[BREAKING] deprecate DataFrame constructors (#2464)

NEWS.md

@@ -91,6 +91,8 @@
 ## Deprecated
 
 * `DataFrame!` is now deprecated ([#2338](https://github.com/JuliaData/DataFrames.jl/pull/2338))
+* several in-standard `DataFrame` constructors are now deprecated
+  ([#2464](https://github.com/JuliaData/DataFrames.jl/pull/2464))
 * all old deprecations now throw an error
   ([#2350](https://github.com/JuliaData/DataFrames.jl/pull/2350))
 

Project.toml

@@ -44,5 +44,5 @@ Missings = "0.4.2"
 PooledArrays = "0.5"
 Reexport = "0.1, 0.2"
 SortingAlgorithms = "0.1, 0.2, 0.3"
-Tables = "1"
+Tables = "1.1"
 TableTraits = "0.4, 1"

src/deprecated.jl

@@ -105,3 +105,43 @@ function categorical!(df::DataFrame, cols::Union{Type, Nothing}=nothing;
     end
     return transform!(df, names(df, cols) .=> (x -> categorical(x, compress=compress)), renamecols=false)
 end
+
+@deprecate DataFrame(pairs::NTuple{N, Pair}; makeunique::Bool=false,
+          copycols::Bool=true) where {N} DataFrame(pairs..., makeunique=makeunique, copycols=copycols)
+@deprecate DataFrame(columns::NTuple{N, AbstractVector}, cnames::NTuple{N, Symbol}; makeunique::Bool=false,
+          copycols::Bool=true) where {N} DataFrame(collect(columns), collect(cnames);
+              makeunique=makeunique, copycols=copycols)
+@deprecate DataFrame(columns::NTuple{N, AbstractVector}, cnames::NTuple{N, AbstractString}; makeunique::Bool=false,
+                     copycols::Bool=true) where {N} DataFrame(collect(columns), [Symbol(c) for c in cnames];
+                                                              makeunique=makeunique, copycols=copycols)
+@deprecate DataFrame(columns::NTuple{N, AbstractVector};
+                     copycols::Bool=true) where {N} DataFrame(collect(columns),
+                                                              Symbol.(:x, 1:length(columns)), copycols=copycols)
+
+# this deprecation is very important, becuase without it users will
+# get strange results with old code as described in https://github.com/JuliaData/Tables.jl/issues/208
+@deprecate DataFrame(columns::AbstractVector{<:AbstractVector}; makeunique::Bool=false,
+                     copycols::Bool=true) DataFrame(columns, :auto, copycols=copycols)
+
+@deprecate DataFrame(columns::AbstractMatrix) DataFrame(columns, :auto)
+
+function DataFrame(column_eltypes::AbstractVector{T}, cnames::AbstractVector{Symbol},
+                   nrows::Integer=0; makeunique::Bool=false)::DataFrame where T<:Type
+    Base.depwarn("`DataFrame` constructor with passed eltypes is deprecated. " *
+                 "Pass explicitly created columns to a `DataFrame` constructor instead.",
+                     :DataFrame)
+    columns = AbstractVector[elty >: Missing ?
+                             fill!(Tables.allocatecolumn(elty, nrows), missing) :
+                             Tables.allocatecolumn(elty, nrows)
+                             for elty in column_eltypes]
+    return DataFrame(columns, Index(convert(Vector{Symbol}, cnames),
+                     makeunique=makeunique), copycols=false)
+end
+
+DataFrame(column_eltypes::AbstractVector{<:Type},
+          cnames::AbstractVector{<:AbstractString},
+          nrows::Integer=0; makeunique::Bool=false) =
+    DataFrame(column_eltypes, Symbol.(cnames), nrows; makeunique=makeunique)
+
+import Base: convert
+@deprecate convert(::Type{DataFrame}, A::AbstractMatrix) DataFrame(Tables.table(A, header=Symbol.(:x, axes(A, 2))))

src/other/tables.jl

@@ -43,11 +43,11 @@ fromcolumns(x, names; copycols::Bool=true) =
               copycols=copycols)
 
 function DataFrame(x::T; copycols::Bool=true) where {T}
-    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)
+    if !Tables.istable(x) && x isa AbstractVector && !isempty(x)
+        # here we handle eltypes not specific enough to be dispatched
+        # to other DataFrames constructors taking vector of `Pair`s
+        if all(v -> v isa Pair{Symbol, <:AbstractVector}, x) ||
+            all(v -> v isa Pair{<:AbstractString, <:AbstractVector}, x)
             return DataFrame(AbstractVector[last(v) for v in x], [first(v) for v in x],
                              copycols=copycols)
         end