testkit: corpus --part NAME --design PATH writes a part's .solidcraft design

Opens a corpus part in the app or over MCP without solidcraft-cli.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

crates/testkit/src/bin/corpus.rs

@@ -1,26 +1,39 @@
 //! `corpus [--part NAME] [--no-write]`: see [`modelcraft_testkit::runner`]; run it as
 //! `cargo xtask corpus`.
+//!
+//! `corpus --part NAME --design PATH` writes that part's `.solidcraft` design to `PATH` instead
+//! (its recipe run, or its shape generated), for opening the part in the app or over MCP.
 #![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
 #![forbid(unsafe_code)]
 
+use std::path::Path;
 use std::process::ExitCode;
 
+const USAGE: &str = "usage: corpus [--part NAME] [--no-write] | corpus --part NAME --design PATH";
+
 fn main() -> ExitCode {
     let args: Vec<String> = std::env::args().skip(1).collect();
     let mut only = None;
+    let mut design = None;
     let mut write = true;
     let mut it = args.iter();
     while let Some(a) = it.next() {
         match a.as_str() {
             "--part" => only = it.next().map(String::as_str),
+            "--design" => design = it.next().map(String::as_str),
             "--no-write" => write = false,
             other => {
-                eprintln!("error: unknown argument `{other}`\nusage: corpus [--part NAME] [--no-write]");
+                eprintln!("error: unknown argument `{other}`\n{USAGE}");
                 return ExitCode::FAILURE;
             }
         }
     }
-    match modelcraft_testkit::runner::run(&modelcraft_testkit::corpus::workspace_root(), only, write) {
+    let result = match (design, only) {
+        (Some(path), Some(name)) => write_design(name, Path::new(path)),
+        (Some(_), None) => Err(format!("--design needs --part\n{USAGE}")),
+        (None, _) => modelcraft_testkit::runner::run(&modelcraft_testkit::corpus::workspace_root(), only, write),
+    };
+    match result {
         Ok(()) => ExitCode::SUCCESS,
         Err(e) => {
             eprintln!("error: {e}");
@@ -28,3 +41,13 @@ fn main() -> ExitCode {
         }
     }
 }
+
+/// Write the design of the corpus part `name` to `path`.
+fn write_design(name: &str, path: &Path) -> Result<(), String> {
+    let parts = modelcraft_testkit::corpus::parts().map_err(|e| e.to_string())?;
+    let part = parts.iter().find(|p| p.name == name).ok_or_else(|| format!("no corpus part named `{name}`"))?;
+    let bytes = modelcraft_testkit::corpus::design_bytes(part).map_err(|e| e.to_string())?;
+    std::fs::write(path, bytes).map_err(|e| format!("{}: {e}", path.display()))?;
+    eprintln!("corpus: wrote {} ({name})", path.display());
+    Ok(())
+}

xtask/src/main.rs

@@ -36,7 +36,8 @@ commands:
                   tests, and the benchmarks) and the doc tests alongside: the CI heavy job
   corpus [--part NAME] [--no-write]
                   build every meshing test corpus part (tests/corpus, analytic shapes), tessellate
-                  and mesh it, and write the results to docs/meshing/corpus.md (release build)
+                  and mesh it, and write the results to docs/meshing/corpus.md (release build);
+                  --part NAME --design PATH writes that part's .solidcraft design instead
   oracle [--case NAME]... [--bless NAME|all]... [--quick] [--no-write]
                   run the verification and validation cases (tests/oracle, docs/verification.md)
                   against their references and fixtures; write docs/oracle.md after a full run;