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required keyword arguments #586

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merged 8 commits into from
Jul 18, 2018
Merged

required keyword arguments #586

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a9da698
required keyword arguments working
Jul 4, 2018
c6c4be8
using @test_throws and UndeKeywordError now
Jul 4, 2018
51bb759
defining UndefKeywordError only if not yet in Base
Jul 4, 2018
35a2e6c
corrected UndefKeywordError message
Jul 4, 2018
01727dd
added README entry for required keyword arguments
Jul 6, 2018
b9465b2
Merge branch 'master' into master
timziebart Jul 11, 2018
e4dbb1d
Update README.md
timziebart Jul 13, 2018
af801ee
updated README with link
Jul 13, 2018
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18 changes: 18 additions & 0 deletions src/compatmacro.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -25,13 +25,31 @@ else
new_style_typealias(ex) = false
end

if !isdefined(Base, :UndefKeywordError)
struct UndefKeywordError <: Exception
kw
end
Base.showerror(io::IO, e::UndefKeywordError) = print(io, "keyword argument $(e.kw) not assigned")
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Sorry, this should also print the exception type, so

print(io, "UndefKeywordError: keyword argument $(e.kw) not assigned")

as it does on Julia v0.7:

julia> f(;y) = y
f (generic function with 1 method)

julia> f()
ERROR: UndefKeywordError: keyword argument y not assigned

otherwise LGTM

export UndefKeywordError
end

"Convert a functions symbol argument to the corresponding required keyword argument."
function symbol2kw(sym::Symbol)
Expr(:kw, sym, Expr(:call, throw, UndefKeywordError(sym)))
end
symbol2kw(arg) = arg
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@stevengj stevengj Oct 19, 2018 •
edited
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This doesn't handle the case where the argument has a type. It should probably be:

arg2kw(arg, sym) = Expr(:kw, arg, Expr(:call, throw, UndefKeywordError(sym)))
symbol2kw(arg::Symbol) = arg2kw(arg, arg)
symbol2kw(arg::Expr) = isexpr(arg, :(::)) ? arg2kw(arg, arg.args[1]) : arg
symbol2kw(arg) = arg

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(See https://discourse.julialang.org/t/make-function-arguments-positional-or-keyword/2984/35)


function _compat(ex::Expr)
if ex.head === :call
f = ex.args[1]
if VERSION < v"0.6.0-dev.826" && length(ex.args) == 3 && # julia#18510
istopsymbol(withincurly(ex.args[1]), :Base, :Nullable)
ex = Expr(:call, f, ex.args[2], Expr(:call, :(Compat._Nullable_field2), ex.args[3]))
end
if !isdefined(Base, :UndefKeywordError) && length(ex.args) > 1 && isexpr(ex.args[2], :parameters)
params = ex.args[2]
params.args = map(symbol2kw, params.args)
end
elseif ex.head === :curly
f = ex.args[1]
if VERSION < v"0.6.0-dev.2575" #20414
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16 changes: 16 additions & 0 deletions test/runtests.jl
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Expand Up @@ -1856,4 +1856,20 @@ let
@test Compat.split(str, r"\.+:\.+"; limit=3, keepempty=true) == ["a","ba","cba.:.:.dcba.:."]
end

# test required keyword arguments
@compat func1() = 1
@test func1() == 1 # using the function works
@compat func2(x) = x
@test func2(3) == 3 # using the function works
@compat func3(;y) = y
@test func3(y=2) == 2 # using the function works
@test_throws UndefKeywordError func3()
@compat func4(x; z) = x*z
@test func4(2,z=3) == 6 # using the function works
@test_throws UndefKeywordError func4(2)
@compat func5(;x=1, y) = x*y
@test func5(y=3) == 3
@test func5(y=3, x=2) == 6
@test_throws UndefKeywordError func5(x=2)

nothing