fix(desktop): find spawn-helper in universal macOS builds (#1630)

The universal build ships app-arm64.asar and app-x64.asar instead of
app.asar, so node-pty's helper path rewrite never pointed at the
unpacked copy and every local terminal failed with posix_spawnp failed.

src/backend/tests/electron/local-shell.test.ts

@@ -80,4 +80,20 @@ describe("repairSpawnHelpers", () => {
     expect(chmods[0][1] & 0o111).not.toBe(0);
     expect(chmods[0][0]).toContain("app.asar.unpacked");
   });
+
+  it.each(["app-arm64.asar", "app-x64.asar"])(
+    "repairs the helper in the unpacked copy of a universal build's %s",
+    (asar) => {
+      const chmods: string[] = [];
+      const fsImpl = {
+        statSync: () => ({ mode: 0o644 }),
+        chmodSync: (file: string) => {
+          chmods.push(file.split(require("node:path").sep).join("/"));
+        },
+      };
+      const dir = `/Applications/Termix.app/Contents/Resources/${asar}/node_modules/node-pty`;
+      repairSpawnHelpers(dir, fsImpl);
+      expect(chmods[0]).toContain(`/${asar}.unpacked/node_modules/node-pty/`);
+    },
+  );
 });

src/backend/tests/electron/patch-node-pty.test.ts

@@ -11,7 +11,48 @@ import { tmpdir } from "node:os";
 import { describe, expect, it } from "vitest";
 
 const require = createRequire(import.meta.url);
-const { chmodSpawnHelpers } = require("../../../../scripts/patch-node-pty.cjs");
+const {
+  chmodSpawnHelpers,
+  patchUnixTerminalHelperRewrite,
+} = require("../../../../scripts/patch-node-pty.cjs");
+
+const upstreamRewrite = [
+  "helperPath = helperPath.replace('app.asar', 'app.asar.unpacked');",
+  "helperPath = helperPath.replace('node_modules.asar', 'node_modules.asar.unpacked');",
+].join("\n");
+
+const previouslyPatchedRewrite = [
+  "if (!helperPath.includes('app.asar.unpacked')) {",
+  "    helperPath = helperPath.replace('app.asar', 'app.asar.unpacked');",
+  "}",
+  "if (!helperPath.includes('node_modules.asar.unpacked')) {",
+  "    helperPath = helperPath.replace('node_modules.asar', 'node_modules.asar.unpacked');",
+  "}",
+].join("\n");
+
+const resources = "/Applications/Termix.app/Contents/Resources";
+const helperPaths = [
+  ["app.asar", "app.asar.unpacked"],
+  ["app-arm64.asar", "app-arm64.asar.unpacked"],
+  ["app-x64.asar", "app-x64.asar.unpacked"],
+  ["app.asar.unpacked", "app.asar.unpacked"],
+  ["app-arm64.asar.unpacked", "app-arm64.asar.unpacked"],
+].map(([from, to]) => [
+  `${resources}/${from}/node_modules/node-pty/build/Release/spawn-helper`,
+  `${resources}/${to}/node_modules/node-pty/build/Release/spawn-helper`,
+]);
+
+function writeUnixTerminal(rewrite: string) {
+  const file = join(
+    tmpdir(),
+    `termix-unix-terminal-${Date.now()}-${Math.random()}.cjs`,
+  );
+  writeFileSync(
+    file,
+    `module.exports = function (helperPath) {\n${rewrite}\nreturn helperPath;\n};\n`,
+  );
+  return file;
+}
 
 // chmod's execute bit is a POSIX concept; Windows/NTFS has no equivalent mode bit.
 const itPosix = process.platform === "win32" ? it.skip : it;
@@ -30,4 +71,22 @@ describe("patch-node-pty", () => {
     expect(chmodSpawnHelpers(root)).toBe(0);
     expect(existsSync(helper)).toBe(true);
   });
+
+  it.each([
+    ["upstream", upstreamRewrite],
+    ["previously patched", previouslyPatchedRewrite],
+  ])(
+    "points the %s helper path at the unpacked copy of any app asar",
+    (_, rewrite) => {
+      const file = writeUnixTerminal(rewrite);
+
+      expect(patchUnixTerminalHelperRewrite(file)).toBe(true);
+      expect(patchUnixTerminalHelperRewrite(file)).toBe(false);
+
+      const rewriteHelperPath = require(file);
+      for (const [from, to] of helperPaths) {
+        expect(rewriteHelperPath(from)).toBe(to);
+      }
+    },
+  );
 });