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Regex to remove comments clashing with file globbing - causing hanging process #110

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jackbrewer opened this issue Jun 9, 2015 · 16 comments
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@jackbrewer
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Problem

I've run in to an issue when using Stylus file globbing for @import and @require.

Stylint process can hang indefinitely, using 100% CPU (depending on file length, and the location of the glob within the file).

Example:
@require 'components/*'

Diagnosis

It seems the regex in parse.js is catching the trailing /* of the above line and is treating it as an opening comment. As it can never find a closing comment, it keeps searching through subsequent lines, getting exponentially slower. Multiple globs in a file makes things worse.

The following gif shows a stripped back example - you can see the 'steps' in the top-right ~doubling with each new-line.

runaway-regex

Live Example - https://regex101.com/r/jU0eJ2/1

Solution

New regex which accounts for this edge-case. I know @benedfit is taking a look at possible fix, but we're finding it hard to find a solution which doesn't introduce another edge-case where an actual comment gets missed, so I thought I'd raise here in the meantime.

@benedfit
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benedfit commented Jun 9, 2015

I'm playing around with a Regex that might fix this problem: https://regex101.com/r/zM0xA6/, and including some extra test cases that might not have been previously tested against. I'll update you with my progress

@benedfit
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benedfit commented Jun 9, 2015

@rossPatton https://regex101.com/r/zM0xA6/ is close, but it wouldn't remove comments in the format /*'word'*/

@benedfit
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benedfit commented Jun 9, 2015

https://regex101.com/r/zM0xA6/6 has cracked it. Going to submit a PR shortly

Shout-out to @kuba81 and his other-worldly regex mastery

@rossPatton
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Weird, i've never hit this issue personally (and I use globs when I require) but it's awesome to see that it's already been resolved!

@rossPatton rossPatton added the bug label Jun 9, 2015
@jackbrewer
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Yeah, it's a strange one. File length definitely plays a part. Our index stylus file (mainly just @requires) is well commented/documented so is 100 lines+. It was only here that we've spotted the issue.

@rossPatton
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Interesting, I'll try to merge it in tonight.

@rossPatton
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@benedfit @jackbrewer update on this, i took a look at the pr, tests passed, looked okay, merged it into develop, but after messing with it more it seems to break things.

Playing around with it in regexr/regex101, it doesn't seem to match the same way the old regex matched.

I ended up tweaking the existing one, which seems to solve the problem: see here

It's on develop now, if you want to pull and take a look. I'll push it up to npm with confirmation that it solves the issue.

@benedfit
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@rossPatton just took a look; the new regex will ignore comments that start on the same line as an other Stylus, see https://regex101.com/r/zY7fR9/3. Is that the desired outcome?

@jackbrewer
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Tested develop and all seems to be working well. Happy to test again based on the outcome of the above comment ^

@rossPatton
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What about this? https://regex101.com/r/zY7fR9/4

@rossPatton
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I've also pushed this change up to develop, if you want to test that way.

@rossPatton
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@benedfit @jackbrewer

@benedfit
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@rossPatton tested it and it works well

@rossPatton
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Excellent!

@jackbrewer
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👍 Tested new develop changes and still fixed and working as expected.

@rossPatton
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0.9.10 fixes this issue, sorry it took so long

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