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readline: key interval delay for \r & \n #8109

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Checklist
  • make -j4 test (UNIX), or vcbuild test nosign (Windows) passes
  • tests and/or benchmarks are included
  • commit message follows commit guidelines
Affected core subsystem(s)

readline

Description of change

Emit two line events when there is a delay between
CR('\r') and LF('\n')

@nodejs-github-bot nodejs-github-bot added the readline Issues and PRs related to the built-in readline module. label Aug 15, 2016
@@ -199,6 +199,27 @@ function isWarned(emitter) {
assert.equal(callCount, expectedLines.length);
rli.close();

// Emit two line events where there is a delay
// between \r and \n
(() => {
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Can you drop this style and just wrap this portion of the test in curly braces. That will provide the block scope you want.

@Fishrock123
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@princejwesley Could you give an example as to how to induce the problem this fixes?

\r\n (\n after \r) is a grapheme iirc aka one character

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princejwesley commented Aug 15, 2016

@Fishrock123

This is how I reproduced in macOS. Run the below snippet and hit enter/return for (\r) and ctrl + j for (\n). You can try with repl too.

const readline = require('readline');

const rli = new readline.Interface({
    input: process.stdin,
    output: process.stdout,
    terminal: true
});
let count = 0;
rli.on('line', function(line) {
    count++;
    console.log(`line event triggered ${count}`);
});

Edit: \r\n - two characters. Here is the interesting history behind it

@jasnell
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jasnell commented Aug 15, 2016

It may be better to make the delay period configurable

@mscdex
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mscdex commented Aug 15, 2016

I think if we're going to add a delay, it should definitely be configurable (with some sensible default but allowing to opt out altogether -- perhaps with a 0 value).

@princejwesley
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@mscdex Delay is introduced to differentiate whether its a system that emits \r\n for a single newline or a user or both. Setting delay as zero will nullify this fix.

In nutshell, this PR tries to figure out whether \n is an individual event or the tail of \r(emitted by the system for newline).

Current experience,

~ 🙈 node
> // I hit enter - that emits CR(\r)
> // now I hit `ctrl + j ` to emit LF(\n) - no newline

@mscdex
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mscdex commented Aug 15, 2016

@princejwesley I understand, but I think it would be useful to be able to explicitly tell readline what to check for instead of trying to guess by adding a delay, whether that's setting 0 for the delay or setting some other option/flag.

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@mscdex I'll update the PR with configurable option. Shall I use crLfDelay or any better name?

}
return rl;
};


function Interface(input, output, completer, terminal) {
function Interface(input, output, completer, terminal,
crLfDelay = kCRLFDelayInMillis) {
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IMHO this should line up with the input parameter.

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mscdex commented Aug 15, 2016

@princejwesley I don't really have a preference on the name. Although personally I think if it starts with 'CRLF', that prefix would look better lowercased (crlf) instead of mixed cased (crLf).

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@Trott Trott added the semver-minor PRs that contain new features and should be released in the next minor version. label Aug 16, 2016
@@ -358,6 +358,9 @@ added: v0.1.98
only if `terminal` is set to `true` by the user or by an internal `output`
check, otherwise the history caching mechanism is not initialized at all.
* `prompt` - the prompt string to use. Default: `'> '`
* `crlfDelay` {number} If the delay between `\r` and `\n` exceeds
`crlfDelay`, both `\r` and `\n` will be treated as separate end-of-line
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Suggestion: s/exceeds crlfDelay/exceeds crlfDelay milliseconds

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also... should there be a maximum delay? And how does one turn off the delay entirely? In other APIs, we've used setting the value explicitly to 0 or null or Infinity to turn it off.

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I am not sure about the maximum delay but minimum delay should not be zero. the reason is subsequent events(\r followed by \n) may have latency greater than or equal to 1ms. It will obviously break windows system.
What do you suggest ? 10ms as minimum delay?

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That should work.

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I am afraid to put 10ms (seems low because of context switches and other factors). Now I set [100, 2000] as range. It will go few more rounds to come up with better range 😄

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Another attempt, CI: https://ci.nodejs.org/job/node-test-pull-request/3766/

rli = new readline.Interface({ input: fi, output: fi, crlfDelay: 1 << 30});
assert.strictEqual(rli.crlfDelay, 2000);
rli.close();
}
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To 3 separate scopes?

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@yorkie done

callCount++;
});
fi.emit('data', '\r');
setTimeout(() => {
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Wrap this function with common.mustCall?

@yorkie
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yorkie commented Aug 24, 2016

LGTM :)

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@jasnell @Fishrock123 @mscdex PTAL

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jasnell commented Aug 26, 2016

LGTM

1 similar comment
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mscdex commented Aug 26, 2016

LGTM

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Trying again for green build: https://ci.nodejs.org/job/node-test-pull-request/3865/

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jasnell commented Aug 30, 2016

build bot failure on the last CI run... trying one final time for green: https://ci.nodejs.org/job/node-test-pull-request/3897/

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@jasnell failed again 😞

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jasnell commented Aug 31, 2016

@nodejs/build @jbergstroem ... can someone take a look to see what's happening with the arm build bot on this?

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princejwesley commented Sep 2, 2016

ping @nodejs/build

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@jasnell I see full of red & unstable CI jobs. I'll trigger build after few days to get green build

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We've fixed the arm issues; disk-related. Please try again!

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princejwesley commented Sep 5, 2016

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@jbergstroem last two build attempts - unstable. can you take a look?

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@princejwesley 3959,3960 looked good though! Flaky is fine -- it means a test is known to fail.

princejwesley added a commit that referenced this pull request Sep 8, 2016
Emit two line events when there is a delay between
CR('\r') and LF('\n').

Introduced a new option `crlfDelay`. If the delay between \r and \n
exceeds `crlfDelay` milliseconds, both \r and \n will be treated as
separate end-of-line input. Default to 100 milliseconds.
`crlfDelay` will be coerced to [100, 2000] range.

PR-URL: #8109
Reviewed-By: Yorkie Liu <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Brian White <[email protected]>
@princejwesley
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Landed in a634554

Fishrock123 pushed a commit that referenced this pull request Sep 14, 2016
Emit two line events when there is a delay between
CR('\r') and LF('\n').

Introduced a new option `crlfDelay`. If the delay between \r and \n
exceeds `crlfDelay` milliseconds, both \r and \n will be treated as
separate end-of-line input. Default to 100 milliseconds.
`crlfDelay` will be coerced to [100, 2000] range.

PR-URL: #8109
Reviewed-By: Yorkie Liu <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Brian White <[email protected]>
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