methodshow: single-line printing for Method by default

Currently `show(::IO, ::Method)` prints the method object in
multiple-line as like:
```julia
julia> only(methods(sin, (Float64,)))
sin(x::T) where T<:Union{Float32, Float64}
     @ Base.Math special/trig.jl:29
```
and this could be confusing when used within a container e.g.:
```julia
julia> Any[only(methods(sin, (Float64,)))]
1-element Vector{Any}:
 sin(x::T) where T<:Union{Float32, Float64}
     @ Base.Math special/trig.jl:29

julia> code_lowered() do; Base.Experimental.@opaque a::Int -> sin(a); end
1-element Vector{Core.CodeInfo}:
 CodeInfo(
1 ─ %1 = Core.apply_type(Core.Tuple, Main.Int)
│   %2 = Core.apply_type(Core.Union)
│   %3 = $(Expr(:new_opaque_closure, :(%1), :(%2), :(Core.Any), opaque closure(...)
     @ Main none:0))
└──      return %3
)
```

This commit refactors the `show` method for `Method` object so that
`show(::IO, ::Method)` prints it within a single line by default and
`show(::IO, ::MIME"text/plain", ::Method)` prints within 2-lines,
that I believe is more aligned with printing implementations for
the other types:
```julia
julia> Any[only(methods(sin, (Float64,)))]
1-element Vector{Any}:
 sin(x::T) where T<:Union{Float32, Float64} @ Base.Math special/trig.jl:29

julia> code_lowered() do; Base.Experimental.@opaque a::Int -> sin(a); end
1-element Vector{Core.CodeInfo}:
 CodeInfo(
1 ─ %1 = Core.apply_type(Core.Tuple, Main.Int)
│   %2 = Core.apply_type(Core.Union)
│   %3 = $(Expr(:new_opaque_closure, :(%1), :(%2), :(Core.Any), opaque closure(...) @ Main none:0))
└──      return %3
)
```

base/errorshow.jl

@@ -346,7 +346,7 @@ function showerror_ambiguous(io::IO, meths, f, args)
  sigfix = Any
  for m in meths
  print(io, " ")
- show(io, m; digit_align_width=-2)
+ show_method(io, m; digit_align_width=0)
  println(io)
  sigfix = typeintersect(m.sig, sigfix)
  end
@@ -543,8 +543,8 @@ function show_method_candidates(io::IO, ex::MethodError, @nospecialize kwargs=()
  println(iob)
 
  m = parentmodule_before_main(method.module)
- color = get!(() -> popfirst!(STACKTRACE_MODULECOLORS), STACKTRACE_FIXEDCOLORS, m)
- print_module_path_file(iob, m, string(file), line, color, 1)
+ modulecolor = get!(() -> popfirst!(STACKTRACE_MODULECOLORS), STACKTRACE_FIXEDCOLORS, m)
+ print_module_path_file(iob, m, string(file), line; modulecolor, digit_align_width = 3)
 
  # TODO: indicate if it's in the wrong world
  push!(lines, (buf, right_matches))
@@ -685,15 +685,15 @@ end
 # Print a stack frame where the module color is determined by looking up the parent module in
 # `modulecolordict`. If the module does not have a color, yet, a new one can be drawn
 # from `modulecolorcycler`.
-function print_stackframe(io, i, frame::StackFrame, n::Int, digit_align_width, modulecolordict, modulecolorcycler)
+function print_stackframe(io, i, frame::StackFrame, n::Int, ndigits_max, modulecolordict, modulecolorcycler)
  m = Base.parentmodule(frame)
  modulecolor = if m !== nothing
  m = parentmodule_before_main(m)
  get!(() -> popfirst!(modulecolorcycler), modulecolordict, m)
  else
  :default
  end
- print_stackframe(io, i, frame, n, digit_align_width, modulecolor)
+ print_stackframe(io, i, frame, n, ndigits_max, modulecolor)
 end
 
