fix: a size worked out from a bare diameter keeps its unit when the design's units change (#716) (#779)

A size typed as a bare diameter now keeps the design's length unit, so it no longer changes when the design's units change. Fixes #716.

crates/engine/src/derived_units_tests.rs

@@ -0,0 +1,230 @@
+//! Sizes a command works out from what it was given keep the meaning those inputs had when the
+//! design's units change (#716): a sphere or a cylinder made with a bare `diameter`, a coil's
+//! pitch or revolutions from its height, a box placed by its centre, a Press Pull. A radius from
+//! a bare diameter used to be stored as `(20) / 2`: a unit-less expression that is not a bare
+//! number is read in the design's units of the moment, so switching a millimetre design to
+//! inches made such a sphere 25.4 times larger.
+
+use std::f64::consts::PI;
+
+use serde_json::{Value, json};
+
+use crate::Session;
+
+fn run(s: &mut Session, id: &str, p: Value) -> Value {
+    match s.execute(id, &p) {
+        Ok(v) => v,
+        Err(e) => panic!("{id} {p}: {e}"),
+    }
+}
+
+fn rel(a: f64, b: f64) -> f64 {
+    (a - b).abs() / b.abs().max(1e-12)
+}
+
+/// A body's volume (mm³) and bounding box (min x, y, z, max x, y, z in mm).
+#[derive(Debug, Clone, Copy)]
+struct Shape {
+    volume: f64,
+    bbox: [f64; 6],
+}
+
+impl Shape {
+    fn size(&self, axis: usize) -> f64 {
+        self.bbox[axis + 3] - self.bbox[axis]
+    }
+    fn same(&self, other: &Shape) -> bool {
+        rel(self.volume, other.volume) < 1e-9 && self.bbox.iter().zip(&other.bbox).all(|(a, b)| (a - b).abs() < 1e-7)
+    }
+}
+
+/// Every body by name.
+fn shapes(s: &mut Session) -> Vec<(String, Shape)> {
+    measured(s, json!({}))
+}
+
+fn measured(s: &mut Session, p: Value) -> Vec<(String, Shape)> {
+    let m = run(s, "inspect.measure", p);
+    let bodies = m["bodies"].as_array().cloned().unwrap_or_default();
+    bodies
+        .iter()
+        .map(|b| {
+            let c = |k: &str, i: usize| b["bbox"][k][i].as_f64().unwrap_or(f64::NAN);
+            let bbox = [c("min", 0), c("min", 1), c("min", 2), c("max", 0), c("max", 1), c("max", 2)];
+            (b["name"].as_str().unwrap_or_default().to_string(), Shape { volume: b["volume_mm3"].as_f64().unwrap_or(f64::NAN), bbox })
+        })
+        .collect()
+}
+
+/// One body, measured alone.
+fn shape(s: &mut Session, body: &str) -> Shape {
+    measured(s, json!({ "bodies": [body] })).into_iter().next().map(|(_, x)| x).unwrap_or_else(|| panic!("no body {body}"))
+}
+
+/// Switch the design to each unit in turn; every body keeps its volume and its bounding box.
+fn keeps_shape_through(s: &mut Session, units: &[&str]) {
+    let before = shapes(s);
+    assert!(!before.is_empty());
+    for u in units {
+        let r = run(s, "document.units", json!({ "units": u }));
+        let now = shapes(s);
+        assert_eq!(now.len(), before.len(), "{u}: {r}");
+        for ((name, a), (_, b)) in before.iter().zip(&now) {
+            assert!(a.same(b), "{name} after switching to {u} ({r}): {a:?} became {b:?}");
+        }
+    }
+}
+
+/// The expressions of a feature's inputs.
+fn inputs(s: &Session, feature: usize) -> Vec<String> {
+    s.doc.features.get(feature).map(|f| f.kind.inputs().into_iter().map(|(_, e, _)| e).collect()).unwrap_or_default()
+}
+
+#[test]
+fn bare_diameters_keep_their_size_when_the_units_change() {
+    let mut s = Session::default();
+    run(&mut s, "solid.sphere", json!({"diameter": 20, "body_name": "Ball"}));
+    run(&mut s, "solid.cylinder", json!({"diameter": 20, "height": 10, "base": [50, 0, 0], "body_name": "Can"}));
+    let ball = shape(&mut s, "Ball");
+    assert!(rel(ball.volume, 4.0 / 3.0 * PI * 1000.0) < 1e-3, "{ball:?}");
+    // The bounding box comes from the tessellation: a little inside the surface.
+    assert!((ball.size(0) - 20.0).abs() < 1e-3 && (ball.bbox[0] + 10.0).abs() < 1e-3, "{ball:?}");
+    let can = shape(&mut s, "Can");
+    assert!(rel(can.volume, PI * 100.0 * 10.0) < 1e-3, "{can:?}");
+    assert!((can.bbox[0] - 40.0).abs() < 1e-3 && (can.bbox[3] - 60.0).abs() < 1e-3 && (can.size(2) - 10.0).abs() < 1e-6, "{can:?}");
+    keeps_shape_through(&mut s, &["in", "cm", "ft", "mm", "in"]);
+    // The radius says what the diameter was, with the unit it was typed in.
