rsplit error on empty strings

[elbrook33]

Hi, in case it's unintentional, rsplit gives me an error for empty strings in 1.6, it used to give [""]. Thanks!

[bicycle1885]

Hi, can you show us a minimal example?

[elbrook33]

It only seems to happen when the separator is at least 2. a = "" rsplit(a, "1") 1-element Vector{SubString{String}}: "" rsplit(a, "12") ERROR: BoundsError: attempt to access 0-element Vector{UInt8} at index [0] Stacktrace: [1] _rsearchindex(s::Vector{UInt8}, t::Vector{UInt8}, _k::Int64) @ Base ./strings/search.jl:461 [2] _rsearchindex(s::String, t::String, i::Int64) @ Base ./strings/search.jl:446 [3] _rsearch @ ./strings/search.jl:523 [inlined] [4] findprev @ ./strings/search.jl:556 [inlined] [5] findlast @ ./strings/search.jl:363 [inlined] [6] _rsplit(str::String, splitter::String, limit::Int64, keepempty::Bool, strs::Vector{SubString{String}}) @ Base ./strings/util.jl:492 [7] #rsplit#377 @ ./strings/util.jl:479 [inlined] [8] rsplit(str::String, splitter::String) @ Base ./strings/util.jl:479 [9] top-level scope @ REPL[16]:1

…

On Sat, 2021-03-27 at 20:27 -0700, Kenta Sato wrote: Hi, can you show us a minimal example? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub, or unsubscribe.

[bicycle1885]

Thank you. I can reproduce the problem now.

Julia 1.5.4:

julia> rsplit("", "//")
1-element Array{SubString{String},1}:
 ""

Julia 1.6.0:

julia> rsplit("", "//")
ERROR: BoundsError: attempt to access 0-element Vector{UInt8} at index [0]
Stacktrace:
 [1] _rsearchindex(s::Vector{UInt8}, t::Vector{UInt8}, _k::Int64)
   @ Base ./strings/search.jl:461
 [2] _rsearchindex(s::String, t::String, i::Int64)
   @ Base ./strings/search.jl:446
 [3] _rsearch
   @ ./strings/search.jl:523 [inlined]
 [4] findprev
   @ ./strings/search.jl:556 [inlined]
 [5] findlast
   @ ./strings/search.jl:363 [inlined]
 [6] _rsplit(str::String, splitter::String, limit::Int64, keepempty::Bool, strs::Vector{SubString{String}})
   @ Base ./strings/util.jl:492
 [7] #rsplit#377
   @ ./strings/util.jl:479 [inlined]
 [8] rsplit(str::String, splitter::String)
   @ Base ./strings/util.jl:479
 [9] top-level scope
   @ REPL[6]:1

[reallyasi9]

For an additional data point, the same error results from attempting an rsplit where the first characters of the string match the split pattern:

julia> versioninfo()
Julia Version 1.6.1
Commit 6aaedecc44 (2021-04-23 05:59 UTC)
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: Intel(R) Core(TM) i7-8650U CPU @ 1.90GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-11.0.1 (ORCJIT, skylake)

julia> rsplit("hello", "he")
ERROR: BoundsError: attempt to access 5-element Vector{UInt8} at index [0]
Stacktrace:
 [1] _rsearchindex(s::Vector{UInt8}, t::Vector{UInt8}, _k::Int64)
   @ Base .\strings\search.jl:461
 [2] _rsearchindex(s::String, t::String, i::Int64)
   @ Base .\strings\search.jl:446
 [3] _rsearch
   @ .\strings\search.jl:523 [inlined]
 [4] findprev
   @ .\strings\search.jl:556 [inlined]
 [5] _rsplit(str::String, splitter::String, limit::Int64, keepempty::Bool, strs::Vector{SubString{String}})
   @ Base .\strings\util.jl:497
 [6] #rsplit#377
   @ .\strings\util.jl:479 [inlined]
 [7] rsplit(str::String, splitter::String)
   @ Base .\strings\util.jl:479
 [8] top-level scope
   @ REPL[3]:1

But matching a single character works:

julia> rsplit("hello", "h")
2-element Vector{SubString{String}}:
 ""
 "ello"

And split works:

julia> split("hello", "lo")
2-element Vector{SubString{String}}:
 "hel"
 ""

[KristofferC]

I think this is the same as #39401. cc @Moelf