Add some methods to make JLSOFile more Dict-like

[nickrobinson251]

• adds keys, haskey, get and get! for JLSOFile (but not iterate as i didn't have a use-cae for it); closes Should JLSOFile have get, get!, keys and haskey methods #107
• fixes JLSOFile() to return a JLSOFile, whereas on master it errrors:

  julia> JLSOFile()
  ERROR: MethodError: no method matching JLSOFile(::Dict{Union{}, Union{}}; version=v"4.0.0", julia=v"1.6.0", format=:julia_serialize, compression=:gzip, image="")
  Closest candidates are:
  JLSOFile(::Any, ::Any, ::Any, ::Any, ::Any, ::Any, ::Any, ::Any, ::Any) at /Users/nick/repos/JLSO.jl/src/JLSOFile.jl:2 got unsupported keyword arguments "version", "julia", "format", "compression", "image"
  JLSOFile(; version, julia, format, compression, image, kwargs...) at /Users/nick/repos/JLSO.jl/src/JLSOFile.jl:70
  JLSOFile(::Pair{Symbol, B} where B...; kwargs...) at /Users/nick/repos/JLSO.jl/src/JLSOFile.jl:89
  ...
  Stacktrace:
  [1] JLSOFile(; version::VersionNumber, julia::VersionNumber, format::Symbol, compression::Symbol, image::String, kwargs::Base.Iterators.Pairs{Union{}, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
   @ JLSO ~/repos/JLSO.jl/src/JLSOFile.jl:78
  [2] JLSOFile()
   @ JLSO ~/repos/JLSO.jl/src/JLSOFile.jl:78
  [3] top-level scope
   @ REPL[2]:1

• adds a save(io, ::JLSOFile) method

Together, this allows users to write code like

jlso = isfile(filename) ? read(filename, JLSOFile) : JLSOFile()
get!(jlso, :qux) do
    make_qux()
end
JLSO.save(filename, jlso)

or

if isfile(filename) 
    jlso = read(filename, JLSOFile)
    haskey(jlso, :qux) && return jlso[:qux]
else
    jlso = JLSOFile()    
end
jlso[:qux] = make_qux()
JLSO.save(filename, jlso)

The main advantage is this allows working with a JLSOFile similar to working with the Dict that would be returned by JLSO.load(filename), but with JLSOFile lazily deserialising (unlike load)

[nickrobinson251]

i don't love this magic keyword constructor, which has some "special" keywords (version, julia, ...) and then eats all the others as key/value pairs to be serialised... especially as we have a :key => value pair constructor already: JLSOFile(data::Pair{Symbol}...; kwargs...) = JLSOFile(Dict(data); kwargs...)

But I think removing this is another issue (and breaking). Maybe we should open an issue about that.

But whether we have magic-keywords or not, i think this is now the correct behjaviour for JLSOFile() (before it was a cryptic error)

[rofinn]

Yeah, :+1 for just using pairs for data objects. I think this was proposed cause some folks like creating dataframes with the keyword constructor and we often don't change the special keywords. Please open an issue to delete this method as it should be easy enough to deprecate.

[nickrobinson251]

#109

[codecov]

Codecov Report

Merging #108 (0a08047) into master (dbf7be6) will increase coverage by 0.11%.
The diff coverage is 100.00%.

❗ Current head 0a08047 differs from pull request most recent head 7c75b90. Consider uploading reports for the commit 7c75b90 to get more accurate results

@@            Coverage Diff             @@
##           master     #108      +/-   ##
==========================================
+ Coverage   97.56%   97.67%   +0.11%     
==========================================
  Files           6        6              
  Lines         205      215      +10     
==========================================
+ Hits          200      210      +10     
  Misses          5        5              

Impacted Files	Coverage Δ
src/JLSOFile.jl	93.33% <100.00%> (+2.85%)	⬆️
src/file_io.jl	94.44% <100.00%> (+0.10%)	⬆️

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[rofinn]

LGTM, would you mind bumping the minor release?

[rofinn]

Yeah, :+1 for just using pairs for data objects. I think this was proposed cause some folks like creating dataframes with the keyword constructor and we often don't change the special keywords. Please open an issue to delete this method as it should be easy enough to deprecate.