+    assert_eq!(inputs(&s, 0), ["(20 mm) / 2"]);
+    assert_eq!(inputs(&s, 1), ["(20 mm) / 2", "10"]);
+}
+
+#[test]
+fn bare_diameters_typed_in_an_inch_design_mean_inches() {
+    let mut s = Session::default();
+    run(&mut s, "document.units", json!({"units": "in"}));
+    run(&mut s, "solid.sphere", json!({"diameter": 2, "body_name": "Ball"}));
+    // The base is a point: its bare numbers are millimetres.
+    run(&mut s, "solid.cylinder", json!({"diameter": 1, "height": 2, "base": [100, 0, 0], "body_name": "Can"}));
+    let ball = shape(&mut s, "Ball");
+    assert!(rel(ball.volume, 4.0 / 3.0 * PI * 25.4f64.powi(3)) < 1e-3, "{ball:?}");
+    assert!((ball.size(0) - 50.8).abs() < 1e-3, "{ball:?}");
+    let can = shape(&mut s, "Can");
+    assert!(rel(can.volume, PI * 12.7 * 12.7 * 50.8) < 1e-3, "{can:?}");
+    assert!((can.bbox[0] - 87.3).abs() < 1e-3 && (can.size(2) - 50.8).abs() < 1e-6, "{can:?}");
+    keeps_shape_through(&mut s, &["mm", "cm", "in"]);
+}
+
+/// A body's extent: the diagonal of its vertices' bounding box. Measuring a coil takes seconds;
+/// this does not.
+fn extent(s: &Session, body: &str) -> f64 {
+    s.model.state().body(body).map_or(f64::NAN, |b| b.body.size())
+}
+
+#[test]
+fn coil_pitch_and_revolutions_keep_their_size_when_the_units_change() {
+    use std::f64::consts::TAU;
+    let mut s = Session::default();
+    // Height and revolutions give the pitch.
+    run(&mut s, "solid.coil", json!({"diameter": 40, "revolutions": 2, "height": 16, "section_size": 4, "body_name": "A"}));
+    // Height and pitch give the revolutions: a height with its unit next to a bare pitch, both
+    // millimetres here.
+    run(&mut s, "solid.coil", json!({"diameter": 40, "height": "16 mm", "pitch": 8, "section_size": 4, "base": [100, 0, 0], "body_name": "B"}));
+    let made = shapes(&mut s);
+    let want = PI * 4.0 * TAU * 20.0 * 2.0;
+    for (body, x) in &made {
+        assert!(rel(x.volume, want) < 1e-3, "{body}: {x:?}");
+        assert!((x.size(2) - made[0].1.size(2)).abs() < 1e-6, "{body} is as tall as A: {made:?}");
+    }
+    assert_eq!(inputs(&s, 0)[1], "(16 mm) / (2)", "A's pitch");
+    assert_eq!(inputs(&s, 1)[2], "(16 mm) / (8 mm)", "B's revolutions");
+    let sizes = |s: &Session| [extent(s, "A"), extent(s, "B")];
+    let before = sizes(&s);
+    for u in ["in", "cm", "mm"] {
+        run(&mut s, "document.units", json!({ "units": u }));
+        let now = sizes(&s);
+        assert!(now.iter().zip(&before).all(|(a, b)| rel(*a, *b) < 1e-9), "{u}: {before:?} became {now:?}");
+    }
+    // In an inch design the same bare numbers are inches.
+    let mut s = Session::default();
+    run(&mut s, "document.units", json!({"units": "in"}));
+    run(&mut s, "solid.coil", json!({"diameter": 2, "revolutions": 2, "height": 0.8, "section_size": 0.2, "body_name": "A"}));
+    let a = shape(&mut s, "A");
+    assert!(rel(a.volume, PI * 2.54f64.powi(2) * TAU * 25.4 * 2.0) < 1e-3, "{a:?}");
+    let before = extent(&s, "A");
+    run(&mut s, "document.units", json!({"units": "mm"}));
+    assert!(rel(extent(&s, "A"), before) < 1e-9, "{before} became {}", extent(&s, "A"));
+}
+
+#[test]
+fn a_box_placed_by_its_centre_reads_its_sizes_in_the_design_units() {
+    // An inch design: bare sizes are inches, the centre's bare numbers millimetres.
