inert() {
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warnings.push(format!(
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"the template {} declares no coursebank markers, so no questions were injected; add \
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`// coursebank:questions` where they belong",
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template.origin
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));
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}
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Ok(Rendered {
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variant: opts.variant,
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origin: template.origin.clone(),
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slots: template.slots(),
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text: template.render(&bodies),
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payload,
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warnings,
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})
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}
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/// Builds the payload without rendering a template.
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///
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/// For writing the questions out as JSON, which is what a hand-written Typst exam
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/// that already calls `json("questions.json")` wants.
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///
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/// # Arguments
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///
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/// * `catalog` - the loaded course.
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/// * `record` - the assessment record.
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/// * `opts` - what to render; only the form and config are consulted.
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///
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/// # Returns
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///
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/// The payload.
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///
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/// # Errors
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///
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/// Returns [`Error::Unresolved`] when a placement references a missing item.
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pub fn build_payload(
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catalog: &Catalog,
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record: &AssessmentFile,
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opts: &Options,
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) -> Result<Payload> {
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payload::build(catalog, record, &opts.form, &opts.config)
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}
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/// The path a course's Typst configuration lives at.
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///
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/// # Arguments
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///
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/// * `layout` - the course layout.
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pub fn config_path(layout: &Layout) -> PathBuf {
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template::dir(layout).join(CONFIG_FILE)
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}
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/// Loads a course's Typst configuration.
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///
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/// # Arguments
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///
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/// * `layout` - the course layout.
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///
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/// # Returns
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///
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/// The parsed config file, or an empty one when `templates/typst.yaml` is absent.
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/// Absence is not an error: a course that has never customized anything should
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/// export without being told to write a config file first.
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///
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/// # Errors
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///
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/// Returns [`Error::Yaml`] when the file exists but does not parse.
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pub fn load_config(layout: &Layout) -> Result<ConfigFile> {
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let path = config_path(layout);
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if path.is_file() {
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crate::yaml::read(&path)
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} else {
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Ok(ConfigFile::default())
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}
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}
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/// Renders the question paper.
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///
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/// Kept so existing callers keep working. New code should use [`render`], which
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/// also reports which template was used and what it warned about.
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///
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/// # Arguments
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///
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/// * `catalog` - the loaded course.
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/// * `record` - the assessment record.
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/// * `opts` - rendering options; the variant is forced to [`Variant::Exam`].
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///
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/// # Returns
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///
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/// A complete Typst document.
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///
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/// # Errors
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///
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/// As [`render`].
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pub fn exam(catalog: &Catalog, record: &AssessmentFile, opts: &Options) -> Result<String> {
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render_variant(catalog, record, opts, Variant::Exam)
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}
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/// Renders the answer key.
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///
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/// # Arguments
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///
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/// * `catalog` - the loaded course.
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/// * `record` - the assessment record.
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/// * `opts` - rendering options; the variant is forced to [`Variant::Key`].
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///
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/// # Returns
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///
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/// A complete Typst document.
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///
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/// # Errors
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///
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/// As [`render`].
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pub fn answer_key(catalog: &Catalog, record: &AssessmentFile, opts: &Options) -> Result<String> {
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render_variant(catalog, record, opts, Variant::Key)
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}
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/// Renders a bubble sheet matching the form.
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///
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/// # Arguments
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///
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/// * `catalog` - the loaded course.
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/// * `record` - the assessment record.
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/// * `opts` - rendering options; the variant is forced to [`Variant::AnswerSheet`].
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///
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/// # Returns
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///
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/// A complete Typst document.
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///
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/// # Errors
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///
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/// As [`render`].
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pub fn bubble_sheet(catalog: &Catalog, record: &AssessmentFile, opts: &Options) -> Result<String> {
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render_variant(catalog, record, opts, Variant::AnswerSheet)
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}
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/// Renders one variant, substituting that variant's default config when the caller
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/// passed the config for a different one.
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fn render_variant(
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catalog: &Catalog,
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record: &AssessmentFile,
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opts: &Options,
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variant: Variant,
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) -> Result<String> {
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let mut opts = opts.clone();
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if opts.variant != variant {
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// The caller asked for a different document than the config describes, so
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// the config's `reveal` almost certainly belongs to the other one. Taking
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// the variant's own default is the safe reading, and the direction that
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// matters is the paper: never inherit a key's `reveal`.
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opts.config = RenderConfig::for_variant(variant);
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opts.variant = variant;
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}
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Ok(render(catalog, record, &opts)?.text)
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use crate::assessment::Placement;
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use crate::select;
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#[test]
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fn options_default_to_the_paper_and_withhold_the_key() {
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let opts = Options::default();
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assert_eq!(opts.variant, Variant::Exam);
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assert!(!opts.config.reveal.shows_key());
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}
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#[test]
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fn an_explicit_template_beats_the_config() {
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let mut opts = Options::default();
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opts.config.template = Some(PathBuf::from("from-config.typ"));
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assert_eq!(opts.template_path(), Some(Path::new("from-config.typ")));
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opts.template = Some(PathBuf::from("from-cli.typ"));
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assert_eq!(opts.template_path(), Some(Path::new("from-cli.typ")));
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}
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#[test]
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fn the_key_reports_letters_as_printed() {
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// Shuffling must relabel the key: if the correct option moves to the third
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// printed position, the key says C.
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let form = Form {
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id: "B".into(),
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seed: 99,
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shuffle_items: false,
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shuffle_options: true,
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};
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let order = select::option_order(&form, "bank::q-1", 4);
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let correct_source = 0usize;
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let printed_position = order.iter().position(|i| *i == correct_source).unwrap();
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let letter = LetterStyle::Upper.label(printed_position);
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assert!(["A", "B", "C", "D"].contains(&letter.as_str()));
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// And it is reproducible.
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let again = select::option_order(&form, "bank::q-1", 4);
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assert_eq!(order, again);
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}
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#[test]
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fn dropped_items_are_not_printed() {
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let record = AssessmentFile {
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schema_version: "1.0".into(),
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assessment: crate::assessment::Assessment {
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id: "e1".into(),
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title: "Exam 1".into(),
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term: None,
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kind: crate::assessment::Kind::Exam,
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date: None,
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platform: crate::assessment::Platform::Paper,
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minutes_allowed: None,
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attempts: None,
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shuffle: None,
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scoring_policy: None,
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instructions: None,
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notes: None,
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},
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blueprint: None,
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forms: Vec::new(),
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items: vec![
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Placement {
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number: 1,
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item: "b::q-1".into(),
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version: None,
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fingerprint: None,
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points: None,
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bonus: false,
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key: vec!["A".into()],
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level: None,
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learning_objectives: Vec::new(),
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credit_overrides: Default::default(),
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dropped: true,
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},
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Placement {
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number: 2,
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item: "b::q-2".into(),
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version: None,
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fingerprint: None,
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points: None,
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bonus: false,
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key: vec!["B".into()],
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level: None,
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learning_objectives: Vec::new(),
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credit_overrides: Default::default(),
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dropped: false,
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},
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],
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};
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let printable: Vec<u32> = select::layout(&record, &Options::default().form)
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.into_iter()
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.filter(|p| !p.dropped)
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.map(|p| p.number)
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.collect();
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assert_eq!(printable, vec![2]);
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}
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}
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