Merge pull request #33 from eliascarv/colspec-dropmissing

Implementing ColSpec interface in DropMissing

src/transforms/filter.jl

@@ -42,6 +42,7 @@ const VecOrTuple{T} = Union{Vector{T}, NTuple{N, T}} where {T, N}
 
 """
     DropMissing()
+    DropMissing(:)
 
 Drop all rows with missing values in table.
 
@@ -55,20 +56,35 @@ Drop all rows with missing values in selects columns `col₁`, `col₂`, ..., `c
 
 Drop all rows with missing values in columns that match with `regex`.
 """
-DropMissing() = Filter(row -> all(!ismissing, row))
+struct DropMissing{S<:ColSpec} <: Stateless
+  colspec::S
+end
 
-DropMissing(cols::VecOrTuple{T}) where {T<:Union{Symbol, Integer}} =
-  Filter(row -> all(!ismissing, getindex.(Ref(row), cols)))
+DropMissing(::Tuple{}) = throw(ArgumentError("Cannot create a DropMissing object with empty tuple."))
 
-DropMissing(cols::VecOrTuple{T}) where {T<:AbstractString} =
-  DropMissing(Symbol.(cols))
+DropMissing() = DropMissing(:)
 
 DropMissing(cols::T...) where {T<:ColSelector} =
   DropMissing(cols)
 
-function DropMissing(regex::Regex)
-  Filter() do row
-    cols = _filter(regex, propertynames(row))
-    all(!ismissing, getindex.(Ref(row), cols))
-  end
+isrevertible(::Type{<:DropMissing}) = true
+
+_ftrans(::DropMissing{Colon}, table) =
+  Filter(row -> all(!ismissing, row))
+
+function _ftrans(transform::DropMissing, table)
+  allcols = Tables.columnnames(table)
+  cols = _filter(transform.colspec, allcols)
+  Filter(row -> all(!ismissing, getindex.(Ref(row), cols)))
+end
+
+function apply(transform::DropMissing, table)
+  ftrans = _ftrans(transform, table)
+  newtable, fcache = apply(ftrans, table)
+  newtable, (ftrans, fcache)
+end
+
+function revert(::DropMissing, newtable, cache)
+  ftrans, fcache = cache
+  revert(ftrans, newtable, fcache)
 end

test/transforms.jl

@@ -603,6 +603,22 @@
     n1, c1 = apply(T, t)
     n2 = reapply(T, t, c1)
     @test n1 == n2
+
+    # throws: empty tuple
+    @test_throws ArgumentError DropMissing(())
+
+    # throws: empty selection
+    @test_throws AssertionError apply(DropMissing(r"g"), t)
+    @test_throws AssertionError apply(DropMissing(Symbol[]), t)
+    @test_throws AssertionError apply(DropMissing(String[]), t)
+
+    # throws: columns that do not exist in the original table
+    @test_throws AssertionError apply(DropMissing(:g, :h), t)
+    @test_throws AssertionError apply(DropMissing([:g, :h]), t)
+    @test_throws AssertionError apply(DropMissing((:g, :h)), t)
+    @test_throws AssertionError apply(DropMissing("g", "h"), t)
+    @test_throws AssertionError apply(DropMissing(["g", "h"]), t)
+    @test_throws AssertionError apply(DropMissing(("g", "h")), t)
   end
 
   @testset "Rename" begin