+    let mut s = Session::default();
+    run(&mut s, "document.units", json!({"units": "in"}));
+    run(&mut s, "solid.box", json!({"length": 2, "width": 1, "height": 1, "center": [0, 0, 0], "body_name": "A"}));
+    run(&mut s, "solid.box", json!({"length": 2, "width": 1, "height": 1, "center": ["10 mm", 100, 0], "body_name": "B"}));
+    let a = shape(&mut s, "A");
+    assert!((a.bbox[0] + 25.4).abs() < 1e-6 && (a.bbox[3] - 25.4).abs() < 1e-6 && (a.bbox[1] + 12.7).abs() < 1e-6, "{a:?}");
+    let b = shape(&mut s, "B");
+    assert!((b.bbox[0] + 15.4).abs() < 1e-6 && (b.bbox[3] - 35.4).abs() < 1e-6 && (b.bbox[1] - 87.3).abs() < 1e-6, "{b:?}");
+    keeps_shape_through(&mut s, &["mm", "in"]);
+    // A millimetre design: a centre in inches and a bare size in millimetres.
+    let mut s = Session::default();
+    run(&mut s, "solid.box", json!({"length": 1, "width": 1, "height": 1, "center": ["0.5 in", 0, 0], "body_name": "C"}));
+    let c = shape(&mut s, "C");
+    assert!((c.bbox[0] - 12.2).abs() < 1e-6 && (c.bbox[3] - 13.2).abs() < 1e-6, "{c:?}");
+    keeps_shape_through(&mut s, &["in", "mm"]);
+}
+
+#[test]
+fn press_pull_keeps_its_distance_when_the_units_change() {
+    // A face pushed in: the cut's depth is the distance's size.
+    let mut s = Session::default();
+    run(&mut s, "solid.box", json!({"length": 40, "width": 30, "height": 20, "body_name": "Block"}));
+    run(&mut s, "solid.press_pull", json!({"face": [20, 15, 20], "distance": -5}));
+    assert!(rel(shape(&mut s, "Block").volume, 40.0 * 30.0 * 15.0) < 1e-9);
+    keeps_shape_through(&mut s, &["in", "mm"]);
+    // A fillet's face: its radius grows by the distance.
+    let mut s = Session::default();
+    run(&mut s, "solid.box", json!({"length": 40, "width": 30, "height": 20, "body_name": "Block"}));
+    run(&mut s, "solid.fillet", json!({"edges": [[40, 0, 10]], "radius": 3, "name": "Round"}));
+    let corner = |r: f64| (4.0 - PI) * r * r / 4.0 * 20.0;
+    let on = |r: f64| {
+        let d = r - r / 2f64.sqrt();
+        json!([40.0 - d, d, 10.0])
+    };
+    run(&mut s, "solid.press_pull", json!({"face": on(3.0), "distance": 2}));
+    assert!(rel(shape(&mut s, "Block").volume, 24000.0 - corner(5.0)) < 1e-4);
+    keeps_shape_through(&mut s, &["in", "cm", "mm"]);
+    // Pulled again in an inch design: 0.1 more is 2.54 mm more.
+    run(&mut s, "document.units", json!({"units": "in"}));
+    run(&mut s, "solid.press_pull", json!({"face": on(5.0), "distance": 0.1}));
+    assert!(rel(shape(&mut s, "Block").volume, 24000.0 - corner(7.54)) < 1e-4, "{:?}", inputs(&s, 1));
+    keeps_shape_through(&mut s, &["mm", "in"]);
+}
+
+/// A diameter that refers to a unit-less parameter is left as typed: the parameter is read in
+/// the design's units, and when they change it keeps the old one written in, so the part keeps
+/// its size as it did before.
+#[test]
+fn a_diameter_from_a_unitless_parameter_is_left_as_typed() {
+    let mut s = Session::default();
+    run(&mut s, "parameters.add", json!({"name": "w", "expression": "20", "unit": ""}));
+    run(&mut s, "solid.sphere", json!({"diameter": "w", "body_name": "Ball"}));
+    assert_eq!(inputs(&s, 0), ["(w) / 2"]);
+    assert!(rel(shape(&mut s, "Ball").volume, 4.0 / 3.0 * PI * 1000.0) < 1e-3);
+    keeps_shape_through(&mut s, &["in", "mm"]);
+}
+
+/// Beside a unit-less expression that is not a bare number, a bare number stays bare, as it
+/// did: the whole expression is read in the design's units.
+#[test]
+fn bare_numbers_beside_a_unitless_expression_stay_bare() {
+    let mut s = Session::default();
+    run(&mut s, "solid.coil", json!({"diameter": 40, "height": 16, "pitch": "2 * 4", "section_size": 4, "body_name": "A"}));
+    assert_eq!(inputs(&s, 0)[2], "(16) / (2 * 4)", "the revolutions");
+    assert!(s.model.result(s.doc.features[0].id).is_some_and(|r| r.error.is_none()));
+    run(&mut s, "solid.box", json!({"length": 20, "width": 10, "height": 10, "center": ["2 * 5", 0, 0], "body_name": "B"}));
+    assert_eq!(s.doc.features[1].kind.point_expr().map(|p| p[0].clone()), Some("(2 * 5) - (20) / 2".to_string()));
+    let b = shape(&mut s, "B");
+    assert!(b.bbox[0].abs() < 1e-6 && (b.bbox[3] - 20.0).abs() < 1e-6, "{b:?}");
+}