Backport #8023: Lookbehind assertion fails with /m mode enabled

• Status: Closed
• Assignee: nagachika (Tomoyuki Chikanaga)

[pietzcker (Tim Pietzcker)]

Lookbehind assertions fail if they are longer than one character, and if dotall mode is set.

irb(main):001:0> "foo" =~ /(?<=f)./m
=> 1
irb(main):002:0> "foo" =~ /(?<=fo)./m
=> nil

The latter should have matched the "o". This only seems to happen with dotall mode turned on (dot matches newline); without it, everything is OK:

irb(main):003:0> "foo" =~ /(?<=f)./
=> 1
irb(main):004:0> "foo" =~ /(?<=fo)./
=> 2

[pietzcker (Tim Pietzcker)]

Tested on Ruby 2.0.0 and 1.9.3p392

[pietzcker (Tim Pietzcker)]

Some more observations:

Adding an end-of-line anchor doesn't change anything:

irb(main):016:0> "foo" =~ /(?<=fo).*$/m
=> nil

But together with a lazy quantifier, it "works":

irb(main):017:0> "foo" =~ /(?<=fo).*?$/m
=> 2

[pietzcker (Tim Pietzcker)]

More observations:

.+ works as does its equivalent {1,}, but only in Ruby 1.9 (it seems that that's the only behavioral difference between the two in this scenario):

pry(main)> "foo" =~ /(?<=fo).+/m
=> 2
pry(main)> "foo" =~ /(?<=fo).{1,}/m
=> 2

In Ruby 2.0:

irb(main):018:0> "foo" =~ /(?<=fo).+/m
=> nil
irb(main):019:0> "foo" =~ /(?<=fo).{1,}/m
=> nil

.{0,} is busted (in both 1.9 and 2.0):

pry(main)> "foo" =~ /(?<=fo).{0,}/m
=> nil

But {n,m} works in both:

pry(main)> "foo" =~ /(?<=fo).{0,1}/m
=> 2
pry(main)> "foo" =~ /(?<=fo).{0,2}/m
=> 2
pry(main)> "foo" =~ /(?<=fo).{0,9999}/m
=> 2
pry(main)> "foo" =~ /(?<=fo).{1,999}/m
=> 2

[naruse (Yui NARUSE)]

• Status changed from Open to Closed
• % Done changed from 0 to 100

This issue was solved with changeset r39718.
Tim, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.

---

• Merge Onigmo d4bad41e16e3eccd97ccce6f1f96712e557c4518.
  fix lookbehind assertion fails with /m mode enabled. [Bug #8023]
  fix \Z matches where it shouldn't. [Bug #8001]

[naruse (Yui NARUSE)]

• Tracker changed from Bug to Backport
• Project changed from Ruby master to Backport200
• Status changed from Closed to Assigned
• Assignee set to nagachika (Tomoyuki Chikanaga)

[nagachika (Tomoyuki Chikanaga)]

• Status changed from Assigned to Closed

This issue was solved with changeset r40088.
Tim, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.

---

merge revision(s) 39718: [Backport #8001] [Backport #8023]

* Merge Onigmo d4bad41e16e3eccd97ccce6f1f96712e557c4518.
  fix lookbehind assertion fails with /m mode enabled. [Bug #8023]
  fix \Z matches where it shouldn't. [Bug #8001]