Clear stale toolpaths on program replacement

web/worker/sim-session.mjs

@@ -1926,6 +1926,11 @@ export class SimSession {
       case "PROGRAM_LOAD": {
         if (["RUNNING", "PAUSED"].includes(this.task.state.state)) return finish(this.error(input, "task_state", "program_load_while_active"), "failed");
         const source = input.payload?.source ?? input.payload?.text ?? input.payload?.program_source;
+        // PROGRAM_LOAD is a replacement transaction. Clear the previous
+        // canonical preview before asking the WASM interpreter to parse the
+        // new source, so a parse/subroutine error cannot re-publish the old
+        // toolpath as if it belonged to the requested file.
+        this.previewState = null;
         if (this.xyzacProgram) {
           this.pendingXyzacMotion = null;
           this.pendingProgramControl = 0;

web/worker/test_xyzac_program_replace.mjs

@@ -0,0 +1,39 @@
+import assert from "node:assert/strict";
+import { readFile } from "node:fs/promises";
+import createModule from "../../build-wasm/linuxcnc-sim-core.js";
+import { loadSimulationCase, toWorkerConfiguration } from "../workspace/sim-case-loader.mjs";
+import { SimSession, CONTEXT_ID } from "./sim-session.mjs";
+
+const CASE = "linuxcnc/configs/sim/axis/vismach/5axis/table-rotary-tilting/xyzac-trt.ini";
+const fetchImpl = async (url) => {
+  try { const body = await readFile(new URL(`../../${String(url).replace(/^\//, "")}`, import.meta.url)); return { ok: true, text: async () => body.toString("utf8") }; }
+  catch { return { ok: false, text: async () => "" }; }
+};
+const bundle = await loadSimulationCase({ path: CASE, fetchImpl });
+const core = await createModule({ wasmBinary: await readFile(new URL("../../build-wasm/linuxcnc-sim-core.wasm", import.meta.url)) });
+const session = new SimSession(core, { sessionId: "xyzac-program-replace" });
+const base = { schema_version: 1, context_id: CONTEXT_ID, session_id: session.sessionId };
+let seq = 0;
+const send = (kind, payload = {}) => session.accept({ ...base, kind, seq: ++seq, operation_id: `replace-${seq}`, payload });
+send("HELLO"); send("SESSION_ATTACH");
+assert.equal(send("LOAD_WORKSPACE", { root_path: "/workspace", configuration: toWorkerConfiguration(bundle) }).payload.status, "verified");
+const first = send("PROGRAM_LOAD", { path: "first.ngc", source: "G21\nG1 X10 Y5 Z2 F100\nM2\n" });
+assert.equal(first.payload.preview.segments.length, 1);
+assert.equal(first.payload.panel_snapshot.visual.toolpath.length, 1);
+const failed = send("PROGRAM_LOAD", { path: "invalid.ngc", source: "G999\n" });
+assert.equal(failed.kind, "ERROR");
+assert.equal(failed.payload.panel_snapshot.visual.toolpath.length, 0);
+assert.equal(session.previewState, null);
+const second = send("PROGRAM_LOAD", { path: "second.ngc", source: "G21\nG1 X1 Y2 Z3 F100\nM2\n" });
+assert.equal(second.payload.program.path, "second.ngc");
+assert.notEqual(second.payload.program.source_hash, first.payload.program.source_hash);
+assert.equal(second.payload.panel_snapshot.visual.toolpath.length, 1);
+
+console.log(JSON.stringify({
+  schema: "xyzac-program-replacement.v1",
+  status: "verified",
+  first_segments: first.payload.panel_snapshot.visual.toolpath.length,
+  failed_segments: failed.payload.panel_snapshot.visual.toolpath.length,
+  second_segments: second.payload.panel_snapshot.visual.toolpath.length,
+  old_preview_retained_after_failure: false,
+}));