feat: fix exporting to pdf

src/export/practice.rs

@@ -259,7 +259,11 @@ pub fn render(catalog: &Catalog, record: &AssessmentFile, opts: &Options) -> Res
 
 /// The Quarto YAML front matter.
 fn front_matter(course: &CourseFile, record: &AssessmentFile, variant: Variant) -> String {
-    let title = format!("{}: {}", record.assessment.title, variant.title_word());
+    let title = if matches!(variant, Variant::Solutions) {
+        format!("{}: {}", record.assessment.title, variant.title_word())
+    } else {
+        record.assessment.title.clone()
+    };
     let subtitle = format!("{} · {}", course.course.code, course.course.title);
     let mut out = String::from("---\n");
     out.push_str(&format!("title: \"{}\"\n", yaml_quote(&title)));

src/export/site.rs

@@ -329,10 +329,7 @@ fn choice_fragment(course: &CourseFile, placement: &Placement, item: &Item, form
             ));
         }
         if let Some(explanation) = &solution.explanation {
-            out.push_str(&format!(
-                "<p class=\"sol-explain\">{}</p>\n",
-                inline_html(explanation)
-            ));
+            out.push_str(&explain_html(explanation));
         }
     }
 
@@ -377,7 +374,8 @@ fn choice_fragment(course: &CourseFile, placement: &Placement, item: &Item, form
     out
 }
 
-/// An open-response fragment: the model answer, the rubric, accepted variants.
+/// An open-response fragment: the model answer, the explanation, the rubric, and
+/// the accepted variants.
 fn open_fragment(course: &CourseFile, item: &Item) -> Option<String> {
     let solution = item.solution.as_ref().filter(|s| !s.is_empty())?;
     let mut out = String::new();
@@ -389,6 +387,10 @@ fn open_fragment(course: &CourseFile, item: &Item) -> Option<String> {
         ));
     }
 
+    if let Some(explanation) = &solution.explanation {
+        out.push_str(&explain_html(explanation));
+    }
+
     if !solution.rubric.is_empty() {
         let caption = match solution.rubric_points() {
             Some(total) => {
@@ -593,6 +595,18 @@ fn block_html(src: &str) -> String {
         .join("")
 }
 
+/// Renders a solution explanation as one `<p class="sol-explain">` per blank-line-
+/// separated paragraph. A single-paragraph explanation emits exactly one such
+/// paragraph, unchanged from before; a multi-paragraph one keeps its breaks, and
+/// every paragraph carries the class `questions.css` already styles.
+fn explain_html(src: &str) -> String {
+    src.split("\n\n")
+        .map(str::trim)
+        .filter(|p| !p.is_empty())
+        .map(|p| format!("<p class=\"sol-explain\">{}</p>\n", inline_html(p)))
+        .collect()
+}
+
 // --- the encrypted bundle -----
 
 /// The encrypted solutions bundle, matching the `solutions.js` v1 format.
@@ -805,6 +819,10 @@ items:
     learning_objectives: [lo-enthalpy]
     solution:
       model_answer: "From $H = U + PV$ at constant pressure, $q_p = \\Delta H$."
+      explanation: |
+        At constant pressure the pressure-volume work is folded into H, so the heat equals the change in H.
+
+        That is why a calorimeter run at constant pressure reads the enthalpy change directly.
       rubric:
         - { description: "States $H = U + PV$.", points: 1 }
         - { description: "Reaches $q_p = \\Delta H$.", points: 1 }
@@ -914,6 +932,31 @@ items:
         assert!(open.contains("<span class=\"badge\">Also accepted</span>"));
     }
 
+    #[test]
+    fn an_open_fragment_shows_the_model_answer_and_the_explanation() {
+        // Both fields render, in that order, so an open-response solution reads as
+        // the answer followed by the reasoning, the same as a choice fragment. A
+        // multi-paragraph explanation keeps its breaks as separate paragraphs.
+        let cat = catalog("open-explain");
+        let rec = record();
+        let frags = solution_fragments(&cat, &rec, &form()).unwrap();
+        let open = &frags.iter().find(|(id, _)| id == "q-open").unwrap().1;
+        assert!(open.contains("<div class=\"sol-model\">"), "model answer shown:\n{open}");
+        assert_eq!(
+            open.matches("<p class=\"sol-explain\">").count(),
+            2,
+            "each explanation paragraph is its own styled <p>:\n{open}"
+        );
+        assert!(open.contains("folded into H"), "first paragraph present:\n{open}");
+        assert!(
+            open.contains("reads the enthalpy change directly"),
+            "second paragraph present:\n{open}"
+        );
+        let model_at = open.find("sol-model").unwrap();
+        let explain_at = open.find("sol-explain").unwrap();
+        assert!(model_at < explain_at, "model answer comes before the explanation");
+    }
+
     #[test]
     fn inline_html_keeps_math_verbatim_and_escapes_prose() {
         // A subscript inside math survives; angle brackets outside math are escaped.