REPL: dot-commands produce SyntaxError inside multi-line input

從 lib/repl.js 開始，重點關注 Recoverable-error 路徑、kAddNewLineOnTTY 和 onLine(cmd) 處理程序。使用 node -i 和提供的 printf 命令重現問題，然後追蹤緩衝的多行輸入如何到達點命令檢查。完成的標準是：.break、.clear、.exit 和 .help 能在多行輸入中運作，且不會產生 SyntaxError。

Version

any v24.1.0+

Platform

Tested on:
Microsoft Windows NT 10.0.19045.0 x64;
WSL2 Debian;

Subsystem

REPL

What steps will reproduce the bug?

printf "function a() {\n.break\n" | node -i
printf "function a() {\n.exit\n" | node -i
printf "function a() {\n.help\n" | node -i

How often does it reproduce? Is there a required condition?

Always. Required condition: any registered dot-command typed as the first line after a Recoverable error if self.terminal === true. This includes both real interactive TTYs and node -i with piped stdin.

What is the expected behavior? Why is that the expected behavior?

Welcome to Node.js v24.0.2.
Type ".help" for more information.
> function a() {
| .exit

Welcome to Node.js v24.0.2.
Type ".help" for more information.
> function a() {
| .break
>

Welcome to Node.js v24.0.2.
Type ".help" for more information.
> function a() {
| .help
.break    Sometimes you get stuck, this gets you out
.clear    Alias for .break
.editor   Enter editor mode
.exit     Exit the REPL
.help     Print this help message
.load     Load JS from a file into the REPL session
.save     Save all evaluated commands in this REPL session to a file
Press Ctrl+C to abort current expression, Ctrl+D to exit the REPL
|

What do you see instead?

Welcome to Node.js v24.1.0.
Type ".help" for more information.
> function a() {
| .exit
.exit
^
Uncaught SyntaxError: Unexpected token '.'

Welcome to Node.js v24.1.0.
Type ".help" for more information.
> function a() {
| .break
.break
^
Uncaught SyntaxError: Unexpected token '.'

Welcome to Node.js v24.1.0.
Type ".help" for more information.
> function a() {
| .help
.help
^
Uncaught SyntaxError: Unexpected token '.'

Additional information

The expected behavior is dot-commands working in multi-line mode. Since 24.1.0 they do not. Only changes to TTY multi-line input behavior in 24.1.0 were introduced by #58003.
Bisect:

git checkout v24.1.0
./configure
make -j2 node > /dev/null 2>/dev/null 
printf "function a(){\n.break\n" | ./node -i

git checkout 629a954477^
make -j2 node > /dev/null 2>/dev/null
printf "function a(){\n.break\n" | ./node -i

git checkout 629a954477
make -j2 node > /dev/null 2>/dev/null
printf "function a(){\n.break\n" | ./node -i

Hunk level bisect:

git checkout 629a954477
make -j2 node >/dev/null 2>/dev/null

printf "n\nn\nn\nn\ny\nn\n" | git checkout -p 629a954477^ -- lib/repl.js
make -j2 node >/dev/null 2>/dev/null
printf "function a() {\n.break\n" | ./node -i

particular hunk introducing the bug:

@@ -943,33 +941,15 @@ function REPLServer(prompt,
       }

       // If error was SyntaxError and not JSON.parse error
-      if (e) {
-        if (e instanceof Recoverable && !sawCtrlD) {
-          // Start buffering data like that:
-          // {
-          // ...  x: 1
-          // ... }
+      // We can start a multiline command
+      if (e instanceof Recoverable && !sawCtrlD) {
+        if (self.terminal) {
+          self[kAddNewLineOnTTY]();
+        } else {
           self[kBufferedCommandSymbol] += cmd + '\n';
           self.displayPrompt();
-          return;
-        }
-      }
-
-      // In the next two if blocks, we do not use os.EOL instead of '\n'
-      // because on Windows it is '\r\n'
-      if (StringPrototypeIncludes(cmd, '\n')) { // If you are editing a multiline command
-        self.history[0] = self[kNormalizeHistoryLineEndings](cmd, '\n', '\r');
-      } else if (self[kBufferedCommandSymbol]) { // If a new multiline command was entered
-        // Remove the first N lines from the self.history array
-        // where N is the number of lines in the buffered command
-
-        const lines = StringPrototypeSplit(self[kBufferedCommandSymbol], '\n');
-        self.history = ArrayPrototypeSlice(self.history, lines.length);
-        lines[lines.length - 1] = cmd;
-        const newHistoryLine = ArrayPrototypeJoin(ArrayPrototypeReverse(lines), '\r');
-        if (self.history[0] !== newHistoryLine) {
-          ArrayPrototypeUnshift(self.history, newHistoryLine);
         }
+        return;
       }

       if (e) {

Reason:

1. The change in handling of Recoverable error shifts the TTY multi-line handling into self[kAddNewLineOnTTY]();.
2. It causes onLine(cmd) handler to be called with the whole multi-line buffer in cmd.
3. That results in the REPL keyword check failing - instead of checking the first character in ".break" it checks the first character in "function a() {\r.break". (\n becomes \r in kAddHistory, not relevant to the bug)
4. Which leads to REPL keywords being passed to eval where they produce SyntaxError: Unexpected token '.'.