Add units of measure and fractional quantities to rate lines

Quantities can now be time, count, distance, area, weight or volume, or a custom unit, instead of only
second/minute/hour/session/unit.

- Registry in src/lib/units.ts (mirrored in src-tauri/src/units.rs): grouped built-in units plus a custom unit of 1-12
  characters. A rate line's unit is validated when an invoice or a preset is saved; migration M12 drops the old unit
  allow-list from item_presets and keeps every row.
- Time is typed as h:mm: "4:30" hours counts as 4.5, "4:20" as 4.333... (kept exact, so rate x quantity rounds once, the
  same in TypeScript and Rust). Other units take plain decimals up to 3 places. A bad quantity blocks issuing.
- The PDF quantity column shows the unit ("4.5 hr", "12.75 km"); the rate keeps "per hour" / "/hr". RenderItem carries
  priceText, perText and rateShort, so no template parses the rate text with a regex over five hard-coded units.
- Quantity columns are sized from the widest word once a quantity with its unit is wider than 72 pt, so one long
  custom unit cannot squeeze the description (the serenity and citrus-split tables overflowed in the new fixture).
  Classic's quantity column is now content-sized.
- ERPNext: the default UOM map comes from the registry, with fractional-capable UOMs for time, distance, area, weight
  and volume. A custom unit is sent as Nos. A quantity that is not exact to 3 decimals (4:20 hours) is still refused for
  push, as before.
- Goldens and template thumbnails regenerated; the template harness has a "units" fixture with the longest texts.

Claude-Session: https://claude.ai/code/session_01PZypiWDfMkDTeEPeXjRhW5

src-tauri/src/commands/invoice.rs

@@ -7,6 +7,7 @@ use super::payments::{derive_summary, summary_for, today_ist};
 use crate::models::{
     BankAccount, DraftSummary, Invoice, InvoiceInput, InvoiceItem, InvoiceSummary, PaymentSummary, Settings,
 };
+use crate::units;
 use crate::AppState;
 use chrono::NaiveDate;
 use rusqlite::{named_params, params, Connection, OptionalExtension, Row};
@@ -130,6 +131,15 @@ fn parse_date(label: &str, value: &str) -> Result<(), String> {
 /// overflow integer paise arithmetic.
 const MAX_LINE_RUPEES: f64 = 1e11;
 
+/// The unit written to the database. A fixed-amount line has no unit of its own, so whatever the form held is not kept.
+fn stored_unit(item: &InvoiceItem) -> String {
+    if item.mode == "rate" {
+        units::normalize(&item.unit)
+    } else {
+        "unit".to_string()
+    }
+}
+
 fn validate_items(items: &[InvoiceItem]) -> Result<(), String> {
     if items.is_empty() {
         return Err("Add at least one line item".into());
@@ -145,6 +155,7 @@ fn validate_items(items: &[InvoiceItem]) -> Result<(), String> {
                 if item.quantity > MAX_LINE_RUPEES {
                     return Err(format!("Line {n}: quantity is too large"));
                 }
+                units::validate(&item.unit).map_err(|e| format!("Line {n}: {e}"))?;
                 let amount = gst::line_amount_paise(item);
                 if amount <= 0 {
                     return Err(format!("Line {n}: amount must be greater than zero"));
@@ -427,7 +438,7 @@ pub fn issue_invoice_impl(
                 item.description,
                 item.mode,
                 item.rate,
-                item.unit,
+                stored_unit(item),
                 item.quantity,
                 paise_to_rupees(gst::line_amount_paise(item)),
                 i as i64,
@@ -854,6 +865,43 @@ mod tests {
         assert_eq!(inv.items[1].hsn_sac, "");
     }
 
