Suppor dimensional metadata

Project.toml

@@ -1,7 +1,7 @@
 name = "DataAPI"
 uuid = "9a962f9c-6df0-11e9-0e5d-c546b8b5ee8a"
 authors = ["quinnj <[email protected]>"]
-version = "1.15.0"
+version = "1.16.0"
 
 [compat]
 julia = "1"

src/DataAPI.jl

@@ -472,15 +472,17 @@ end
     colmetadatakeys(x, [col])
 
 If `col` is passed return an iterator of metadata keys for which
-`metadata(x, col, key)` returns a metadata value. Throw an error if `x` does not
+`colmetadata(x, col, key)` returns a metadata value. Throw an error if `x` does not
 support reading column metadata or if `col` is not a column of `x`.
 
 `col` must have a type that is supported by table `x` for column indexing.
 Following the Tables.jl contract `Symbol` and `Int` are always allowed.
 
 If `col` is not passed return an iterator of `col => colmetadatakeys(x, col)`
 pairs for all columns that have metadata, where `col` are `Symbol`.
-If `x` does not support column metadata return `()`.
+
+If `colmetadatasupport(typeof(x)).read` or `colmetadatasupport(typeof(x)).write` return `true`
+this should also be defined.
 """
 function colmetadatakeys end
 
@@ -515,6 +517,109 @@ Throw an error if `x` does not support metadata deletion for column `col`.
 """
 function emptycolmetadata! end
 
+"""
+    dimmetadatasupport(T::Type, dim::Int)
+
+Return a `NamedTuple{(:read, :write), Tuple{Bool, Bool}}` indicating whether
+values of type `T` support metadata correspond to dimension `dim`.
+
+The `read` field indicates whether reading metadata with the [`dimmetadata`](@ref)
+and [`dimmetadatakeys`]](@ref) functions is supported.
+
+The `write` field indicates whether modifying metadata with the [`dimmetadata!`](@ref),
+[`deletemetadata!`](@ref), and [`emptymetadata!`](@ref) functions is supported.
+"""
+dimmetadatasupport(::Type, i::Int) = (read=false, write=false)
+
+"""
+    dimmetadata(x, dim::Int, key::AbstractString, [default]; style::Bool=false)
+
+Return metadata value associated with `x` for dimension `dim` and key `key`.
+Throw an error if `x` does not support reading metadata for dimension `dim` or `x`
+supports reading metadata, but does not have a mapping for dimension `dim` for `key`.
+
+If `style=true` return a tuple of metadata value and metadata style. Metadata
+style is an additional information about the kind of metadata that is stored for
+the `key`.
+
+$STYLE_INFO
+
+If `default` is passed then return it if `x` supports reading metadata and has
+dimension `dim` but mapping for `key` is missing.
+If `style=true` return `(default, :default)`.
+"""
+function dimmetadata end
+
+"""
+    dimmetadata(x, dim::Int; style::Bool=false)
+
+Return a dictionary of metadata corresponding to dimension `dim` of object `x`. If `dim`
+ is not passed return a collection mapping each dimension to its metadata so that
+`collection[dim][key] == dimmetadata(x, dim, key)`.
+Throw an error if `x` does not support reading metadata corresponding to dimension `dim`.
+
+If `style=true` values are tuples of metadata value and metadata style. Metadata
+style is an additional information about the kind of metadata that is stored for
+the `key`.
+
+$STYLE_INFO
+
+The returned object may be freshly allocated on each call to `dimmetadata` and
+is considered to be owned by `x` so it must not be modified.
+"""
+function dimmetadata(x::T, dim::Int; style::Bool=false) where {T}
+    if !dimmetadatasupport(T, dim).read
+        throw(ArgumentError("Objects of type $T do not support reading dimension metadata"))
+    end
+    return Dict(key => dimmetadata(x, dim, key, style=style) for key in dimmetadatakeys(x, dim))
+end
+function dimmetadata(x::T; style::Bool=false) where {T}
+    Tuple(dimmetadata(x, dim; style=style) for dim in 1:ndims(x))
+end
+
+"""
+    dimmetadatakeys(x, [dim::Int])
+
+If `dim` is passed return an iterator of metadata keys for which
+`dimmetadata(x, dim, key)` returns a metadata value. Throw an error if `x` does not
+support reading dimension metadata or if `dim` is not a dimension of `x`.
+
+If `dim` is not passed return an iterator of `dim => dimmetadatakeys(x, dim)`
+pairs for all dimensions that have metadata.
+
+If `dimmetadatasupport(typeof(x)).read` or `dimmetadatasupport(typeof(x)).write` return `true`
+this should also be defined.
+"""
+function dimmetadatakeys end
+
+"""
+    dimmetadata!(x, dim::Int, key::AbstractString, value; style::Symbol=:default)
+
+Set metadata for `x` for dimension `dim` for key `key` to have value `value`
+and style `style` (`:default` by default) and return `x`.
+Throw an error if `x` does not support setting metadata for dimension `dim`.
+
+$STYLE_INFO
+"""
+function dimmetadata! end
+
+"""
+    deletedimmetadata!(x, dim::Int, key::AbstractString)
+
+Delete metadata corresponding to dimension `dim` of `x` for key `key` and return `x`
+(if metadata for `key` is not present do not perform any action).
+Throw an error if `x` does not support metadata deletion for dimension `dim`.
+"""
+function deletedimmetadata! end
+
+"""
+    emptydimmetadata!(x, dim::Int)
+
+Delete all metadata for `x` corresponding to dimension `dim` and return `x`.
+Throw an error if `x` does not support metadata deletion for dimension `dim`.
+"""
+function emptydimmetadata! end
+
 """
     rownumber(row)
 

