Merge pull request JuliaLang#16651 from JuliaLang/jb/fix16649

implement output limiting for single-line array showing

base/show.jl

@@ -1442,24 +1442,46 @@ end
 `print_matrix_repr(io, X)` prints matrix X with opening and closing square brackets.
 """
 function print_matrix_repr(io, X::AbstractArray)
+ limit = get(io, :limit, false)::Bool
  compact, prefix = array_eltype_show_how(X)
  if compact && !haskey(io, :compact)
  io = IOContext(io, :compact => compact)
  end
+ nr, nc = size(X,1), size(X,2)
+ rdots, cdots = false, false
+ rr1, rr2 = 1:nr, 1:0
+ cr1, cr2 = 1:nc, 1:0
+ if limit
+ if nr > 4
+ rr1, rr2 = 1:2, nr-1:nr
+ rdots = true
+ end
+ if nc > 4
+ cr1, cr2 = 1:2, nc-1:nc
+ cdots = true
+ end
+ end
  print(io, prefix, "[")
- for i=1:size(X,1)
- for j=1:size(X,2)
- j > 1 && print(io, " ")
- if !isassigned(X,i,j)
- print(io, undef_ref_str)
- else
- el = X[i,j]
- show(io, el)
+ for rr in (rr1, rr2)
+ for i in rr
+ for cr in (cr1, cr2)
+ for j in cr
+ j > first(cr) && print(io, " ")
+ if !isassigned(X,i,j)
+ print(io, undef_ref_str)
+ else
+ el = X[i,j]
+ show(io, el)
+ end
+ end
+ if last(cr) == nc
+ i < nr && print(io, "; ")
+ elseif cdots
+ print(io, " \u2026 ")
+ end
  end
  end
- if i < size(X,1)
- print(io, "; ")
- end
+ last(rr) != nr && rdots && print(io, "\u2026 ; ")
  end
  print(io, "]")
 end

test/show.jl

@@ -443,3 +443,7 @@ end
 # parameter names.
 @test string(Array) == "Array{T,N}"
 @test string(Tuple{Array}) == "Tuple{Array}"
+
+# PR #16651
+@test !contains(repr(ones(10,10)), "\u2026")
+@test contains(sprint((io,x)->show(IOContext(io,:limit=>true), x), ones(30,30)), "\u2026")