From d905ca7385795fbd29cd28da29787a6b1c0a91e2 Mon Sep 17 00:00:00 2001
From: Seth Axen <seth.axen@gmail.com>
Date: Mon, 6 Jul 2020 16:59:19 -0700
Subject: [PATCH 1/3] =?UTF-8?q?Handle=20empty=20primal=20in=20j=E2=80=B2vp?=
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---
 src/grad.jl | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/grad.jl b/src/grad.jl
index 461f0c11..cb1e1894 100644
--- a/src/grad.jl
+++ b/src/grad.jl
@@ -76,6 +76,7 @@ end
 j′vp(fdm, f, ȳ, xs...) = j′vp(fdm, xs->f(xs...), ȳ, xs)[1]
 
 function _j′vp(fdm, f, ȳ::Vector{<:Real}, x::Vector{<:Real})
+    isempty(x) && return eltype(ȳ)[] # if x is empty, then so is the jacobian and x̄
     return transpose(first(jacobian(fdm, f, x))) * ȳ
 end
 

From 99ade74be1a9ea070a8355db5ed1864ba781d19f Mon Sep 17 00:00:00 2001
From: Seth Axen <seth.axen@gmail.com>
Date: Mon, 6 Jul 2020 16:59:46 -0700
Subject: [PATCH 2/3] =?UTF-8?q?Test=20j=E2=80=B2vp=20on=20empty=20primals?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 test/grad.jl | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/test/grad.jl b/test/grad.jl
index 44097ceb..d7c71e57 100644
--- a/test/grad.jl
+++ b/test/grad.jl
@@ -118,15 +118,17 @@ using FiniteDifferences: grad, jacobian, _jvp, jvp, j′vp, _j′vp, to_vec
     end
 
     @testset "j′vp(::$T)" for T in (Float64,)
-        rng, N, M, fdm = MersenneTwister(123456), 2, 3, central_fdm(5, 1)
-        x, y = randn(rng, T, N), randn(rng, T, M)
-        z̄ = randn(rng, T, N + M)
-        xy = vcat(x, y)
-        x̄ȳ_manual = j′vp(fdm, xy->sin.(xy), z̄, xy)[1]
-        x̄ȳ_auto = j′vp(fdm, x->sin.(vcat(x[1], x[2])), z̄, (x, y))[1]
-        x̄ȳ_multi = j′vp(fdm, (x, y)->sin.(vcat(x, y)), z̄, x, y)
-        @test x̄ȳ_manual ≈ vcat(x̄ȳ_auto...)
-        @test x̄ȳ_manual ≈ vcat(x̄ȳ_multi...)
+        rng, fdm = MersenneTwister(123456), central_fdm(5, 1)
+        @testset "x with length $N, y with length $M" for (N, M) in ((2, 3), (0, 0), (0, 3))
+            x, y = randn(rng, T, N), randn(rng, T, M)
+            z̄ = randn(rng, T, N + M)
+            xy = vcat(x, y)
+            x̄ȳ_manual = j′vp(fdm, xy->sin.(xy), z̄, xy)[1]
+            x̄ȳ_auto = j′vp(fdm, x->sin.(vcat(x[1], x[2])), z̄, (x, y))[1]
+            x̄ȳ_multi = j′vp(fdm, (x, y)->sin.(vcat(x, y)), z̄, x, y)
+            @test x̄ȳ_manual ≈ vcat(x̄ȳ_auto...)
+            @test x̄ȳ_manual ≈ vcat(x̄ȳ_multi...)
+        end
     end
 
     # Tests for complex numbers, to prevent regressions against

From 617aa73ab5864f2ccb6158aa64f67185bb346d1d Mon Sep 17 00:00:00 2001
From: Seth Axen <seth.axen@gmail.com>
Date: Mon, 6 Jul 2020 17:00:01 -0700
Subject: [PATCH 3/3] Increment version number

---
 Project.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Project.toml b/Project.toml
index e9373264..06f6ced5 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "FiniteDifferences"
 uuid = "26cc04aa-876d-5657-8c51-4c34ba976000"
-version = "0.10.2"
+version = "0.10.4"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"