fix: start the macOS local terminal when the shell or spawn helper is broken (Support#1418)

electron/local-shell.cjs

@@ -1,4 +1,16 @@
-function resolveLocalShell(platform, requestedShell, env = process.env) {
+const fs = require("node:fs");
+const path = require("node:path");
+
+function isUsableShell(file, exists) {
+  return !!file && (!path.isAbsolute(file) || exists(file));
+}
+
+function resolveLocalShell(
+  platform,
+  requestedShell,
+  env = process.env,
+  exists = fs.existsSync,
+) {
   if (platform === "win32") {
     if (requestedShell === "wsl") {
       return { file: "wsl.exe", args: [] };
@@ -9,13 +21,47 @@ function resolveLocalShell(platform, requestedShell, env = process.env) {
     };
   }
 
-  return {
-    file:
-      env.TERMIX_LOCAL_SHELL ||
-      env.SHELL ||
-      (platform === "darwin" ? "/bin/zsh" : "/bin/bash"),
-    args: ["-l"],
-  };
+  // A SHELL left pointing at an uninstalled shell makes the spawn fail.
+  const fallbacks =
+    platform === "darwin"
+      ? ["/bin/zsh", "/bin/bash", "/bin/sh"]
+      : ["/bin/bash", "/bin/sh"];
+  const file =
+    [env.TERMIX_LOCAL_SHELL, env.SHELL, ...fallbacks].find((candidate) =>
+      isUsableShell(candidate, exists),
+    ) || fallbacks[0];
+  return { file, args: ["-l"] };
 }
 
-module.exports = { resolveLocalShell };
+/**
+ * node-pty starts every shell through its spawn-helper binary, and a packaged
+ * copy that lost its execute bit fails with "posix_spawnp failed". Returns
+ * how many helpers were fixed.
+ */
+function repairSpawnHelpers(ptyDir, fsImpl = fs) {
+  const dir = ptyDir.replace(/app\.asar(?!\.unpacked)/, "app.asar.unpacked");
+  const candidates = [
+    path.join(dir, "build", "Release", "spawn-helper"),
+    path.join(
+      dir,
+      "prebuilds",
+      `${process.platform}-${process.arch}`,
+      "spawn-helper",
+    ),
+  ];
+  let fixed = 0;
+  for (const helper of candidates) {
+    try {
+      const mode = fsImpl.statSync(helper).mode;
+      if ((mode & 0o111) === 0) {
+        fsImpl.chmodSync(helper, mode | 0o755);
+        fixed += 1;
+      }
+    } catch {
+      // Missing or read-only; nothing to fix here.
+    }
+  }
+  return fixed;
+}
+
+module.exports = { resolveLocalShell, repairSpawnHelpers };

electron/main.cjs

@@ -33,7 +33,7 @@ const { launchNativeRdp } = require("./native-rdp.cjs");
 const { isCloseActiveTabInput } = require("./keyboard-shortcuts.cjs");
 const { quitApp } = require("./app-quit.cjs");
 const { selectLinuxPasswordStore } = require("./linux-password-store.cjs");
-const { resolveLocalShell } = require("./local-shell.cjs");
+const { resolveLocalShell, repairSpawnHelpers } = require("./local-shell.cjs");
 const { registerLocalFileHandlers } = require("./local-files.cjs");
 
