@show displays unnecessary parentheses for nested structs

[GregPlowman]

The display using @show for nested structs has parentheses, which seems like clutter to me.
I like the v0.6 behavior better.

struct Foo3 x::Int end
struct Foo2 x::Foo3 end
struct Foo1 x::Foo2 end

foo1 = Foo1(Foo2(Foo3(42)))
@show foo1.x
@show foo1.x.x
@show foo1.x.x.x

For Julia v0.6.4:

foo1.x = Foo2(Foo3(42))
foo1.x.x = Foo3(42)
foo1.x.x.x = 42

For Julia v0.7.0, v1.0.3, v1.1.0:

foo1.x = Foo2(Foo3(42))
(foo1.x).x = Foo3(42)
((foo1.x).x).x = 42

[inkydragon]

those code make the difference, and it is add by pr #24994

julia/base/show.jl

Lines 1123 to 1126 in a03da73

	parens = !is_quoted(item) && !(item isa Symbol && isidentifier(item))
	parens && print(io, '(')
	show_unquoted(io, item, indent)
	parens && print(io, ')')

.

---

How to find this?

julia> VERSION
v"0.6.4"

julia> struct Foo3 x::Int end
julia> struct Foo2 x::Foo3 end
julia> struct Foo1 x::Foo2 end
julia> foo1 = Foo1(Foo2(Foo3(42)))
Foo1(Foo2(Foo3(42)))

julia> @show foo1.x.x.x
foo1.x.x.x = 42
42

julia> VERSION
v"1.0.3"

julia> struct Foo3 x::Int end
julia> struct Foo2 x::Foo3 end
julia> struct Foo1 x::Foo2 end
julia> foo1 = Foo1(Foo2(Foo3(42)))
Foo1(Foo2(Foo3(42)))

julia> @show foo1.x.x.x
((foo1.x).x).x = 42
42

julia> @edit @show foo1.x.x.x

Then search macro show you will find @show's definition.

julia/base/show.jl

Lines 568 to 572 in a03da73

	macro show(exs...)
	blk = Expr(:block)
	for ex in exs
	push!(blk.args, :(println($(sprint(show_unquoted,ex)*" = "),
	repr(begin value=$(esc(ex)) end))))

have a look and test code in REPL

julia> sprint(Base.show_unquoted, :(foo1.x.x.x))
"((foo1.x).x).x"

search show_unquoted

julia/base/show.jl

Lines 763 to 767 in a03da73

	print( io::IO, ex::ExprNode) = (show_unquoted(io, ex, 0, -1); nothing)
	show( io::IO, ex::ExprNode) = show_unquoted_quote_expr(io, ex, 0, -1)
	show_unquoted(io::IO, ex) = show_unquoted(io, ex, 0, 0)
	show_unquoted(io::IO, ex, indent::Int) = show_unquoted(io, ex, indent, 0)
	show_unquoted(io::IO, ex, ::Int,::Int) = show(io, ex)

continue test

julia> Base.show_unquoted(stdout, :(foo1.x.x.x))
((foo1.x).x).x

julia> typeof(:(foo1.x.x.x))
Expr

julia> methods(Base.show_unquoted, (IO, Expr))
# 1 method for generic function "show_unquoted":[1] show_unquoted(io::IO, ex) in Base at show.jl:751

The same

julia/base/show.jl

Lines 765 to 767 in a03da73

	show_unquoted(io::IO, ex) = show_unquoted(io, ex, 0, 0)
	show_unquoted(io::IO, ex, indent::Int) = show_unquoted(io, ex, indent, 0)
	show_unquoted(io::IO, ex, ::Int,::Int) = show(io, ex)

julia> Base.show_unquoted(stdout, :(foo1.x.x.x), 0,0)
((foo1.x).x).x
julia> methods(show_unquoted, (IO, Expr, Int, Int))
# 1 method for generic function "show_unquoted":[1] show_unquoted(io::IO, ex::Expr, indent::Int64, prec::Int64) in Base at show.jl:1096

and finally you find those code

julia/base/show.jl

Lines 1114 to 1128 in a03da73

	function show_unquoted(io::IO, ex::Expr, indent::Int, prec::Int)
	head, args, nargs = ex.head, ex.args, length(ex.args)
	unhandled = false
	# dot (i.e. "x.y"), but not compact broadcast exps
	if head === :(.) && (nargs != 2 || !is_expr(args[2], :tuple))
	if nargs == 2 && is_quoted(args[2])
	item = args[1]
	# field
	field = unquoted(args[2])
	parens = !is_quoted(item) && !(item isa Symbol && isidentifier(item))
	parens && print(io, '(')
	show_unquoted(io, item, indent)
	parens && print(io, ')')
	# .
	print(io, '.')

[JeffBezanson]

Thanks! Before the . we should allow . expressions to be printed without parens. Care to make a PR for that?