Support testing mutating functions in frule_test (#79)

* Add failing test for mutating function

* Support mutation in frule_test

* Update src/testers.jl

Co-authored-by: willtebbutt <[email protected]>

* Update src/testers.jl

Co-authored-by: willtebbutt <[email protected]>

* Revert "Update src/testers.jl"

This reverts commit 4f77a54.

* Revert "Update src/testers.jl"

This reverts commit 2f4e143.

* Increment version number

Co-authored-by: willtebbutt <[email protected]>

Author: sethaxen

Project.toml

@@ -1,6 +1,6 @@
 name = "ChainRulesTestUtils"
 uuid = "cdddcdb0-9152-4a09-a978-84456f9df70a"
-version = "0.5.4"
+version = "0.5.5"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"

src/testers.jl

@@ -183,16 +183,16 @@ All keyword arguments except for `fdm` and `fkwargs` are passed to `isapprox`.
 function frule_test(f, xẋs::Tuple{Any, Any}...; rtol=1e-9, atol=1e-9, fdm=_fdm, fkwargs=NamedTuple(), kwargs...)
     _ensure_not_running_on_functor(f, "frule_test")
     xs, ẋs = first.(xẋs), last.(xẋs)
-    Ω_ad, dΩ_ad = frule((NO_FIELDS, ẋs...), f, xs...; fkwargs...)
-    Ω = f(xs...; fkwargs...)
+    Ω_ad, dΩ_ad = frule((NO_FIELDS, deepcopy(ẋs)...), f, deepcopy(xs)...; deepcopy(fkwargs)...)
+    Ω = f(deepcopy(xs)...; deepcopy(fkwargs)...)
     # if equality check fails, check approximate equality
     # use collect so can do vector equality
     # TODO: add isapprox replacement that works for more types
     @test Ω_ad == Ω || isapprox(collect(Ω_ad), collect(Ω); rtol=rtol, atol=atol)
 
     ẋs_is_ignored = ẋs .== nothing
     # Correctness testing via finite differencing.
-    dΩ_fd = _make_jvp_call(fdm, (xs...) -> f(xs...; fkwargs...), xs, ẋs, ẋs_is_ignored)
+    dΩ_fd = _make_jvp_call(fdm, (xs...) -> f(deepcopy(xs)...; deepcopy(fkwargs)...), xs, ẋs, ẋs_is_ignored)
     @test isapprox(
         collect(extern.(dΩ_ad)),  # Use collect so can use vector equality
         collect(dΩ_fd);

test/testers.jl

@@ -7,6 +7,11 @@ sinconj(x) = sin(x)
 
 primalapprox(x) = x
 
+function finplace!(x; y = [1])
+    y[1] = 2
+    x .*= y[1]
+    return x
+end
 
 @testset "testers.jl" begin
     @testset "test_scalar" begin
@@ -261,6 +266,24 @@ primalapprox(x) = x
         rrule_test(primalapprox, randn(), (randn(), randn()); atol = 1e-6)
     end
 
+    @testset "frule with mutation" begin
+        function ChainRulesCore.frule((_, ẋ), ::typeof(finplace!), x; y = [1])
+            y[1] *= 2
+            x .*= y[1]
+            ẋ .*= 2 # hardcoded to match y defined below
+            return x, ẋ
+        end
+
+        x = randn(3)
+        ẋ = [4.0, 5.0, 6.0]
+        xcopy, ẋcopy = copy(x), copy(ẋ)
+        y = [1, 2]
+        frule_test(finplace!, (x, ẋ); fkwargs=(y = y,))
+        @test x == xcopy
+        @test ẋ == ẋcopy
+        @test y == [1, 2]
+    end
+
     @testset "TestIterator input" begin
         function iterfun(iter)
             state = iterate(iter)