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Merged
LilithHafner merged 2 commits into from
Apr 25, 2025
Merged

Export fieldindex #58119

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db7a56c
Export `fieldindex`
PatrickHaecker Apr 15, 2025
dd20a7d
Add news entry about exported fieldindex
PatrickHaecker Apr 25, 2025
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2 changes: 2 additions & 0 deletions NEWS.md
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Expand Up @@ -24,6 +24,8 @@ Build system changes
New library functions
---------------------

* Exporting function `fieldindex` to get the index of a struct's field ([#58119]).

New library features
--------------------

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1 change: 1 addition & 0 deletions base/exports.jl
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Expand Up @@ -807,6 +807,7 @@ export
fieldoffset,
fieldname,
fieldnames,
fieldindex,
fieldcount,
fieldtypes,
hasfield,
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12 changes: 9 additions & 3 deletions base/runtime_internals.jl
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Expand Up @@ -1057,7 +1057,7 @@ String
fieldtype

"""
Base.fieldindex(T, name::Symbol, err:Bool=true)
fieldindex(T, name::Symbol, err:Bool=true)

Get the index of a named field, throwing an error if the field does not exist (when err==true)
or returning 0 (when err==false).
Expand All @@ -1069,14 +1069,20 @@ julia> struct Foo
y::String
end

julia> Base.fieldindex(Foo, :z)
julia> fieldindex(Foo, :y)
2

julia> fieldindex(Foo, :z)
ERROR: FieldError: type Foo has no field `z`, available fields: `x`, `y`
Stacktrace:
[...]

julia> Base.fieldindex(Foo, :z, false)
julia> fieldindex(Foo, :z, false)
0
```

!!! compat "Julia 1.13"
This function is exported as of Julia 1.13.
"""
function fieldindex(T::DataType, name::Symbol, err::Bool=true)
return err ? _fieldindex_maythrow(T, name) : _fieldindex_nothrow(T, name)
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1 change: 1 addition & 0 deletions doc/src/base/base.md
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Expand Up @@ -207,6 +207,7 @@ Base.isstructtype
Base.nameof(::DataType)
Base.fieldnames
Base.fieldname
Base.fieldindex
Core.fieldtype
Base.fieldtypes
Base.fieldcount
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4 changes: 4 additions & 0 deletions test/reflection.jl
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Expand Up @@ -361,6 +361,10 @@ tlayout = TLayout(5,7,11)
@test fieldtype(Union{Tuple{Char},Tuple{Char,Char}},2) === Char
@test_throws BoundsError fieldtype(Union{Tuple{Char},Tuple{Char,Char}},3)

@test [fieldindex(TLayout, i) for i = (:x, :y, :z)] == [1, 2, 3]
@test fieldname(TLayout, fieldindex(TLayout, :z)) === :z
@test fieldindex(TLayout, fieldname(TLayout, 3)) === 3

@test fieldnames(NTuple{3, Int}) == ntuple(i -> fieldname(NTuple{3, Int}, i), 3) == (1, 2, 3)
@test_throws ArgumentError fieldnames(Union{})
@test_throws BoundsError fieldname(NTuple{3, Int}, 0)
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