invalid character index in findfirst

[Keno]

julia> findfirst("⨳(",'(')
ERROR: UnicodeError: invalid character index
 in next(::UTF8String, ::Int64) at ./version.jl:106
 [inlined code] from ./strings/basic.jl:37
 in findnext(::UTF8String, ::Char, ::Int64) at ./array.jl:664
 in findfirst(::UTF8String, ::Char) at ./array.jl:670
 in eval(::Module, ::Any) at ./docs/bootstrap.jl:69

[vtjnash]

it looks like it's trying to treat the string as an array, but also assumes that arrays are indexed as 1:1:length(array) (ref #15434 (comment))

[JeffBezanson]

Those functions might need an ::AbstractArray on the first argument. Right now they're Any.

[Keno]

There is search for string, so that would be fine.

[nalimilan]

Restricting the signature sounds like the best solution, and at some point we may want to add a specialized version for AbstractString to unify the API (#5664, #10593).

[nalimilan]

That said, it looks like it should be easy to generalize to any iterable and index type, returning the state from next as the index. Maybe we should decide that the iteration state must be usable as an index when a type supports indexing? Or create an Indexable trait to which this would apply?

[Keno]

Ran into this again:

julia> findnext("λ\n",'\n',1)
ERROR: UnicodeError: invalid character index
Stacktrace:
 [1] slow_utf8_next(::Ptr{UInt8}, ::UInt8, ::Int64, ::Int64) at ./strings/string.jl:172
 [2] next at ./strings/string.jl:204 [inlined]
 [3] getindex(::String, ::Int64) at ./strings/basic.jl:32
 [4] findnext(::String, ::Char, ::Int64) at ./array.jl:1213

julia> search("λ\n",'\n',1)
3

julia> findnext("a\n",'\n',1)
2

julia> search("a\n",'\n',1)
2

Putting on the 1.0 milestone since restricting the find functions after would be breaking.

[StefanKarpinski]

Would potentially be fixed by @JeffBezanson's proposal in #10593.