test/runtests.jl

@@ -17,12 +17,23 @@ DataAPI.levels(x::TestArray) = reverse(DataAPI.levels(x.x))
 struct TestMeta
     table::Dict{String, Any}
     col::Dict{Symbol, Dict{String, Any}}
+    dims::Tuple{Dict{String, Any}, Dict{String, Any}}
 
-    TestMeta() = new(Dict{String, Any}(), Dict{Symbol, Dict{String, Any}}())
+    function TestMeta()
+        new(Dict{String, Any}(), Dict{Symbol, Dict{String, Any}}(), (Dict{String, Any}(), Dict{String, Any}()))
+    end
 end
+Base.ndims(::TestMeta) = 2
 
 DataAPI.metadatasupport(::Type{TestMeta}) = (read=true, write=true)
 DataAPI.colmetadatasupport(::Type{TestMeta}) = (read=true, write=true)
+function DataAPI.dimmetadatasupport(::Type{TestMeta}, dim::Int)
+    if dim == 1 || dim == 2
+        (read=true, write=true)
+    else
+        (read=false, write=false)
+    end
+end
 
 function DataAPI.metadata(x::TestMeta, key::AbstractString; style::Bool=false)
     return style ? x.table[key] : x.table[key][1]
@@ -93,6 +104,38 @@ end
 
 DataAPI.emptycolmetadata!(x::TestMeta) = empty!(x.col)
 
+function DataAPI.dimmetadata(x::TestMeta, dim::Int, key::AbstractString; style::Bool=false)
+    return style ? x.dims[dim][key] : x.dims[dim][key][1]
+end
+
+function DataAPI.dimmetadata(x::TestMeta, dim::Int, key::AbstractString, default; style::Bool=false)
+    haskey(x.dims[dim], key) && return DataAPI.metadata(x, dim, key, style=style)
+    return style ? (default, :default) : default
+end
+
+function DataAPI.dimmetadatakeys(x::TestMeta, dim::Int)
+    if DataAPI.dimmetadatasupport(TestMeta, dim).read
+        return keys(x.dims[dim])
+    else
+        return ()
+    end
+end
+
+function DataAPI.dimmetadata!(x::TestMeta, dim::Int, key::AbstractString, value; style::Symbol=:default)
+    x.dims[dim][key] = (value, style)
+    return x
+end
+
+function DataAPI.deletedimmetadata!(x::TestMeta, dim::Int, key::AbstractString)
+    delete!(x.dims[dim], key)
+    return x
+end
+function DataAPI.emptydimmetadata!(x::TestMeta, dim::Int)
+    empty!(x.dims[dim])
+    return x
+end
+
+
 # An example implementation of a table (without the Tables.jl interface)
 # for testing DataAPI.rownumber
 struct TestTable{T}
@@ -301,12 +344,23 @@ end
     @test_throws MethodError DataAPI.colmetadatakeys(1, 1)
     @test_throws MethodError DataAPI.colmetadatakeys(1)
 