 # Gets the topmost parent module that isn't Main
@@ -707,7 +707,7 @@ function parentmodule_before_main(m)
 end
 
 # Print a stack frame where the module color is set manually with `modulecolor`.
-function print_stackframe(io, i, frame::StackFrame, n::Int, digit_align_width, modulecolor)
+function print_stackframe(io, i, frame::StackFrame, n::Int, ndigits_max, modulecolor)
  file, line = string(frame.file), frame.line
  file = fixup_stdlib_path(file)
  stacktrace_expand_basepaths() && (file = something(find_source_file(file), file))
@@ -722,8 +722,10 @@ function print_stackframe(io, i, frame::StackFrame, n::Int, digit_align_width, m
  inlined = getfield(frame, :inlined)
  modul = parentmodule(frame)
 
+ digit_align_width = ndigits_max + 2
+
  # frame number
- print(io, " ", lpad("[" * string(i) * "]", digit_align_width + 2))
+ print(io, " ", lpad("[" * string(i) * "]", digit_align_width))
  print(io, " ")
 
  StackTraces.show_spec_linfo(IOContext(io, :backtrace=>true), frame)
@@ -733,14 +735,14 @@ function print_stackframe(io, i, frame::StackFrame, n::Int, digit_align_width, m
  println(io)
 
  # @ Module path / file : line
- print_module_path_file(io, modul, file, line, modulecolor, digit_align_width)
+ print_module_path_file(io, modul, file, line; modulecolor, digit_align_width)
 
  # inlined
  printstyled(io, inlined ? " [inlined]" : "", color = :light_black)
 end
 
-function print_module_path_file(io, modul, file, line, modulecolor = :light_black, digit_align_width = 0)
- printstyled(io, " " ^ (digit_align_width + 2) * "@", color = :light_black)
+function print_module_path_file(io, modul, file, line; modulecolor = :light_black, digit_align_width = 0)
+ printstyled(io, " " ^ digit_align_width * "@", color = :light_black)
 
  # module
  if modul !== nothing && modulecolor !== nothing

base/methodshow.jl

@@ -205,7 +205,12 @@ function sym_to_string(sym)
  end
 end
 
-function show(io::IO, m::Method; modulecolor = :light_black, digit_align_width = -1)
+# default compact view
+show(io::IO, m::Method; kwargs...) = show_method(IOContext(io, :compact=>true), m; kwargs...)
+
+show(io::IO, ::MIME"text/plain", m::Method; kwargs...) = show_method(io, m; kwargs...)
+
+function show_method(io::IO, m::Method; modulecolor = :light_black, digit_align_width = 1)
  tv, decls, file, line = arg_decl_parts(m)
  sig = unwrap_unionall(m.sig)
  if sig === Tuple
@@ -242,8 +247,12 @@ function show(io::IO, m::Method; modulecolor = :light_black, digit_align_width =
  end
 
  # module & file, re-using function from errorshow.jl
- println(io)
- print_module_path_file(io, m.module, string(file), line, modulecolor, digit_align_width+4)
+ if get(io, :compact, false) # single-line mode
+ print_module_path_file(io, m.module, string(file), line; modulecolor, digit_align_width)
+ else
+ println(io)
+ print_module_path_file(io, m.module, string(file), line; modulecolor, digit_align_width=digit_align_width+4)
+ end
 end
 
 function show_method_list_header(io::IO, ms::MethodList, namefmt::Function)
@@ -313,7 +322,7 @@ function show_method_table(io::IO, ms::MethodList, max::Int=-1, header::Bool=tru
  m = parentmodule_before_main(meth.module)
  get!(() -> popfirst!(STACKTRACE_MODULECOLORS), STACKTRACE_FIXEDCOLORS, m)
  end
- show(io, meth; modulecolor)
+ show_method(io, meth; modulecolor)
 
  file, line = updated_methodloc(meth)
  if last_shown_line_infos !== nothing
@@ -327,7 +336,7 @@ function show_method_table(io::IO, ms::MethodList, max::Int=-1, header::Bool=tru
  if rest > 0
  println(io)
  if rest == 1
- show(io, last)
+ show_method(io, last)
  else
  print(io, "... $rest methods not shown")
  if hasname

test/errorshow.jl

@@ -431,25 +431,25 @@ let err_str,
  Base.stacktrace_contract_userdir() && (sp = Base.contractuser(sp))
 
