missing feature or unclear docs?

[lmiq]

Given that the JSON.json properly prints the serialized string, shouldn't the file creation just work? What am I missing?

julia> x = Dict{String,Dict{String,Float64}}("a" => Dict("a1" => 1))
Dict{String, Dict{String, Float64}} with 1 entry:
  "a" => Dict("a1"=>1.0)

julia> JSON.json(x)
"{\"a\":{\"a1\":1.0}}"

julia> JSON.json("test.dat", x)
ERROR: MethodError: no method matching JSON.Writer.PrettyContext(::IOBuffer, ::Dict{String, Dict{String, Float64}}, ::Int64, ::Bool, ::Set{UInt64}, ::Nothing)
The type `JSON.Writer.PrettyContext` exists, but no method is defined for this combination of argument types when trying to construct it.

Closest candidates are:
  JSON.Writer.PrettyContext(::T, ::Int64, ::Int64, ::Bool, ::Set{UInt64}, ::Any) where T<:IO
   @ JSON ~/.julia/packages/JSON/93Ea8/src/Writer.jl:102
  JSON.Writer.PrettyContext(::IO, ::Any, ::Any)
   @ JSON ~/.julia/packages/JSON/93Ea8/src/Writer.jl:109
  JSON.Writer.PrettyContext(::IO, ::Any)
   @ JSON ~/.julia/packages/JSON/93Ea8/src/Writer.jl:109
```

It appears that this should work from the docs here: https://juliaio.github.io/JSON.jl/stable/writing/#Core-JSON-Serialization-JSON.json

[lmiq]

Sorry, the issue is that 1.3 is not being loaded:

julia> using JSON

(mvalues) pkg> st
Status `~/Documents/Bia/mvalues/Project.toml`
  [682c06a0] JSON v1.3.0 [loaded: v0.21.4]

[lmiq]

The issue was that BenchmarkTools, in my startup file, was not updated and didn't support it. Fixed here.