+    #[test]
+    fn lines_can_use_any_unit_and_fractional_quantities() {
+        let mut conn = registered();
+        let inv = issue(
+            &mut conn,
+            input(json!({
+                "items": [
+                    {"description": "Travel", "mode": "rate", "rate": 18.0, "quantity": 12.75, "unit": "km"},
+                    {"description": "Studio", "mode": "rate", "rate": 1200.0, "quantity": 4.0 + 1.0 / 3.0, "unit": "HOUR"},
+                    {"description": "Parcels", "mode": "rate", "rate": 99.5, "quantity": 3.0, "unit": " bundle "},
+                    {"description": "Fee", "mode": "fixed", "amount": 10.0, "unit": "not a unit;"},
+                ],
+            })),
+        )
+        .unwrap();
+        let units: Vec<&str> = inv.items.iter().map(|i| i.unit.as_str()).collect();
+        assert_eq!(units, ["km", "hour", "bundle", "unit"]);
+        let amounts: Vec<f64> = inv.items.iter().map(|i| i.amount).collect();
+        // 18 x 12.75 = 229.50; 1200 x 4h20m = 5200.00 (one rounding, on the exact quantity); 99.50 x 3 = 298.50.
+        assert_eq!(amounts, [229.5, 5200.0, 298.5, 10.0]);
+    }
+
+    #[test]
+    fn a_rate_line_with_a_bad_unit_is_refused_and_the_counter_stays() {
+        let mut conn = registered();
+        for bad in ["", "   ", "thirteen char", "x;y", "\u{20b9}"] {
+            let err = issue(
+                &mut conn,
+                input(json!({"items": [{"description": "Work", "mode": "rate", "rate": 10.0, "quantity": 1.0, "unit": bad}]})),
+            )
+            .unwrap_err();
+            assert!(err.starts_with("Line 1: "), "{bad:?}: {err}");
+        }
+        assert_eq!(next_number(&conn), 1);
+        assert_eq!(invoice_count(&conn), 0);
+    }
+
     #[test]
     fn tax_type_mismatch_is_rejected_and_the_counter_stays() {
         let mut conn = registered();

src-tauri/src/commands/presets.rs

@@ -1,10 +1,10 @@
 use crate::models::ItemPreset;
+use crate::units;
 use crate::AppState;
 use rusqlite::{params, Connection, Row};
 use tauri::State;
 
 const MODES: &[&str] = &["fixed", "rate"];
-const UNITS: &[&str] = &["second", "minute", "hour", "session", "unit"];
 /// Upper bound on a preset amount (paise); keeps later integer-paise arithmetic far from overflow.
 const MAX_RATE_PAISE: i64 = 100_000_000_000;
 
@@ -45,9 +45,8 @@ pub fn save_preset_impl(conn: &Connection, preset: ItemPreset) -> Result<ItemPre
     if !MODES.contains(&preset.mode.as_str()) {
         return Err(format!("Unknown line type \"{}\"", preset.mode));
     }
-    if !UNITS.contains(&preset.unit.as_str()) {
-        return Err(format!("Unknown unit \"{}\"", preset.unit));
-    }
+    units::validate(&preset.unit)?;
+    let unit = units::normalize(&preset.unit);
     if !(0..=MAX_RATE_PAISE).contains(&preset.rate_paise) {
         return Err("Amount is out of range".into());
     }
@@ -58,7 +57,7 @@ pub fn save_preset_impl(conn: &Connection, preset: ItemPreset) -> Result<ItemPre
                 .execute(
                     "UPDATE item_presets SET description=?1, hsn_sac=?2, mode=?3, unit=?4, rate_paise=?5, sort_order=?6
                      WHERE id=?7",
-                    params![description, hsn, preset.mode, preset.unit, preset.rate_paise, preset.sort_order, id],
+                    params![description, hsn, preset.mode, unit, preset.rate_paise, preset.sort_order, id],
                 )
                 .map_err(|e| e.to_string())?;
             if n == 0 {
@@ -74,7 +73,7 @@ pub fn save_preset_impl(conn: &Connection, preset: ItemPreset) -> Result<ItemPre
                     description,
                     hsn,
                     preset.mode,
-                    preset.unit,
+                    unit,
                     preset.rate_paise,
                     preset.sort_order,
                     chrono::Utc::now().to_rfc3339()
@@ -156,6 +155,18 @@ mod tests {
         delete_preset_impl(&conn, 12345).unwrap();
     }
 