  @test sprint(show, which(String, Tuple{})) ==
- "String()\n  @ $curmod_str $sp:$(method_defs_lineno + 0)"
+ "String() @ $curmod_str $sp:$(method_defs_lineno + 0)"
  @test sprint(show, which("a", Tuple{})) ==
- "(::String)()\n  @ $curmod_str $sp:$(method_defs_lineno + 1)"
+ "(::String)() @ $curmod_str $sp:$(method_defs_lineno + 1)"
  @test sprint(show, which(EightBitType, Tuple{})) ==
- "$(curmod_prefix)EightBitType()\n  @ $curmod_str $sp:$(method_defs_lineno + 2)"
+ "$(curmod_prefix)EightBitType() @ $curmod_str $sp:$(method_defs_lineno + 2)"
  @test sprint(show, which(reinterpret(EightBitType, 0x54), Tuple{})) ==
- "(::$(curmod_prefix)EightBitType)()\n  @ $curmod_str $sp:$(method_defs_lineno + 3)"
+ "(::$(curmod_prefix)EightBitType)() @ $curmod_str $sp:$(method_defs_lineno + 3)"
  @test sprint(show, which(EightBitTypeT, Tuple{})) ==
- "$(curmod_prefix)EightBitTypeT()\n  @ $curmod_str $sp:$(method_defs_lineno + 4)"
+ "$(curmod_prefix)EightBitTypeT() @ $curmod_str $sp:$(method_defs_lineno + 4)"
  @test sprint(show, which(EightBitTypeT{Int32}, Tuple{})) ==
- "$(curmod_prefix)EightBitTypeT{T}() where T\n  @ $curmod_str $sp:$(method_defs_lineno + 5)"
+ "$(curmod_prefix)EightBitTypeT{T}() where T @ $curmod_str $sp:$(method_defs_lineno + 5)"
  @test sprint(show, which(reinterpret(EightBitTypeT{Int32}, 0x54), Tuple{})) ==
- "(::$(curmod_prefix)EightBitTypeT)()\n  @ $curmod_str $sp:$(method_defs_lineno + 6)"
+ "(::$(curmod_prefix)EightBitTypeT)() @ $curmod_str $sp:$(method_defs_lineno + 6)"
  @test startswith(sprint(show, which(Complex{Int}, Tuple{Int})),
  "Complex{T}(")
  @test startswith(sprint(show, which(getfield(Base, Symbol("@doc")), Tuple{LineNumberNode, Module, Vararg{Any}})),
- "var\"@doc\"(__source__::LineNumberNode, __module__::Module, x...)\n  @ Core boot.jl:")
+ "var\"@doc\"(__source__::LineNumberNode, __module__::Module, x...) @ Core boot.jl:")
  @test startswith(sprint(show, which(FunctionLike(), Tuple{})),
- "(::$(curmod_prefix)FunctionLike)()\n  @ $curmod_str $sp:$(method_defs_lineno + 7)")
+ "(::$(curmod_prefix)FunctionLike)() @ $curmod_str $sp:$(method_defs_lineno + 7)")
  @test startswith(sprint(show, which(StructWithUnionAllMethodDefs{<:Integer}, (Any,))),
  "($(curmod_prefix)StructWithUnionAllMethodDefs{T} where T<:Integer)(x)")
  @test repr("text/plain", FunctionLike()) == "(::$(curmod_prefix)FunctionLike) (generic function with 1 method)"

test/show.jl

@@ -2380,3 +2380,15 @@ Base.show(io::IO, ces::⛵) = Base.print(io, '⛵')
 @test Base.alignment(stdout, ⛵()) == (0, 2)
 @test Base.alignment(IOContext(IOBuffer(), :color=>true), ColoredLetter()) == (0, 1)
 @test Base.alignment(IOContext(IOBuffer(), :color=>false), ColoredLetter()) == (0, 1)
+
+# `show` implementations for `Method`
+let buf = IOBuffer()
+
+ # single line printing by default
+ show(buf, only(methods(sin, (Float64,))))
+ @test !occursin('\n', String(take!(buf)))
+
+ # two-line printing for rich display
+ show(buf, MIME("text/plain"), only(methods(sin, (Float64,))))
+ @test occursin('\n', String(take!(buf)))
+end