[bug]This regular expression code will report an error about scala-native HOT 9 CLOSED

fenginsc,

Thank you for reporting this defect. Sorry that you are experiencing it.

The provided code made it easier to take a first look at this.

I confirm that the provided code works using scala-cli with Scala 3.3.1, & JVM (17) and
fails with Scala Native 4.16 (and probably others, including 5.0-SNAPSHOT).

The difference in my configuration is that I am using Linux (6.6.8).

I suggest removing the "on windows" from the topic line now that the defect
has been reproduced on another OS. I do not have the privs necessary to do that edit.

I am off to see if I can minimize the regex.

from scala-native.

I confirmed this works in Scala JVM as well.

from scala-native.

Eric, thank you for the data. OS? I presume macOS.

from scala-native.

Next Step:

• I need to check the RE2 GitHub website to see if there are fixes there which might resolve this Issue.

• Looks like SN regex was last updated to re2j version 1.3 about two years ago. re2j is now at 1.7.

• There is one fix in re2j to a bug in its original Go code which deals with parsing OR conditions.
  google/re2j#93 "Incorrect match found when capturing groups are not used"
  Next sprint I may try creating a reproducer which creates groups for only the common prefix
  in the original regex. That may tell me/us if we are on the trail of a solution or just a path-to-nowhere.

• Later: original regex with grouping of only the OR clauses with a common prefix works. So next
  step is to study the re2j fix and possibly port it.
  "^(\\-|\\+)?(0\\.[0-9]+|([1-9][0-9]*\\.[0-9]+)|([1-9][0-9]*)|0)$"

Progress:

• I have been able to isolate a simpler reproducer. This may not be the simplest reproducer
  but it is what I have not. The presence and placement of the grouping parentheses and
  the presence of the OR operator seem to be important.

• The working goal is for SN to parse the presented Regex.
  I have been able to create a slightly altered Regex which works for both SN & JVM.
  The idea is to understand the problem by perturbing the inputs: here manually grouping the
  clauses of OR operators.
  ^(\\-|\\+)?(0\\.[0-9]+)|([1-9][0-9]*\\.[0-9]+)|([1-9][0-9]*)|0$

• I think I have run out of cleverness for this year.

from scala-native.

So that I understand, is the original regex just to illustrate the problem or is it intended to be
used in production?

If the latter, is the intent that inputs have been put in some cannonical form so that then
regex need not recognize otherwise valid numbers such as "00" or "02.3"?

from scala-native.

Thank you, I've changed the title, it was just an exercise to test if a string was a legitimate number, obviously "00" or "02.3" is not a mathematically legitimate number.

from scala-native.

re: obviously "00" or "02.3" is not a mathematically legitimate number.

That is not so obvious to Java. Running each of the lines below in scastie
succeeds and returns the expected value.

Granted that those strings do not represent the canonical or most reduced
form of a Platonic number.

java.lang.Integer.parseInt("00")
java.lang.Double.parseDouble("01.618")

from scala-native.

@fenginsc

At first blush, this defect looked like the defect reported fixed in PRs #2410 & #1701. They were merged into Scala Native
4.n & 5.n two plus years ago.

Further study narrowed the defect down to a mistake I made porting from the original re2j code five or so
years ago. I apologize for the time you have spent on my error and the inconvenience it caused.

Thank you, once again, for flushing it out and reporting it.

PR #3642 contains a fix and corresponding test.

I have marked that PR for backporting to the 4.n stream.

I do not know when the next 4.n release will be. A release of Scala itself is coming up and
Scala Native 4.n release which supports the new Scala is usually released very soon after.

Until then, can you use the workaround of using parenthesis around any OR clause which
has more than two elements? In "(a+b+c+)| z" the first clause has three elements. Without
the parentheses, I believe that will provoke the reported defect. With them, I believe that
Scala Native will handle the string.

If you can not use the workaround, let me know here and I will see what else I might be able
to figure out.

This one was a pretty good brain teaser.

from scala-native.

@LeeTibbert
Thank you very much for fixing this issue, I've fixed it by simplifying that regular expression ran my program successfully.
"^[-+]?(0|[1-9][0-9]*)(\\.[0-9]+)?$"
So I don't need the previous regular expression anymore, it's just an example to demonstrate the bug.
happy new year!

from scala-native.