Fields: a count past its number format's range keeps its digits

NUMWORDS, NUMCHARS and REVNUM wrote a count past what the field's \*
number format covers as the format's last value, so a revision number
of 1,000,000 under \* ROMAN showed 50 M's. Such a count now keeps its
digits, as a table formula result does.

crates/engine/src/cmd/references.rs

@@ -1144,10 +1144,13 @@ fn new_property_value(instr: &str) -> Option<String> {
     FieldCode::parse(instr).args.first().map(|a| a.chars().take(255).collect())
 }
 
-/// A count (NUMWORDS, NUMCHARS, REVNUM) in the field's `\*` number format, digits without one,
+/// A count (NUMWORDS, NUMCHARS, REVNUM) in the field's `\*` number format, digits without one or
+/// when the format does not cover the count (see [`super::table_formula::number_format_covers`]),
 /// with the field's capitalization switches.
 fn count_text(instr: &str, n: usize) -> String {
-    let fmt = wordcraft_layout::fields::format_switch(instr).unwrap_or(NumFormat::Decimal);
+    let fmt = wordcraft_layout::fields::format_switch(instr)
+        .filter(|f| super::table_formula::number_format_covers(*f, n as f64))
+        .unwrap_or(NumFormat::Decimal);
     wordcraft_layout::fields::field_number(instr, fmt, u32::try_from(n).unwrap_or(u32::MAX))
 }
 
@@ -1647,6 +1650,18 @@ mod tests {
         assert_eq!((s.doc.core.subject.as_str(), s.doc.core.creator.as_str()), ("Old", "Grace"));
     }
 
+    /// A count the field's number format does not cover keeps its digits.
+    #[test]
+    fn counts_past_the_number_format_keep_their_digits() {
+        let mut doc = wordcraft_doc::Document::from_text("one two three");
+        doc.core.revision = 1_000_000;
+        let codes = [r"REVNUM \* ROMAN", r"REVNUM \* CardText", r"REVNUM \* alphabetic", r"NUMWORDS \* ROMAN"];
+        let (mut s, hdr) = header_fields_session(doc, &codes);
+        s.run("references.updateFields", &json!({})).unwrap();
+        let got: Vec<String> = story_fields(&s, StoryRef::Part(hdr)).into_iter().map(|(_, r)| r).collect();
+        assert_eq!(got, ["1000000", "1000000", "1000000", "III"]);
+    }
+
     /// #1706: `all: true` (printing) updates the whole document even with the caret in a header.
     #[test]
     fn update_fields_all_covers_every_story() {

crates/engine/src/cmd/table_formula.rs

@@ -116,16 +116,23 @@ fn format_switches(switches: &str, value: f64, text: String) -> String {
     use wordcraft_doc::section::NumFormat;
     let unquoted = switches.split('"').step_by(2).collect::<Vec<_>>().join(" ");
     let fmt = wordcraft_layout::fields::format_switch(&unquoted).filter(|f| *f != NumFormat::Decimal);
-    let covers = |fmt: NumFormat| match fmt {
+    match fmt {
+        Some(fmt) if number_format_covers(fmt, value) => wordcraft_layout::fields::field_number(switches, fmt, value as u32),
+        _ => wordcraft_layout::fields::apply_case_switch(switches, text),
+    }
+}
+
+/// Whether the `\*` number format `fmt` writes `value`: a whole number up to 999,999 for CardText
+/// and OrdText, 1 to 50,000 for roman, 1 to 780 for alphabetic, and 0 to `u32::MAX` otherwise.
+pub(crate) fn number_format_covers(fmt: wordcraft_doc::section::NumFormat, value: f64) -> bool {
+    use wordcraft_doc::section::NumFormat;
+    let range = match fmt {
         NumFormat::CardinalText | NumFormat::OrdinalText => 0.0..=999_999.0,
         NumFormat::LowerRoman | NumFormat::UpperRoman => 1.0..=50_000.0,
         NumFormat::LowerLetter | NumFormat::UpperLetter => 1.0..=780.0,
         _ => 0.0..=f64::from(u32::MAX),
     };
-    match fmt {
-        Some(fmt) if value.fract() == 0.0 && covers(fmt).contains(&value) => wordcraft_layout::fields::field_number(switches, fmt, value as u32),
-        _ => wordcraft_layout::fields::apply_case_switch(switches, text),
-    }
+    value.fract() == 0.0 && range.contains(&value)
 }
 
 /// Splits a field's switches (`\#` and `\*`) off its formula: `=SUM(ABOVE) \# "0.00"` gives the