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make rand_tangent of struct with no perturbable fields return DoesNotExist #158

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Merged
Parent: Install TagBot as a GitHub Action
merged 1 commit into from
May 7, 2021
Merged

make rand_tangent of struct with no perturbable fields return DoesNotExist #158

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2 changes: 1 addition & 1 deletion Project.toml
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
name = "FiniteDifferences"
uuid = "26cc04aa-876d-5657-8c51-4c34ba976000"
version = "0.12.3"
version = "0.12.4"

[deps]
ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
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7 changes: 6 additions & 1 deletion src/rand_tangent.jl
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Expand Up @@ -33,7 +33,12 @@ function rand_tangent(rng::AbstractRNG, x::T) where {T}
tangents = map(field_names) do field_name
rand_tangent(rng, getfield(x, field_name))
end
return Composite{T}(; NamedTuple{field_names}(tangents)...)
if all(tangent isa DoesNotExist for tangent in tangents)
# if none of my fields can be perturbed then I can't be perturbed
return DoesNotExist()
else
Composite{T}(; NamedTuple{field_names}(tangents)...)
end
else
return NO_FIELDS
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The outer if here that gives us the NO_FIELDS would be able to be removed if we replaced NO_FIELDS with DoesNotExist().
Since then we would be in the case that all the fields (of which there are none) subtype DoesNotExist.
Vacuous truth.

JuliaDiff/ChainRulesCore.jl#175 (comment)

end
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6 changes: 5 additions & 1 deletion test/rand_tangent.jl
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Expand Up @@ -32,9 +32,13 @@ using FiniteDifferences: rand_tangent
((a=5.0, b=1), Composite{NamedTuple{(:a, :b), Tuple{Float64, Int}}}),

# structs.
(sin, typeof(NO_FIELDS)),
(Foo(5.0, 4, rand(rng, 3)), Composite{Foo}),
(Foo(4.0, 3, Foo(5.0, 2, 4)), Composite{Foo}),
(sin, typeof(NO_FIELDS)),
# all fields DoesNotExist implies DoesNotExist
(Pair(:a, "b"), DoesNotExist),
(1:10, DoesNotExist),
(1:2:10, DoesNotExist),

# LinearAlgebra types (also just structs).
(
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