+    @test_throws MethodError DataAPI.dimmetadata!(1, 1, "a", 10, style=:default)
+    @test_throws MethodError DataAPI.deletedimmetadata!(1, 1, "a")
+    @test_throws MethodError DataAPI.emptydimmetadata!(1, 1)
+    @test_throws MethodError DataAPI.dimmetadata(1, 1, "a")
+    @test_throws ArgumentError DataAPI.dimmetadata(1, 1)
+    @test_throws MethodError DataAPI.dimmetadata(1, 1, "a", style=true)
+    @test_throws ArgumentError DataAPI.dimmetadata(1, 1, style=true)
+
     @test DataAPI.metadatasupport(Int) == (read=false, write=false)
     @test DataAPI.colmetadatasupport(Int) == (read=false, write=false)
+    @test DataAPI.dimmetadatasupport(Int, 1) == (read=false, write=false)
 
     tm = TestMeta()
     @test DataAPI.metadatasupport(TestMeta) == (read=true, write=true)
     @test DataAPI.colmetadatasupport(TestMeta) == (read=true, write=true)
+    @test DataAPI.dimmetadatasupport(TestMeta, 1) == (read=true, write=true)
+    @test DataAPI.dimmetadatasupport(TestMeta, 0) == (read=false, write=false)
 
     @test isempty(DataAPI.metadatakeys(tm))
     @test DataAPI.metadata(tm) == Dict()
@@ -353,6 +407,28 @@ end
     @test DataAPI.colmetadata!(tm, :col, "a", "100", style=:note) == tm
     DataAPI.emptycolmetadata!(tm)
     @test isempty(DataAPI.colmetadatakeys(tm))
+
+    @test isempty(DataAPI.dimmetadatakeys(tm, 1))
+    @test isempty(DataAPI.dimmetadatakeys(tm)[1])
+    @test DataAPI.dimmetadata(tm, 1) == Dict()
+    @test DataAPI.dimmetadata(tm) == (Dict(), Dict())
+    @test DataAPI.dimmetadata(tm, 1, style=true) == Dict()
+    @test DataAPI.dimmetadata!(tm, 1, "a", "100", style=:note) == tm
+    @test collect(DataAPI.dimmetadatakeys(tm, 1)) == ["a"]
+    @test_throws KeyError DataAPI.dimmetadata(tm, 1, "b")
+    @test DataAPI.dimmetadata(tm, 1, "b", 123) == 123
+    @test_throws KeyError DataAPI.dimmetadata(tm, 1, "b", style=true)
+    @test DataAPI.dimmetadata(tm, 1, "b", 123, style=true) == (123, :default)
+    @test DataAPI.dimmetadata(tm, 1, "a") == "100"
+    @test DataAPI.dimmetadata(tm, 1) == Dict("a" => "100")
+    @test DataAPI.dimmetadata(tm)[1] == Dict("a" => "100")
+    @test DataAPI.dimmetadata(tm, 1, "a", style=true) == ("100", :note)
+    @test DataAPI.dimmetadata(tm, 1, style=true) == Dict("a" => ("100", :note))
+    DataAPI.deletedimmetadata!(tm, 1, "a")
+    @test isempty(DataAPI.dimmetadatakeys(tm, 1))
+    @test DataAPI.dimmetadata!(tm, 1, "a", "100", style=:note) == tm
+    DataAPI.emptydimmetadata!(tm, 1)
+    @test isempty(DataAPI.dimmetadatakeys(tm, 1))
 end
 
 @testset "rownumber" begin