correctly use dotview instead of maybeview in broadcasting contexts

src/deprecated.jl

@@ -1532,8 +1532,13 @@ function Base.setindex!(df::DataFrame, v, ::Colon, col_inds)
     df
 end
 
+function Base.dotview(df::AbstractDataFrame, col::ColumnIndex)
+    Base.depwarn("in broadcasted assignment use `df[:, col]` instead of `df[col]`", :dotview)
+    @view df[:, col]
+end
+
 import Base: setproperty!
 @deprecate setproperty!(df::DataFrame, col_ind::Symbol, v) (df[!, col_ind] .= v)
 @deprecate setproperty!(df::SubDataFrame, col_ind::Symbol, v) (df[:, col_ind] .= v)
 
-@deprecate eltypes(df::AbstractDataFrame) eltype.(eachcol(df))
+@deprecate eltypes(df::AbstractDataFrame) eltype.(eachcol(df))

src/other/broadcasting.jl

@@ -96,7 +96,7 @@ Base.maybeview(df::AbstractDataFrame, idx::CartesianIndex{2}) = df[idx]
 Base.maybeview(df::AbstractDataFrame, row::Integer, col::ColumnIndex) = df[row, col]
 Base.maybeview(df::AbstractDataFrame, rows, cols) = view(df, rows, cols)
 
-function Base.maybeview(df::DataFrame, ::typeof(!), cols)
+function Base.dotview(df::DataFrame, ::typeof(!), cols)
     if !(cols isa ColumnIndex)
         return ColReplaceDataFrame(df, index(df)[cols])
     end
@@ -106,7 +106,7 @@ function Base.maybeview(df::DataFrame, ::typeof(!), cols)
     LazyNewColDataFrame(df, cols)
 end
 
-Base.maybeview(df::SubDataFrame, ::typeof(!), idxs) =
+Base.dotview(df::SubDataFrame, ::typeof(!), idxs) =
     throw(ArgumentError("broadcasting with ! row selector is not allowed for SubDataFrame"))
 
 function Base.copyto!(lazydf::LazyNewColDataFrame, bc::Base.Broadcast.Broadcasted{T}) where T

test/broadcasting.jl

@@ -1479,4 +1479,15 @@ end
     @test df == f_identity.(df)
 end
 
+@testset "@views on df[!, col]" begin
+    df = DataFrame(ones(3, 4))
+    @views df[!, 1] .+= 1
+    @test df[!, 1] == [2.0, 2.0, 2.0]
+    @views df[:, 2] .= df[!, 4] .+ df[!, 3]
+    @test df[!, 2] == [2.0, 2.0, 2.0]
+
+    # make sure we do not mess with maybeview
+    @test @views typeof(df[!, 1:2]) <: SubDataFrame
+end
+
 end # module