TOML

TOML

TOML.jl is a Julia standard library for parsing and writing TOML v1.0 files.

Parsing TOML data

julia> using TOML
julia> data = """
           [database]
           server = "192.168.1.1"
           ports = [ 8001, 8001, 8002 ]
       """;
julia> TOML.parse(data)
Dict{String, Any} with 1 entry:
  "database" => Dict{String, Any}("server"=>"192.168.1.1", "ports"=>[8001, 8001…

To parse a file, use TOML.parsefile. If the file has a syntax error, an exception is thrown:

julia> using TOML
julia> TOML.parse("""
           value = 0.0.0
       """)
ERROR: TOML Parser error:
none:1:16 error: failed to parse value
      value = 0.0.0
                 ^
[...]

There are other versions of the parse functions (TOML.tryparse and [TOML.tryparsefile]) that instead of throwing exceptions on parser error returns a TOML.ParserError with information:

julia> using TOML
julia> err = TOML.tryparse("""
           value = 0.0.0
       """);
julia> err.type
ErrGenericValueError::ErrorType = 14
julia> err.line
1
julia> err.column
16

Exporting data to TOML file

The TOML.print function is used to print (or serialize) data into TOML format.

julia> using TOML
julia> data = Dict(
          "names" => ["Julia", "Julio"],
          "age" => [10, 20],
       );
julia> TOML.print(data)
names = ["Julia", "Julio"]
age = [10, 20]
julia> fname = tempname();
julia> open(fname, "w") do io
           TOML.print(io, data)
       end
julia> TOML.parsefile(fname)
Dict{String, Any} with 2 entries:
  "names" => ["Julia", "Julio"]
  "age"   => [10, 20]

Keys can be sorted according to some value

julia> using TOML
julia> TOML.print(Dict(
       "abc"  => 1,
       "ab"   => 2,
       "abcd" => 3,
       ); sorted=true, by=length)
ab = 2
abc = 1
abcd = 3

For custom structs, pass a function that converts the struct to a supported type

julia> using TOML
julia> struct MyStruct
           a::Int
           b::String
       end
julia> TOML.print(Dict("foo" => MyStruct(5, "bar"))) do x
           x isa MyStruct && return [x.a, x.b]
           error("unhandled type $(typeof(x))")
       end
foo = [5, "bar"]

References

TOML.parse
TOML.parsefile
TOML.tryparse
TOML.tryparsefile
TOML.print
TOML.Parser
TOML.ParserError