Some documentation and reduce copy/paste (#3917)

* NF: document that cloze number are kept as they are in the field

I needed to know because {{c1 generate card 0 for example. And storing
the card ordinal would have been another consistent choice.

* NF: introduce method that return the cloze number in fields

This slightly reduce code duplication.

* Apply suggestions from code review

rslib/src/cloze.rs

@@ -43,6 +43,7 @@ mod mathjax_caps {
 
 #[derive(Debug)]
 enum Token<'a> {
+    // The parameter is the cloze number as is appears in the field content.
     OpenCloze(u16),
     Text(&'a str),
     CloseCloze,
@@ -114,6 +115,7 @@ enum TextOrCloze<'a> {
 
 #[derive(Debug)]
 struct ExtractedCloze<'a> {
+    // `ordinal` is the cloze number as is appears in the field content.
     ordinal: u16,
     nodes: Vec<TextOrCloze<'a>>,
     hint: Option<&'a str>,
@@ -409,12 +411,14 @@ pub fn expand_clozes_to_reveal_latex(text: &str) -> String {
     buf
 }
 
+// Whether `text` contains any cloze number above 0
 pub(crate) fn contains_cloze(text: &str) -> bool {
     parse_text_with_clozes(text)
         .iter()
         .any(|node| matches!(node, TextOrCloze::Cloze(e) if e.ordinal != 0))
 }
 
+/// Returns the set of cloze number as they appear in the fields's content.
 pub fn cloze_numbers_in_string(html: &str) -> HashSet<u16> {
     let mut set = HashSet::with_capacity(4);
     add_cloze_numbers_in_string(html, &mut set);
@@ -432,11 +436,21 @@ fn add_cloze_numbers_in_text_with_clozes(nodes: &[TextOrCloze], set: &mut HashSe
     }
 }
 
+/// Add to `set` the cloze numbers as they appear in `field`.
 #[allow(clippy::implicit_hasher)]
 pub fn add_cloze_numbers_in_string(field: &str, set: &mut HashSet<u16>) {
     add_cloze_numbers_in_text_with_clozes(&parse_text_with_clozes(field), set)
 }
 
+/// The set of cloze numbers as they appear in any of the fields from `fields`.
+pub fn cloze_number_in_fields(fields: impl IntoIterator<Item: AsRef<str>>) -> HashSet<u16> {
+    let mut set = HashSet::with_capacity(4);
+    for field in fields {
+        add_cloze_numbers_in_string(field.as_ref(), &mut set);
+    }
+    set
+}
+
 fn strip_html_inside_mathjax(text: &str) -> Cow<str> {
     MATHJAX.replace_all(text, |caps: &Captures| -> String {
         format!(

rslib/src/notes/service.rs

@@ -1,8 +1,6 @@
 // Copyright: Ankitects Pty Ltd and contributors
 // License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
-use std::collections::HashSet;
+use crate::cloze::cloze_number_in_fields;
-
-use crate::cloze::add_cloze_numbers_in_string;
 use crate::collection::Collection;
 use crate::decks::DeckId;
 use crate::error;
@@ -128,10 +126,7 @@ impl crate::services::NotesService for Collection {
         &mut self,
         note: anki_proto::notes::Note,
     ) -> error::Result<anki_proto::notes::ClozeNumbersInNoteResponse> {
-        let mut set = HashSet::with_capacity(4);
+        let set = cloze_number_in_fields(note.fields);
-        for field in &note.fields {
-            add_cloze_numbers_in_string(field, &mut set);
-        }
         Ok(anki_proto::notes::ClozeNumbersInNoteResponse {
             numbers: set.into_iter().map(|n| n as u32).collect(),
         })

rslib/src/notetype/cardgen.rs

@@ -11,7 +11,7 @@ use rand::Rng;
 use rand::SeedableRng;
 
 use super::Notetype;
-use crate::cloze::add_cloze_numbers_in_string;
+use crate::cloze::cloze_number_in_fields;
 use crate::notetype::NotetypeKind;
 use crate::prelude::*;
 use crate::template::ParsedTemplate;
@@ -148,10 +148,7 @@ impl<N: Deref<Target = Notetype>> CardGenContext<N> {
         extracted: &ExtractedCardInfo,
     ) -> Vec<CardToGenerate> {
         // gather all cloze numbers
-        let mut set = HashSet::with_capacity(4);
+        let set = cloze_number_in_fields(note.fields());
-        for field in note.fields() {
-            add_cloze_numbers_in_string(field, &mut set);
-        }
         set.into_iter()
             .filter_map(|cloze_ord| {
                 let card_ord = cloze_ord.saturating_sub(1).min(499);

rslib/src/template.rs

@@ -15,7 +15,7 @@ use nom::combinator::map;
 use nom::sequence::delimited;
 use regex::Regex;
 
-use crate::cloze::add_cloze_numbers_in_string;
+use crate::cloze::cloze_number_in_fields;
 use crate::error::AnkiError;
 use crate::error::Result;
 use crate::error::TemplateError;
@@ -673,11 +673,7 @@ pub fn render_card(
 }
 
 fn cloze_is_empty(field_map: &HashMap<&str, Cow<str>>, card_ord: u16) -> bool {
-    let mut set = HashSet::with_capacity(4);
+    !cloze_number_in_fields(field_map.values()).contains(&(card_ord + 1))
-    for field in field_map.values() {
-        add_cloze_numbers_in_string(field.as_ref(), &mut set);
-    }
-    !set.contains(&(card_ord + 1))
 }
 
 // Field requirements