+    #[test]
+    fn units_beyond_the_original_five_are_stored_as_given() {
+        let conn = open_in_memory().unwrap();
+        for (typed, stored) in [("km", "km"), ("SQFT", "sqft"), ("  bundle ", "bundle"), ("sq.ft/day", "sq.ft/day")] {
+            let mut p = preset(typed);
+            p.mode = "rate".into();
+            p.unit = typed.into();
+            p.rate_paise = 5_000;
+            assert_eq!(save_preset_impl(&conn, p).unwrap().unit, stored, "{typed}");
+        }
+    }
+
     #[test]
     fn validation_rejects_bad_presets() {
         let conn = open_in_memory().unwrap();
@@ -166,9 +177,11 @@ mod tests {
         let mut p = preset("X");
         p.mode = "weird".into();
         assert!(save_preset_impl(&conn, p).is_err());
-        let mut p = preset("X");
-        p.unit = "decade".into();
-        assert!(save_preset_impl(&conn, p).is_err());
+        for bad in ["", "   ", "far too long a unit", "bad;unit", "₹"] {
+            let mut p = preset("X");
+            p.unit = bad.into();
+            assert!(save_preset_impl(&conn, p).is_err(), "{bad:?}");
+        }
         let mut ghost = preset("Ghost");
         ghost.id = Some(77);
         assert!(save_preset_impl(&conn, ghost).is_err());

src-tauri/src/db.rs

@@ -10,7 +10,7 @@ const MAX_BACKUPS: usize = 10;
 const BACKUP_PREFIX: &str = "voiced-pre-v";
 
 /// Highest schema version, i.e. the number of entries in `migrations()`.
-pub(crate) const LATEST_VERSION: i64 = 11;
+pub(crate) const LATEST_VERSION: i64 = 12;
 
 #[derive(Debug, thiserror::Error)]
 pub enum DbError {
@@ -345,6 +345,27 @@ DROP TABLE erpnext_sync;
 ALTER TABLE erpnext_sync_new RENAME TO erpnext_sync;
 "#;
 
+/// Version 12: `item_presets.unit` no longer lists five units. Units of measure now cover time, distance, area, weight and
+/// volume, and a preset may carry a custom unit, so the allow-list becomes a length check and src/units.rs does the rest.
+/// SQLite cannot alter a CHECK constraint, so the table is rebuilt; every M7/M10 row is copied over with its id.
+const M12: &str = r#"
+CREATE TABLE item_presets_new (
+    id                INTEGER PRIMARY KEY AUTOINCREMENT,
+    description       TEXT NOT NULL,
+    hsn_sac           TEXT NOT NULL DEFAULT '',
+    mode              TEXT NOT NULL DEFAULT 'fixed' CHECK (mode IN ('fixed', 'rate')),
+    unit              TEXT NOT NULL DEFAULT 'unit' CHECK (length(trim(unit)) BETWEEN 1 AND 12),
+    rate_paise        INTEGER NOT NULL DEFAULT 0 CHECK (rate_paise >= 0),
+    sort_order        INTEGER NOT NULL DEFAULT 0,
+    created_at        TEXT NOT NULL,
+    erpnext_item_code TEXT
+);
+INSERT INTO item_presets_new (id, description, hsn_sac, mode, unit, rate_paise, sort_order, created_at, erpnext_item_code)
+    SELECT id, description, hsn_sac, mode, unit, rate_paise, sort_order, created_at, erpnext_item_code FROM item_presets;
+DROP TABLE item_presets;
+ALTER TABLE item_presets_new RENAME TO item_presets;
+"#;
+
 fn migrations() -> Migrations<'static> {
     Migrations::new(vec![
         M::up(SCHEMA),
@@ -358,6 +379,7 @@ fn migrations() -> Migrations<'static> {
         M::up(M9),
         M::up(M10),
         M::up(M11),
+        M::up(M12),
     ])
 }
 
@@ -950,7 +972,7 @@ CREATE INDEX IF NOT EXISTS idx_invoices_created ON invoices(created_at DESC);
         assert!(conn.execute("UPDATE erpnext_sync SET status = 'conflict'", []).is_err());
 
         migrations().to_latest(&mut conn).unwrap();
-        assert_eq!(user_version(&conn), 11);
+        assert_eq!(user_version(&conn), LATEST_VERSION);
         let row: (String, i64, String, String, String, Option<String>) = conn
             .query_row(
                 "SELECT remote_name, remote_docstatus, status, payload_hash, attachment_sha256, synced_at FROM erpnext_sync WHERE invoice_id = 1",
@@ -968,6 +990,49 @@ CREATE INDEX IF NOT EXISTS idx_invoices_created ON invoices(created_at DESC);
         assert!(conn.execute("INSERT INTO erpnext_sync (invoice_id, status) VALUES (1, 'error')", []).is_err());
     }
 
