Performance: long print time in stylish formatter's text-table for long report strings

[JoshuaKGoldberg]

When running npx eslint on a repository with many errors containing long descriptions and rule names, the stylish formatter can take a surprisingly long time to print results. @johnsoncodehk and I discovered this on https://github.com/johnsoncodehk/core/tree/d47d660758485c04dc26948b6ee9a42ac51a50df: more than half the command's time is spent in printResults!

The problem is a very slow /\s+$/ regex inside text-table on line 53. That regex is meant to remove all trailing whitespace in the string... which is now what String.prototype.trimEnd does.

The following fix inside text-table reduces the stylish formatter's runtime to near-zero:

        return map(row, function (c, ix) {
            // ...
-        }).join(hsep).replace(/\s+$/, '');
+        }).join(hsep).trimEnd();
    }).join('\n');

Single example time node node_modules/eslint/bin/eslint.js measurements on my M1 Max Mac Studio, with screenshots of the equivalent attached node --cpu-prof traces:

Measurement	time	Trace
Baseline	17.35s
Fixed	8.70s

• Baseline with replace regex.cpuprofile
• Fixed with string trimEnd.cpuprofile

Here is one of the strings being trimmed...

'   972  5   \x1B[33mwarning\x1B[39m  Unexpected nullable string value in conditional. Please handle the nullish/empty cases explicitly                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               \x1B[2m@typescript-eslint/strict-boolean-expressions\x1B[22m   '

The stylish formatter calls to text-table here:

eslint/lib/cli-engine/formatters/stylish.js

Line 52 in aab1b84

output += `${table(

Coincidentally, #18618 was filed last month to suggest replacing the not-updated-for-11-years text-table dependency. It was closed for lack of motivation. @jonkoops, I imagine this issue might help you feel vindicated a bit? 😄

I went ahead and published a text-table-fast package that has roughly the same API as text-table, but without the quadratic regular expression or support for the '.' alignment (which ESLint doesn't use).

Alternately, per #18618 (comment), maybe it'd make sense to extract the useful bits of text-table into stylish itself, and get rid of some overhead?

Co-authored-by: @johnsoncodehk

[nzakas]

I'd be in favor of extracting the relevant logic directly into the stylish formatter.

[jonkoops]

But in all seriousness, great performance optimization 🏎️

[jonkoops]

Got something in the works to resolve this issue, @nzakas could you assign this one to me?

[JoshuaKGoldberg]

GitHub makes it hard to assign issues to external contributors. I'll assign to myself to hold the issue but let you send a PR @jonkoops. All you! 🙂

[nzakas]

@jonkoops assigned.

@JoshuaKGoldberg as long as someone has commented on the issue, you can assign it to them. :)