 const localTerminalSessions = new Map();
@@ -3240,17 +3240,32 @@ ipcMain.handle("local-terminal-start", (event, dimensions = {}) => {
   const rows = Math.min(300, Math.max(1, Number(dimensions.rows) || 24));
   const sessionId = crypto.randomUUID();
   const shellConfig = resolveLocalShell(process.platform, dimensions.shell);
-  const child = pty.spawn(shellConfig.file, shellConfig.args, {
-    name: "xterm-256color",
-    cols,
-    rows,
-    cwd: os.homedir(),
-    env: {
-      ...process.env,
-      TERM: "xterm-256color",
-      COLORTERM: "truecolor",
-    },
-  });
+  const spawnShell = () =>
+    pty.spawn(shellConfig.file, shellConfig.args, {
+      name: "xterm-256color",
+      cols,
+      rows,
+      cwd: os.homedir(),
+      env: {
+        ...process.env,
+        TERM: "xterm-256color",
+        COLORTERM: "truecolor",
+      },
+    });
+  let child;
+  try {
+    child = spawnShell();
+  } catch (error) {
+    const ptyDir = path.dirname(require.resolve("node-pty/package.json"));
+    if (
+      !String(error?.message).includes("posix_spawnp") ||
+      repairSpawnHelpers(ptyDir) === 0
+    ) {
+      throw error;
+    }
+    logToFile("[local-terminal] restored the spawn-helper execute bit");
+    child = spawnShell();
+  }
   const ownerId = event.sender.id;
   const session = { ownerId, process: child, ready: false, buffered: "" };
   localTerminalSessions.set(sessionId, session);

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

@@ -2,13 +2,21 @@ import { createRequire } from "node:module";
 import { describe, expect, it } from "vitest";
 
 const require = createRequire(import.meta.url);
-const { resolveLocalShell } =
+const { resolveLocalShell, repairSpawnHelpers } =
   require("../../../../electron/local-shell.cjs") as {
     resolveLocalShell: (
       platform: NodeJS.Platform,
       requestedShell?: string,
       env?: NodeJS.ProcessEnv,
+      exists?: (file: string) => boolean,
     ) => { file: string; args: string[] };
+    repairSpawnHelpers: (
+      ptyDir: string,
+      fsImpl: {
+        statSync: (file: string) => { mode: number };
+        chmodSync: (file: string, mode: number) => void;
+      },
+    ) => number;
   };
 
 describe("resolveLocalShell", () => {
@@ -27,9 +35,49 @@ describe("resolveLocalShell", () => {
   });
 
   it("preserves the configured shell on non-Windows platforms", () => {
-    expect(resolveLocalShell("linux", "wsl", { SHELL: "/bin/fish" })).toEqual({
+    expect(
+      resolveLocalShell("linux", "wsl", { SHELL: "/bin/fish" }, () => true),
+    ).toEqual({
       file: "/bin/fish",
       args: ["-l"],
     });
   });
+
+  it("skips a configured shell that is not installed", () => {
+    const installed = new Set(["/bin/bash", "/bin/zsh"]);
+    expect(
+      resolveLocalShell(
+        "darwin",
+        undefined,
+        { SHELL: "/opt/homebrew/bin/fish" },
+        (file) => installed.has(file),
+      ).file,
+    ).toBe("/bin/zsh");
+  });
+});
+
+describe("repairSpawnHelpers", () => {
+  it("restores the execute bit in the unpacked copy only when it is missing", () => {
+    const modes = new Map<string, number>();
+    const chmods: Array<[string, number]> = [];
+    const fsImpl = {
+      statSync: (file: string) => {
+        const mode = modes.get(file);
+        if (mode === undefined) throw new Error("ENOENT");
+        return { mode };
+      },
+      chmodSync: (file: string, mode: number) => {
+        chmods.push([file, mode]);
+      },
+    };
+    const dir =
+      "/Applications/Termix.app/Contents/Resources/app.asar/node_modules/node-pty";
+    const unpacked = dir.replace("app.asar", "app.asar.unpacked");
+    const release = `${unpacked}/build/Release/spawn-helper`;
+    modes.set(release.split("/").join(require("node:path").sep), 0o644);
+    modes.set(release, 0o644);
+    expect(repairSpawnHelpers(dir, fsImpl)).toBe(1);
+    expect(chmods[0][1] & 0o111).not.toBe(0);
+    expect(chmods[0][0]).toContain("app.asar.unpacked");
+  });
 });