+    #[test]
+    fn m12_rebuilds_item_presets_keeping_rows_and_allowing_new_units() {
+        let mut conn = Connection::open_in_memory().unwrap();
+        let v11 = vec![
+            M::up(SCHEMA), M::up(M2), M::up(M3), M::up(M4), M::up(M5), M::up(M6), M::up(M7), M::up(M8), M::up(M9), M::up(M10), M::up(M11),
+        ];
+        Migrations::new(v11).to_latest(&mut conn).unwrap();
+        assert_eq!(user_version(&conn), 11);
+        conn.execute(
+            "INSERT INTO item_presets (description, hsn_sac, mode, unit, rate_paise, sort_order, created_at, erpnext_item_code)
+             VALUES ('Studio', '998397', 'rate', 'hour', 150050, 3, 'then', 'ITEM-1'), ('Fee', '', 'fixed', 'unit', 500000, 0, 'then', NULL)",
+            [],
+        )
+        .unwrap();
+        assert!(conn.execute("INSERT INTO item_presets (description, unit, created_at) VALUES ('X', 'km', 'now')", []).is_err());
+
+        migrations().to_latest(&mut conn).unwrap();
+        assert_eq!(user_version(&conn), 12);
+        let rows: Vec<(i64, String, String, String, String, i64, i64, String, Option<String>)> = conn
+            .prepare("SELECT id, description, hsn_sac, mode, unit, rate_paise, sort_order, created_at, erpnext_item_code FROM item_presets ORDER BY id")
+            .unwrap()
+            .query_map([], |r| {
+                Ok((r.get(0)?, r.get(1)?, r.get(2)?, r.get(3)?, r.get(4)?, r.get(5)?, r.get(6)?, r.get(7)?, r.get(8)?))
+            })
+            .unwrap()
+            .collect::<Result<_, _>>()
+            .unwrap();
+        assert_eq!(
+            rows,
+            vec![
+                (1, "Studio".into(), "998397".into(), "rate".into(), "hour".into(), 150050, 3, "then".into(), Some("ITEM-1".into())),
+                (2, "Fee".into(), "".into(), "fixed".into(), "unit".into(), 500000, 0, "then".into(), None),
+            ]
+        );
+        // New units and custom text are allowed; an empty or over-long unit is not; ids keep counting up.
+        conn.execute("INSERT INTO item_presets (description, unit, created_at) VALUES ('Travel', 'km', 'now')", []).unwrap();
+        conn.execute("INSERT INTO item_presets (description, unit, created_at) VALUES ('Parcel', 'bundle', 'now')", []).unwrap();
+        assert!(conn.execute("INSERT INTO item_presets (description, unit, created_at) VALUES ('X', '', 'now')", []).is_err());
+        assert!(conn.execute("INSERT INTO item_presets (description, unit, created_at) VALUES ('X', 'thirteen char', 'now')", []).is_err());
+        let last: i64 = conn.query_row("SELECT MAX(id) FROM item_presets", [], |r| r.get(0)).unwrap();
+        assert_eq!(last, 4);
+    }
+
     fn build_v1_database(path: &Path) {
         let conn = Connection::open(path).unwrap();
         conn.execute_batch(V1_SCHEMA).unwrap();

src-tauri/src/integrations/erpnext/config.rs

@@ -61,18 +61,9 @@ impl NamingMode {
 }
 
 /// Voiced line unit to ERPNext UOM. Whole-number UOMs such as "Nos" reject fractional quantities,
-/// which is why hours and minutes map to their own UOMs.
+/// which is why hours, minutes, kilometres and the like map to their own UOMs (see `units::KNOWN`).
 pub fn default_uom_map() -> BTreeMap<String, String> {
-    [
-        ("second", "Second"),
-        ("minute", "Minute"),
-        ("hour", "Hour"),
-        ("session", "Nos"),
-        ("unit", "Nos"),
-    ]
-    .iter()
-    .map(|(k, v)| (k.to_string(), v.to_string()))
-    .collect()
+    crate::units::KNOWN.iter().map(|(id, uom)| (id.to_string(), uom.to_string())).collect()
 }
 
 /// Everything stored for the integration, secret included. Backend-only.

