Add check if input is a table before trying alternative constructors

src/other/tables.jl

@@ -31,11 +31,11 @@ fromcolumns(x, names; copycols::Bool=true) =
               copycols=copycols)
 
 function DataFrame(x::T; copycols::Bool=true) where {T}
-    if x isa AbstractVector && all(col -> isa(col, AbstractVector), x)
-        return DataFrame(Vector{AbstractVector}(x), copycols=copycols)
-    end
-    if x isa AbstractVector || x isa Tuple
-        if all(v -> v isa Pair{Symbol, <:AbstractVector}, x)
+    if !Tables.istable(x)
+        if x isa AbstractVector && all(col -> isa(col, AbstractVector), x)
+            return DataFrame(Vector{AbstractVector}(x), copycols=copycols)
+        elseif (x isa AbstractVector || x isa Tuple) &&
+            all(v -> v isa Pair{Symbol, <:AbstractVector}, x)
             return DataFrame(AbstractVector[last(v) for v in x], [first(v) for v in x],
                              copycols=copycols)
         end

test/tables.jl

@@ -53,6 +53,15 @@ Tables.schema(x::DuplicateNamesColumnTable) = Tables.Schema((:a, :a, :b), Tuple{
 Base.getproperty(d::DuplicateNamesColumnTable, nm::Symbol) = [1.0, 2.0, 3.0]
 Base.propertynames(d::DuplicateNamesColumnTable) = (:a, :a, :b)
 
+struct EmptyTableWithNames <: AbstractVector{Any}
+end
+Tables.isrowtable(::Type{EmptyTableWithNames}) = true
+Tables.rows(x::EmptyTableWithNames) = x
+Tables.schema(x::EmptyTableWithNames) = Tables.Schema((:a, :b, :c), Tuple{Float64, String, Float64})
+Base.size(x::EmptyTableWithNames) = (0,)
+Base.eltype(x::EmptyTableWithNames) = NamedTuple
+Base.iterate(x::EmptyTableWithNames, st=1) = nothing
+
 @testset "Tables" begin
     df = DataFrame(a=Int64[1, 2, 3], b=[:a, :b, :c])
 
@@ -159,6 +168,12 @@ Base.propertynames(d::DuplicateNamesColumnTable) = (:a, :a, :b)
         @test ct.b !== cat2
         @test ct.a == cat
         @test ct.b == cat == cat2
+
+        # https://github.com/JuliaData/CSV.jl/issues/702
+        df = DataFrame(EmptyTableWithNames())
+        @test size(df) == (0, 3)
+        @test names(df) == ["a", "b", "c"]
+        @test eltype.(eachcol(df)) == [Float64, String, Float64]
     end
 end