src: add --no-restore-terminal-state

doc/api/cli.md

@@ -2435,6 +2435,26 @@ Disable support for loading a synchronous ES module graph in `require()`.
 
 See [Loading ECMAScript modules using `require()`][].
 
+### `--no-restore-terminal-state`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+On POSIX systems, disable restoration of the terminal settings captured at startup
+when the process exits. These settings are restored by default.
+This option can be useful when piping output to an interactive pager that changes
+the same terminal's settings:
+
+```bash
+node --no-restore-terminal-state --help | less
+```
+
+This option does not disable libuv's terminal mode cleanup or restoration of the
+`O_NONBLOCK` flag on standard I/O file descriptors. Applications using this option
+must restore terminal settings not restored by libuv, including changes made
+through native addons or child processes. It has no effect on Windows.
+
 ### `--no-strip-types`
 
 <!-- YAML
@@ -4302,6 +4322,7 @@ one is included in the list below.
 * `--no-force-async-hooks-checks`
 * `--no-global-search-paths`
 * `--no-network-family-autoselection`
+* `--no-restore-terminal-state`
 * `--no-strip-types`
 * `--no-warnings`
 * `--no-webstorage`

doc/node.1

@@ -1245,6 +1245,19 @@ enables it.
 Disable support for loading a synchronous ES module graph in \fBrequire()\fR.
 See Loading ECMAScript modules using \fBrequire()\fR.
 .
+.It Fl -no-restore-terminal-state
+On POSIX systems, disable restoration of the terminal settings captured at startup
+when the process exits. These settings are restored by default.
+This option can be useful when piping output to an interactive pager that changes
+the same terminal's settings:
+.Bd -literal
+node --no-restore-terminal-state --help | less
+.Ed
+This option does not disable libuv's terminal mode cleanup or restoration of the
+\fBO_NONBLOCK\fR flag on standard I/O file descriptors. Applications using this option
+must restore terminal settings not restored by libuv, including changes made
+through native addons or child processes. It has no effect on Windows.
+.
 .It Fl -no-strip-types
 Disable type-stripping for TypeScript files.
 For more information, see the TypeScript type-stripping documentation.
@@ -2341,6 +2354,8 @@ one is included in the list below.
 .It
 \fB--no-network-family-autoselection\fR
 .It
+\fB--no-restore-terminal-state\fR
+.It
 \fB--no-strip-types\fR
 .It
 \fB--no-warnings\fR

src/node.cc

@@ -533,14 +533,16 @@ void ResetSignalHandlers() {
 // variable on all platforms that we support, which we require in
 // order for its value to be usable inside signal handlers.
 static std::atomic<uint32_t> init_process_flags = 0;
+static std::atomic<uint32_t> restore_terminal_state = 1;
 static_assert(
     std::is_same_v<std::underlying_type_t<ProcessInitializationFlags::Flags>,
                    uint32_t>);
 
 static void PlatformInit(ProcessInitializationFlags::Flags flags) {
-  // init_process_flags is accessed in ResetStdio(),
+  // These atomics are accessed in ResetStdio(),
   // which can be called from signal handlers.
   CHECK(init_process_flags.is_lock_free());
+  CHECK(restore_terminal_state.is_lock_free());
   init_process_flags.store(flags);
 
   if (!(flags & ProcessInitializationFlags::kNoStdioInitialization)) {
@@ -707,7 +709,7 @@ void ResetStdio() {
       CHECK_NE(err, -1);
     }
 
-    if (s.isatty) {
+    if (s.isatty && restore_terminal_state.load()) {
       sigset_t sa;
       int err;
 
@@ -1261,6 +1263,10 @@ InitializeOncePerProcessInternal(
   {
     result->exit_code_ = InitializeNodeWithArgsInternal(
         &result->args_, &result->exec_args_, &result->errors_, flags);
+    // cli_options is not safe to access from the signal handlers that call
+    // ResetStdio().
+    restore_terminal_state.store(
+        per_process::cli_options->restore_terminal_state);
     if (result->exit_code_enum() != ExitCode::kNoFailure) {
       result->early_return_ = true;
       return result;