src-tauri/src/lib.rs

@@ -5,6 +5,7 @@ mod integrations;
 mod logo;
 mod models;
 mod selftest;
+mod units;
 
 use rusqlite::Connection;
 use std::path::{Path, PathBuf};

src-tauri/src/units.rs

@@ -0,0 +1,120 @@
+//! Units of measure for rate × quantity lines. Mirrors src/lib/units.ts: the ids below are stored in
+//! invoices and presets, and any other text that passes `validate` is a custom unit stored as typed.
+
+/// Built-in unit ids with the ERPNext UOM each one maps to by default. Whole-number UOMs ("Nos", "Set")
+/// reject fractional quantities, so units that are usually fractional map to UOMs that allow them.
+pub const KNOWN: &[(&str, &str)] = &[
+    ("unit", "Nos"),
+    ("piece", "Nos"),
+    ("set", "Set"),
+    ("session", "Nos"),
+    ("second", "Second"),
+    ("minute", "Minute"),
+    ("hour", "Hour"),
+    ("day", "Day"),
+    ("week", "Week"),
+    ("month", "Month"),
+    ("km", "Kilometer"),
+    ("m", "Meter"),
+    ("sqft", "Square Foot"),
+    ("sqm", "Square Meter"),
+    ("kg", "Kg"),
+    ("litre", "Litre"),
+];
+
+/// Longest custom unit; it lands in a measured PDF column.
+pub const MAX_CUSTOM_LEN: usize = 12;
+
+pub fn is_known(unit: &str) -> bool {
+    KNOWN.iter().any(|(id, _)| *id == unit)
+}
+
+/// The ERPNext UOM that suits a built-in unit.
+pub fn default_uom(unit: &str) -> Option<&'static str> {
+    KNOWN.iter().find(|(id, _)| *id == unit).map(|(_, uom)| *uom)
+}
+
+fn custom_problem(text: &str) -> Option<String> {
+    let t = text.trim();
+    if t.is_empty() {
+        return Some("a unit is required".into());
+    }
+    if t.chars().count() > MAX_CUSTOM_LEN {
+        return Some(format!("a custom unit has at most {MAX_CUSTOM_LEN} characters"));
+    }
+    let mut chars = t.chars();
+    let first_ok = chars.next().is_some_and(|c| c.is_ascii_alphanumeric());
+    if !first_ok || !chars.all(|c| c.is_ascii_alphanumeric() || matches!(c, ' ' | '.' | '/' | '-')) {
+        return Some("a unit may use letters, digits, spaces, . / and - only".into());
+    }
+    None
+}
+
+/// The unit as it is stored: trimmed, and a built-in id in lower case. An empty value is the generic unit.
+pub fn normalize(unit: &str) -> String {
+    let t = unit.trim();
+    if t.is_empty() {
+        return "unit".to_string();
+    }
+    let lower = t.to_ascii_lowercase();
+    if is_known(&lower) {
+        lower
+    } else {
+        t.to_string()
+    }
+}
+
+/// Checks a unit that is about to be stored. Errors read as `Unit "x": <problem>`.
+pub fn validate(unit: &str) -> Result<(), String> {
+    if unit.trim().is_empty() {
+        return Err("A unit is required".to_string());
+    }
+    if is_known(&normalize(unit)) {
+        return Ok(());
+    }
+    match custom_problem(unit) {
+        None => Ok(()),
+        Some(p) => Err(format!("Unit \"{}\": {p}", unit.trim())),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn known_units_are_accepted_in_any_case() {
+        for (id, _) in KNOWN {
+            assert!(validate(id).is_ok(), "{id}");
+        }
+        assert_eq!(normalize(" HOUR "), "hour");
+        assert_eq!(normalize(""), "unit");
+    }
+
+    #[test]
+    fn custom_units_follow_the_same_rules_as_the_ui() {
+        assert!(validate("bundle").is_ok());
+        assert!(validate("sq.ft/day").is_ok());
+        assert_eq!(normalize("  bundle "), "bundle");
+        assert!(validate("a".repeat(13).as_str()).is_err());
+        assert!(validate("₹").is_err());
+        assert!(validate("-x").is_err());
+        assert!(validate("").is_err());
+        assert!(validate("   ").is_err());
+        assert!(validate("bad;drop").is_err());
+    }
+
+    #[test]
+    fn the_original_five_ids_are_unchanged() {
+        for id in ["second", "minute", "hour", "session", "unit"] {
+            assert!(is_known(id), "{id}");
+        }
+    }
+
+    #[test]
+    fn fractional_units_do_not_map_to_whole_number_uoms() {
+        for id in ["second", "minute", "hour", "day", "week", "month", "km", "m", "sqft", "sqm", "kg", "litre"] {
+            assert_ne!(default_uom(id), Some("Nos"), "{id}");
+        }
+    }
+}