Sheet metal: an Edge Flange can choose its own corner relief (#1481)

An Edge Flange feature can set the shape and size of the relief at the corners its flanges make, in place of the sheet metal rule's. Design format 24.

Co-authored-by: NOWN-DEV <NOWN-DEV@users.noreply.github.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

crates/doc/src/format.rs

@@ -233,13 +233,18 @@
 //!   read through cadmpeg); its `step` is still the STEP text the file was restated as, so the
 //!   feature's fields are unchanged and version 22 designs need no transformation; 0.13.x asks
 //!   for an update before it meets these imports.
+//! - 24: an Edge Flange feature can choose its own corner relief (`corner_relief_shape`: notch,
+//!   round, rectangular or tear, and `corner_relief`, the size across), for the corners its
+//!   flanges make. Version 23 designs need no transformation: a feature without them follows the
+//!   sheet metal rule, as it always did, and saves as before; 0.13.0 (which reads up to 22) asks
+//!   for an update instead of silently building the rule's relief where a design asks for another.
 
 use serde_json::Value;
 
 use crate::{DocError, Document, Result};
 
 /// The format this build writes.
-pub const FORMAT: u32 = 23;
+pub const FORMAT: u32 = 24;
 
 pub fn format_string(n: u32) -> String {
     format!("solidcraft/{n}")
@@ -256,7 +261,7 @@ pub fn version_of(s: &str) -> Option<u32> {
 
 /// JSON-level upgrades: entry `i` turns format `i + 1` into `i + 2`.
 type JsonStep = fn(&mut Value) -> Result<()>;
-const JSON_STEPS: [JsonStep; 22] = [
+const JSON_STEPS: [JsonStep; 23] = [
     |_| Ok(()),
     v2_to_v3,
     v3_to_v4,
@@ -279,6 +284,7 @@ const JSON_STEPS: [JsonStep; 22] = [
     |_| Ok(()),
     |_| Ok(()),
     |_| Ok(()),
+    |_| Ok(()),
 ];
 
 /// Stored face and edge names were worked out from geometry before format 14; they get the
@@ -1011,6 +1017,45 @@ fn normalise(d: &mut Document) -> Result<()> {
 mod tests {
     use super::*;
 
+    /// 24 added the corner relief of an edge flange: a no-op step carries a 23 design up, a flange
+    /// without a relief of its own saves as before, and one with it is saved under 24 and kept.
+    #[test]
+    fn version_twenty_three_designs_open_and_an_edge_flange_relief_is_saved_in_twenty_four() {
+        assert_eq!(JSON_STEPS.len(), FORMAT as usize - 1, "one upgrade step for each format");
+        let flange = |shape: Option<&str>, size: Option<&str>| crate::FeatureKind::SheetFlange {
+            edges: vec![crate::FlangeEdge::at(solidcraft_geom::Vec3::ZERO)],
+            height: "10 mm".into(),
+            angle: "90 deg".into(),
+            radius: None,
+            position: "inside".into(),
+            flip: false,
+            body: None,
+            corner_relief_shape: shape.map(Into::into),
+            corner_relief: size.map(Into::into),
+        };
+        let saved = |document: &Document| -> Value { serde_json::from_str(&document.to_json()).unwrap() };
+        // A flange that follows the rule saves neither key, and a design of format 23 opens as it was.
+        let mut plain = Document::new("A");
+        plain.add_feature(flange(None, None), None).unwrap();
+        let mut file = saved(&plain);
+        let feature = file["features"].as_array().and_then(|f| f.last()).cloned().unwrap();
+        assert_eq!(feature["type"], "sheet_flange");
+        assert!(feature.get("corner_relief_shape").is_none() && feature.get("corner_relief").is_none(), "{feature}");
+        file["format"] = Value::from("solidcraft/23");
+        let opened = read(&file.to_string()).unwrap();
+        assert_eq!(opened.format, format_string(FORMAT));
+        assert_eq!(opened.features, plain.features);
+        // One that chooses its relief says so in the file, which is stamped 24 and keeps it.
+        let mut own = Document::new("A");
+        own.add_feature(flange(Some("round"), Some("6 mm")), None).unwrap();
+        let file = saved(&own);
+        let feature = file["features"].as_array().and_then(|f| f.last()).cloned().unwrap();
+        assert_eq!((&feature["corner_relief_shape"], &feature["corner_relief"]), (&Value::from("round"), &Value::from("6 mm")));
+        // A build that reads up to 23 asks for an update on that stamp instead of dropping the relief.
+        assert_eq!(version_of(file["format"].as_str().unwrap_or_default()), Some(FORMAT));
+        assert_eq!(read(&file.to_string()).unwrap(), own);
+    }
+
     #[test]
     fn version_thirteen_names_keep_their_meaning_under_the_legacy_mark() {
         let file = serde_json::json!({