`node:readline` fails to correctly handle Ctrl+D signals, `rl.on('close')` and `completer` tab completions

[jhmaster2000]

What version of Bun is running?

0.6.3

What platform is your computer?

Linux 5.15.90.1-microsoft-standard-WSL2 x86_64 x86_64

What steps can reproduce the bug?

There are multiple issues with the readline polyfill at the moment, given the following sample file test.ts:

import readline from 'readline/promises';
const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    terminal: true,
    tabSize: 4,
    prompt: '> ',
    historySize: 10,
    history: ['test history 1', 'test history 2', 'test history 3', 'test history 4', 'test history 5'],
    completer(line: string) {
        const completions = ['hello', 'world'];
        const hits = completions.filter(c => c.startsWith(line));
        return [hits.length ? hits : completions, line];
    }
});
rl.prompt();
rl.on('line', (line: string) => {
    console.log(`Line: ${line}`);
    rl.prompt();
});
rl.on('close', () => {
    console.log('Exiting...');
    process.exit(0);
});

Ran on Bun with: bun run test.ts Ran on Node.js for comparison with: ts-node-esm test.ts (npm i -g ts-node)

What is the expected behavior?

Running the file in Node.js as indicated above and performing the following sequence of inputs:

1. Press Arrow Up 3 times (it should cycle through the preset history from test history 1 to test history 3 on the prompt)
2. Press Enter (it should print Line: test history 3)
3. Type "sample text" into the prompt and press Enter (it should print Line: sample text)
4. Press Arrow Up (it should show sample text from the updated history)
5. Press Arrow Down (it should go back to the blank prompt)
6. Type h and press Tab (it should auto-complete to hello) then press Enter (it should print Line: hello)
7. Type w and press Tab (it should auto-complete to world) then press Tab again (it should list matching completions)
8. Press Enter (it should print Line: world)
9. Press Tab twice (it should print all completions hello world
10. Press Ctrl + D to exit (It should print Exiting... and then terminate the program)

    Resulting in the below final output:

    
    > test history 3
    Line: test history 3
    > sample text
    Line: sample text
    > hello
    Line: hello
    > world
    world

world Line: world

hello world

Exiting...

What do you see instead?

Running the same file in Bun following the same inputs as above:

Results in the following output: (this output is outdated and no longer relevant)

> ^[[A^[[A^[[A
687 |       // Parse the key modifier
688 |       keyCtrl = !!(modifier & 4);
689 |       keyMeta = !!(modifier & 10);
690 |       keyShift = !!(modifier & 1);
691 | 
692 |       keyCode = code;
         ^
ReferenceError: Can't find variable: keyCode
      at node:readline:692:6
      at onData (node:readline:1192:12)
      at addChunk (node:stream:2713:8)
      at readableAddChunk (node:stream:2694:12)
sample text
sample text
Line: sample text
> ^[[A^[[Bh
687 |       // Parse the key modifier
688 |       keyCtrl = !!(modifier & 4);
689 |       keyMeta = !!(modifier & 10);
690 |       keyShift = !!(modifier & 1);
691 | 
692 |       keyCode = code;
         ^
ReferenceError: Can't find variable: keyCode
      at node:readline:692:6
      at onData (node:readline:1192:12)
      at addChunk (node:stream:2713:8)
      at readableAddChunk (node:stream:2694:12)
w
w
Line: w
>                       1918 |     this[kBeforeEdit](this.line, this.cursor);
1919 | 
1920 |     // Apply/show completions.
1921 |     var completionsWidth = ArrayPrototypeMap.call(completions, e => getStringWidth(e));
1922 | 
1923 |     var width = MathMaxApply(completionsWidth) + 2; // 2 space padding
                   ^
TypeError: undefined is not a function
      at [_tabCompleter] (node:readline:1923:16)
      at node:readline:1890:4
^C

Going over everything that went wrong here:

Striked out issues have been fixed.

Issue at steps 1, 2, 4, 5, 6:

• Has already been reported at #2035 so I will not focus on it, this issue is for the other issues not covered by the linked issue.

Issue at steps 3 & 8:

• The input texts (sample text and w respectively) have been duplicated. This only occurs if an error has happened in the previous prompt.

Issue at steps 7 & 9: (Remains in Bun 0.8.2)

• Pressing Tab simply enters an actual tab into the input, rather than triggering completions.
• Same goes for double Tab
• When enter is pressed with a Tab character in the prompt, it sometimes triggers the error seen under Line: w
  • This error is sadly not consistent for some reason.

Issue at step 10:

• Ctrl + D will make the program unresponsive to the terminal, but it will not terminate.
• Ctrl + C is required to terminate.
• Exiting... was not printed. rl.on("close") was not called.

Bonus Issue

• On step 6, after pressing Tab but before pressing Enter, hold down Backspace
• You would expect to be able to wipe the line clean back to blank.
• Instead, the first character of the prompt (^ in this case) becomes undeletable.
• The character is a ghost character, since the 'line' event doesn't echo it back when pressing Enter.
• This isn't necessarily always the first character of the prompt, more generally, backspace behaves weirdly after tabbing.

Additional information

Updated for Bun v0.6.3 (issue persists)

[birkskyum]

What I experience here is that some keys get typed double. This appear similar to:

• https://github.com/oven-sh/bun/issues/3099

[birkskyum]

Update with Canary after #3099 was fixed. In step 7 it still breaks for me, because it seems like Tab is clicked twice even though I'm sure I only click it one. The result is that w "Tab+Tab" gives:

> worldLine: world
> Exiting...

So I can't get beyond step 7 due to this.

[birkskyum]

@dylan-conway , after looking at the clack issue, do you have any idea why "Tab" might be executed twice?

[birkskyum]

The issue with double letters met when writing "sample text" and the issue with Ctrl+D to exit appear to have been resolved

[dylan-conway]

@dylan-conway , after looking at the clack issue, do you have any idea why "Tab" might be executed twice?

I'm not sure yet, I tried to fix this yesterday but failed. I'll try again today. Seems to be related to the readline exit event

[jhmaster2000]

On current 0.8.2 canary on Linux all the issues are resolved for me, except for completions which hitting Tab makes the entire stdin freeze and become completely unresponsive.

Without a completer function specified Tab behaves normally, so at least readline is now usable without completions.

[Subwaytime]

Seems to relate to my issue as well: #4835

[Electroid]

In Bun v1.0.7, it appears to exit after you get to the w step and press Tab.

❯ bun rl.ts
> test history 3
Line: test history 3
> sample text
Line: sample text
> sample text
Line: sample text
> hello
Line: hello
> worldLine: world
> Exiting...

[jhmaster2000]

Yep, can reproduce, to put it in general terms, it seems to succeed at a first completion and then crashes on a second one, likely something not being properly cleaned up/freed for re-use in the completion handling code.

[paperdave]

👀 i think i fixed this