src/node_options.cc

@@ -1636,6 +1636,11 @@ PerProcessOptionsParser::PerProcessOptionsParser(
             "automatically zero-fill all newly allocated Buffer instances",
             BOOL_FIELD(zero_fill_all_buffers),
             kAllowedInEnvvar);
+  AddOption("--restore-terminal-state",
+            "disable restoration of startup terminal settings",
+            BOOL_FIELD(restore_terminal_state),
+            kAllowedInEnvvar,
+            true);
   AddOption("--debug-arraybuffer-allocations",
             "", /* undocumented, only for debugging */
             BOOL_FIELD(debug_arraybuffer_allocations),

src/node_options.h

@@ -417,6 +417,7 @@ class PerProcessOptions : public Options {
 
   DEFINE_BOOL_FIELD(zero_fill_all_buffers) = false;
   DEFINE_BOOL_FIELD(debug_arraybuffer_allocations) = false;
+  DEFINE_BOOL_FIELD(restore_terminal_state) = true;
 
   // We enable the shared read-only heap which currently requires that the
   // snapshot used in different isolates in the same process to be the same.

test/pseudo-tty/test-tty-restore-terminal-state.js

@@ -0,0 +1,86 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const { spawn } = require('child_process');
+const { once } = require('events');
+const { spawnSyncAndExitWithoutError } = require('../common/child_process');
+
+// Refs: https://github.com/nodejs/node/issues/66440
+
+function stty(args) {
+  const { child: { stdout } } = spawnSyncAndExitWithoutError('stty', args, {
+    encoding: 'utf8',
+    stdio: ['inherit', 'pipe', 'inherit'],
+  });
+  return stdout.trim();
+}
+
+const childScript = [
+  'process.channel.ref();',
+  'process.once("message", (exit) => {',
+  '  process.disconnect();',
+  '  if (exit === "process.exit") process.exit(0);',
+  '});',
+  'process.send("ready");',
+].join('\n');
+
+const rawChildScript = `process.stdin.setRawMode(true);\n${childScript}`;
+
+async function checkExit(exit, args, nodeOptions, restore, script = childScript) {
+  const initialFlags = stty(['-a']);
+  assert.match(initialFlags, /(?:^|[\s;])icanon(?:[\s;]|$)/);
+  assert.match(initialFlags, /(?:^|[\s;])echo(?:[\s;]|$)/);
+
+  const child = spawn(process.execPath, [...args, '-e', script], {
+    env: { ...process.env, NODE_OPTIONS: nodeOptions },
+    stdio: ['inherit', 'pipe', 'inherit', 'ipc'],
+  });
+  const exited = once(child, 'exit');
+
+  try {
+    // The child must capture the startup settings before stty changes them.
+    const [message] = await Promise.race([once(child, 'message'), exited]);
+    assert.strictEqual(message, 'ready');
+    stty(['-echo']);
+    const changedFlags = stty(['-a']);
+    assert.match(changedFlags, /(?:^|[\s;])-echo(?:[\s;]|$)/);
+
+    if (exit === 'SIGINT') {
+      assert.strictEqual(child.kill('SIGINT'), true);
+    } else {
+      child.send(exit);
+    }
+
+    const [code, signal] = await exited;
+    assert.strictEqual(code, exit === 'SIGINT' ? null : 0);
+    assert.strictEqual(signal, exit === 'SIGINT' ? 'SIGINT' : null);
+    const finalFlags = stty(['-a']);
+    assert.match(finalFlags, /(?:^|[\s;])icanon(?:[\s;]|$)/, exit);
+    assert.strictEqual(/(?:^|[\s;])echo(?:[\s;]|$)/.test(finalFlags), restore, exit);
+  } finally {
+    try {
+      if (child.exitCode === null && child.signalCode === null) {
+        child.kill('SIGKILL');
+        await exited;
+      }
+    } finally {
+      stty(['echo']);
+    }
+  }
+}
+
+async function main() {
+  for (const exit of ['natural', 'process.exit', 'SIGINT']) {
+    await checkExit(exit, ['--no-restore-terminal-state'], '', false);
+    await checkExit(exit, [], '', true);
+    await checkExit(exit, ['--no-restore-terminal-state'], '', true, rawChildScript);
+  }
+  if (!process.config.variables.node_without_node_options) {
+    await checkExit('natural', [], '--no-restore-terminal-state', false);
+    await checkExit('natural', ['--restore-terminal-state'],
+                    '--no-restore-terminal-state', true);
+  }
+}
+
+main().then(common.mustCall());