Streamline xparse interface

[nickrobinson251]

I think we have too many different xparse methods that set different defaults.

julia> Parsers.xparse(String, str)  # == Parsers.xparse(String, str; quoted=true)
options.quoted = true
Parsers.Result{PosLen}(-32603, 15, PosLen(0x0000000000200003))

julia> Parsers.xparse(String, str, 1, sizeof(str))
options.quoted = true
Parsers.Result{PosLen}(-32603, 15, PosLen(0x0000000000200003))

julia> Parsers.xparse(String, str, 1, sizeof(str), Parsers.Options())
options.quoted = false
Parsers.Result{PosLen}(33, 15, PosLen(0x000000000010000f))

julia> Parsers.xparse(String, str, 1, sizeof(str), Parsers.Options(; quoted=true))
options.quoted = true
Parsers.Result{PosLen}(5, 6, PosLen(0x0000000000200003))

1. The first hits this, which passes quoted::Bool=true:
   

   Parsers.jl/src/Parsers.jl

   Lines 211 to 212 in e2259a6

   # for testing purposes only, it's much too slow to dynamically create Options for every xparse call

   function xparse(::Type{T}, buf::Union{AbstractVector{UInt8}, AbstractString, IO}; pos::Integer=1, len::Integer=buf isa IO ? 0 : sizeof(buf), sentinel=nothing, wh1::Union{UInt8, Char}=UInt8(' '), wh2::Union{UInt8, Char}=UInt8('\t'), quoted::Bool=true, openquotechar::Union{UInt8, Char}=UInt8('"'), closequotechar::Union{UInt8, Char}=UInt8('"'), escapechar::Union{UInt8, Char}=UInt8('"'), ignorerepeated::Bool=false, ignoreemptylines::Bool=false, delim::Union{UInt8, Char, PtrLen, AbstractString, Nothing}=UInt8(','), decimal::Union{UInt8, Char}=UInt8('.'), comment=nothing, trues=nothing, falses=nothing, dateformat::Union{Nothing, String, Dates.DateFormat}=nothing, debug::Bool=false, stripwhitespace::Bool=false, stripquoted::Bool=false) where {T}

2. The second hits this, which uses Parsers.XOPTIONS
   

   Parsers.jl/src/Parsers.jl

   Lines 217 to 218 in e2259a6

   	xparse(::Type{T}, buf::AbstractString, pos, len, options=Parsers.XOPTIONS) where {T} =
   	xparse(T, codeunits(buf), pos, len, options)

   • and XOPTIONS has quoted=true
     

     Parsers.jl/src/Parsers.jl

     Line 164 in e2259a6

     const XOPTIONS = Options(missing, UInt8(' '), UInt8('\t'), UInt8('"'), UInt8('"'), UInt8('"'), UInt8(','), UInt8('.'), nothing, nothing, nothing, false, false, nothing, true, false, false)

   • (aside: Why does XOPTIONS exist?)

3. The third hits the same method as 2, but passing in Parsers.Options() which has quoted=false:
   

   Parsers.jl/src/Parsers.jl

   Line 157 in e2259a6

   quoted::Bool=false,

4. The fourth hits the same method as 2/3, but passes in Parsers.Options(; quoted=true) to set that explicitly ...but returns a different answer to 1 (xparse(String, str; quoted=true)), because Options() defaults to delim=nothing whereas 1 sets delim=UInt8(',')
   

   Parsers.jl/src/Parsers.jl

   Line 149 in e2259a6

   delim::Union{Nothing, UInt8, Char, String}=nothing,

This is now very off-topic from your original issue (sorry), so can move it to a new issue, but i think perhaps we could simplify the xparse interface to make this whole thing a little less confusing / more explicit.

I think i'd be in favour of requiring a user-given ::Options argument.

cc @quinnj

Originally posted by @nickrobinson251 in #119 (comment)

[quinnj]

I think this is pretty well cleaned up on #main.