fix transpose error message and clean up code (#2862)

Author: bkamins

src/abstractdataframe/reshape.jl

@@ -542,7 +542,7 @@ Base.similar(v::RepeatedVector, T::Type, dims::Dims) = similar(parent(v), T, dim
 Base.unique(v::RepeatedVector) = unique(parent(v))
 
 Base.transpose(::AbstractDataFrame, args...; kwargs...) =
-    MethodError("`transpose` not defined for `AbstractDataFrame`s. Try `permutedims` instead")
+    throw(ArgumentError("`transpose` not defined for `AbstractDataFrame`s. Try `permutedims` instead"))
 
 """
     permutedims(df::AbstractDataFrame, src_namescol::Union{Int, Symbol, AbstractString},

src/abstractdataframe/sort.jl

@@ -325,7 +325,7 @@ Sort.defalg(df::AbstractDataFrame, col_ord::UserColOrdering, o::Ordering) =
     Sort.defalg(df, col_ord.col, o)
 Sort.defalg(df::AbstractDataFrame, cols, o::Ordering) = Sort.defalg(df)
 Sort.defalg(df::AbstractDataFrame, o::Ordering; alg=nothing, cols=[]) =
-    alg != nothing ? alg : Sort.defalg(df, cols, o)
+    alg !== nothing ? alg : Sort.defalg(df, cols, o)
 
 ########################
 ## Actual sort functions

test/grouping.jl

@@ -1717,14 +1717,14 @@ end
     @test gd[(a=:A, b=1.0)] ≅ gd[1]
 
     @test get(gd, (a=:A, b=1), nothing) ≅ gd[1]
-    @test get(gd, (a=:A, b=3), nothing) == nothing
+    @test get(gd, (a=:A, b=3), nothing) === nothing
     @test get(gd, (:A, 1), nothing) ≅ gd[1]
-    @test get(gd, (:A, 3), nothing) == nothing
+    @test get(gd, (:A, 3), nothing) === nothing
     @test get(gd, first(keys(gd)), gd) ≅ gd[1]
     @test get(gd, Dict("a" => :A, "b" => 1), nothing) ≅ gd[1]
     @test get(gd, Dict(:a => :A, :b => 1), nothing) ≅ gd[1]
     @test get(gd, Dict(:b => 1, :a => :A), nothing) ≅ gd[1]
-    @test get(gd, Dict(:a => :A, :b => 3), nothing) == nothing
+    @test get(gd, Dict(:a => :A, :b => 3), nothing) === nothing
 
     # Wrong values
     @test_throws KeyError gd[(a=:A, b=3)]

test/reshape.jl

@@ -584,7 +584,7 @@ end
 @testset "permutedims" begin
     df1 = DataFrame(a=["x", "y"], b=rand(2), c=[1, 2], d=rand(Bool, 2))
 
-    @test_throws MethodError transpose(df1)
+    @test_throws ArgumentError transpose(df1)
     @test_throws ArgumentError permutedims(df1, :bar)
 
     df1_pd = permutedims(df1, 1)