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regexp/syntax: \Z not documented/implemented #14793

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perillo opened this issue Mar 12, 2016 · 6 comments
Closed

regexp/syntax: \Z not documented/implemented #14793

perillo opened this issue Mar 12, 2016 · 6 comments
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Go1.7

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@perillo
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perillo commented Mar 12, 2016

Please answer these questions before submitting your issue. Thanks!

  1. What version of Go are you using (go version)?

go1.6 linux/amd

The documentation of the regexp/syntax package, in the "Empty strings" sections, says:

$              at end of text (like \z not \Z) or line (flag m=true)

However \Z is not documented, and it does not appear in the source code, except this comment in the (*Regex).Equal method:

// The parse flags remember whether this is \z or \Z.
@bradfitz bradfitz added this to the Go1.7 milestone Mar 12, 2016
@bradfitz
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/cc @rsc for thoughts

@perillo
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perillo commented Mar 12, 2016

git log -p regexp/syntax | grep -w '\\Z' reports:

   $              at end of text (like \z not \Z) or line (flag m=true)
+  $              at end of text (like \z not \Z) or line (flag m=true)
+       // The parse flags remember whether this is \z or \Z.

It seems that \Z is a typo or it was a planned feature never implemented.

@junyer
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junyer commented Mar 14, 2016

It seems that \Z is a typo or it was a planned feature never implemented.

The WasDollar flag in RE2 – and in Go – is for distinguishing between $ and \z. As such, the comment at https://github.com/golang/go/blob/master/src/regexp/syntax/regexp.go#L71 should be corrected.

The regexp/syntax documentation does not describe \Z, so it might not be helpful to mention it when describing $. https://golang.org/s/re2syntax does describe \Z as "at end of text, or before newline at end of text (NOT SUPPORTED)".

@rsc
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rsc commented May 18, 2016

If someone wants to change "not \Z" to "not Perl's \Z", LGTM.

@bradfitz
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https://go-review.googlesource.com/23201

@gopherbot
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CL https://golang.org/cl/23201 mentions this issue.

@golang golang locked and limited conversation to collaborators May 18, 2017
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