Prompt file imported from mnpham2101/JapaneseLearn (.github/prompts/speckit.subtask.6-S-4-2.prompt.md). Copyright stays with the author.

Subtask 6.S.4.2 — Rust: propagate is_kanji through exercise_generator and vocabulary lib

Agent: rust-developer
Parent task: 6.S.4
Depends on: 6.S.4.1
Commit: one commit, one logical change

Subtask Goals

After this commit, kanji-front flashcards generated by FlashcardExerciseTransformer carry is_kanji: true. The field flows through FlashcardCardData → vocabulary lib.rs type conversion → FlashcardModel Slint struct. Existing JSON stacks round-trip correctly (is_kanji defaults to false on deserialization if absent). All existing tests pass; kanji-word tests assert is_kanji is correct.

Subtask Technical Approach

Files to be Changed

exercise_generator/src/models.rs

#[derive(Debug, Clone)]
pub struct FlashcardCardData {
    pub front: String,
    pub back: String,
    pub known: bool,
    pub is_kanji: bool,   // ← add this field
}

flashcard_transformer.rs — make_cards()

In the make_cards() function, the spelling card gets is_kanji: false and the kanji card gets is_kanji: true:

fn make_cards(word: &VocabularyWord) -> Vec<FlashcardCardData> {
    let back = format_explanation(word);
    let mut cards = vec![FlashcardCardData {
        front: word.spelling.clone(),
        back: back.clone(),
        known: false,
        is_kanji: false,   // spelling front — not kanji
    }];
    if let Some(kanji) = &word.kanji {
        cards.push(FlashcardCardData {
            front: kanji.clone(),
            back,
            known: false,
            is_kanji: true,   // kanji front — large brush font
        });
    }
    cards
}

Update existing inline tests to assert is_kanji:

#[test]
fn spelling_only_produces_one_card() {
    // ...
    assert!(!stacks[0].cards[0].is_kanji);
}

#[test]
fn kanji_word_produces_two_cards_sharing_same_back() {
    // ...
    assert!(!stacks[0].cards[0].is_kanji);  // spelling card
    assert!(stacks[0].cards[1].is_kanji);   // kanji card
}

lib/flashcard/src/lib.rs — CardData persistence

Add is_kanji to the JSON persistence struct with a serde default so existing saved stacks (without the field) deserialize correctly:

#[derive(serde::Serialize, serde::Deserialize)]
struct CardData {
    jap_obj: String,
    explanation: String,
    known: bool,
    #[serde(default)]
    is_kanji: bool,   // ← add with default=false for backwards compat
}

Update to_stack_data() to copy the field:

.map(|c| CardData {
    jap_obj: c.jap_obj.to_string(),
    explanation: c.explanation.to_string(),
    known: c.known,
    is_kanji: c.is_kanji,   // ← add
})

Update from_stack_data() to populate the Slint model field:

.map(|c| flashcard::FlashcardModel {
    jap_obj: c.jap_obj.into(),
    explanation: c.explanation.into(),
    known: c.known,
    is_kanji: c.is_kanji,   // ← add
})

lib/vocabulary/src/lib.rs — FlashcardCardData → FlashcardModel

Locate the conversion in the on_generate_exercises_clicked handler where FlashcardCardData is mapped to flashcard::FlashcardModel. Add is_kanji:

flashcard::FlashcardModel {
    jap_obj: card.front.clone().into(),
    explanation: card.back.clone().into(),
    known: card.known,
    is_kanji: card.is_kanji,   // ← add
}

Verification

cargo test -p exercise_generator          # all 4 transformer tests pass
cargo build --bin japanese_learn          # zero errors
cargo clippy --bin japanese_learn         # zero warnings
cargo test -p flashcard-tests             # all 8 CRUD tests pass

Generate flashcards from a vocabulary lesson that has kanji words. Inspect the resulting flashcard stack: kanji-front cards should display extra-large text with MS Mincho font.